1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
use super::Error;
use crate::{
    back,
    proc::{self, NameKey},
    valid, Handle, Module, ShaderStage, TypeInner,
};
use std::fmt::Write;

/// Shorthand result used internally by the backend
type BackendResult = Result<(), Error>;

/// WGSL [attribute](https://gpuweb.github.io/gpuweb/wgsl/#attributes)
enum Attribute {
    Binding(u32),
    BuiltIn(crate::BuiltIn),
    Group(u32),
    Invariant,
    Interpolate(Option<crate::Interpolation>, Option<crate::Sampling>),
    Location(u32),
    SecondBlendSource,
    Stage(ShaderStage),
    WorkGroupSize([u32; 3]),
}

/// The WGSL form that `write_expr_with_indirection` should use to render a Naga
/// expression.
///
/// Sometimes a Naga `Expression` alone doesn't provide enough information to
/// choose the right rendering for it in WGSL. For example, one natural WGSL
/// rendering of a Naga `LocalVariable(x)` expression might be `&x`, since
/// `LocalVariable` produces a pointer to the local variable's storage. But when
/// rendering a `Store` statement, the `pointer` operand must be the left hand
/// side of a WGSL assignment, so the proper rendering is `x`.
///
/// The caller of `write_expr_with_indirection` must provide an `Expected` value
/// to indicate how ambiguous expressions should be rendered.
#[derive(Clone, Copy, Debug)]
enum Indirection {
    /// Render pointer-construction expressions as WGSL `ptr`-typed expressions.
    ///
    /// This is the right choice for most cases. Whenever a Naga pointer
    /// expression is not the `pointer` operand of a `Load` or `Store`, it
    /// must be a WGSL pointer expression.
    Ordinary,

    /// Render pointer-construction expressions as WGSL reference-typed
    /// expressions.
    ///
    /// For example, this is the right choice for the `pointer` operand when
    /// rendering a `Store` statement as a WGSL assignment.
    Reference,
}

bitflags::bitflags! {
    #[cfg_attr(feature = "serialize", derive(serde::Serialize))]
    #[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
    pub struct WriterFlags: u32 {
        /// Always annotate the type information instead of inferring.
        const EXPLICIT_TYPES = 0x1;
    }
}

pub struct Writer<W> {
    out: W,
    flags: WriterFlags,
    names: crate::FastHashMap<NameKey, String>,
    namer: proc::Namer,
    named_expressions: crate::NamedExpressions,
    ep_results: Vec<(ShaderStage, Handle<crate::Type>)>,
}

impl<W: Write> Writer<W> {
    pub fn new(out: W, flags: WriterFlags) -> Self {
        Writer {
            out,
            flags,
            names: crate::FastHashMap::default(),
            namer: proc::Namer::default(),
            named_expressions: crate::NamedExpressions::default(),
            ep_results: vec![],
        }
    }

    fn reset(&mut self, module: &Module) {
        self.names.clear();
        self.namer.reset(
            module,
            crate::keywords::wgsl::RESERVED,
            // an identifier must not start with two underscore
            &[],
            &[],
            &["__"],
            &mut self.names,
        );
        self.named_expressions.clear();
        self.ep_results.clear();
    }

    fn is_builtin_wgsl_struct(&self, module: &Module, handle: Handle<crate::Type>) -> bool {
        module
            .special_types
            .predeclared_types
            .values()
            .any(|t| *t == handle)
    }

    pub fn write(&mut self, module: &Module, info: &valid::ModuleInfo) -> BackendResult {
        if !module.overrides.is_empty() {
            return Err(Error::Unimplemented(
                "Pipeline constants are not yet supported for this back-end".to_string(),
            ));
        }

        self.reset(module);

        // Save all ep result types
        for ep in &module.entry_points {
            if let Some(ref result) = ep.function.result {
                self.ep_results.push((ep.stage, result.ty));
            }
        }

        // Write all structs
        for (handle, ty) in module.types.iter() {
            if let TypeInner::Struct { ref members, .. } = ty.inner {
                {
                    if !self.is_builtin_wgsl_struct(module, handle) {
                        self.write_struct(module, handle, members)?;
                        writeln!(self.out)?;
                    }
                }
            }
        }

        // Write all named constants
        let mut constants = module
            .constants
            .iter()
            .filter(|&(_, c)| c.name.is_some())
            .peekable();
        while let Some((handle, _)) = constants.next() {
            self.write_global_constant(module, handle)?;
            // Add extra newline for readability on last iteration
            if constants.peek().is_none() {
                writeln!(self.out)?;
            }
        }

        // Write all globals
        for (ty, global) in module.global_variables.iter() {
            self.write_global(module, global, ty)?;
        }

        if !module.global_variables.is_empty() {
            // Add extra newline for readability
            writeln!(self.out)?;
        }

        // Write all regular functions
        for (handle, function) in module.functions.iter() {
            let fun_info = &info[handle];

            let func_ctx = back::FunctionCtx {
                ty: back::FunctionType::Function(handle),
                info: fun_info,
                expressions: &function.expressions,
                named_expressions: &function.named_expressions,
            };

            // Write the function
            self.write_function(module, function, &func_ctx)?;

            writeln!(self.out)?;
        }

        // Write all entry points
        for (index, ep) in module.entry_points.iter().enumerate() {
            let attributes = match ep.stage {
                ShaderStage::Vertex | ShaderStage::Fragment => vec![Attribute::Stage(ep.stage)],
                ShaderStage::Compute => vec![
                    Attribute::Stage(ShaderStage::Compute),
                    Attribute::WorkGroupSize(ep.workgroup_size),
                ],
            };

            self.write_attributes(&attributes)?;
            // Add a newline after attribute
            writeln!(self.out)?;

            let func_ctx = back::FunctionCtx {
                ty: back::FunctionType::EntryPoint(index as u16),
                info: info.get_entry_point(index),
                expressions: &ep.function.expressions,
                named_expressions: &ep.function.named_expressions,
            };
            self.write_function(module, &ep.function, &func_ctx)?;

            if index < module.entry_points.len() - 1 {
                writeln!(self.out)?;
            }
        }

        Ok(())
    }

    /// Helper method used to write struct name
    ///
    /// # Notes
    /// Adds no trailing or leading whitespace
    fn write_struct_name(&mut self, module: &Module, handle: Handle<crate::Type>) -> BackendResult {
        if module.types[handle].name.is_none() {
            if let Some(&(stage, _)) = self.ep_results.iter().find(|&&(_, ty)| ty == handle) {
                let name = match stage {
                    ShaderStage::Compute => "ComputeOutput",
                    ShaderStage::Fragment => "FragmentOutput",
                    ShaderStage::Vertex => "VertexOutput",
                };

                write!(self.out, "{name}")?;
                return Ok(());
            }
        }

        write!(self.out, "{}", self.names[&NameKey::Type(handle)])?;

        Ok(())
    }

    /// Helper method used to write
    /// [functions](https://gpuweb.github.io/gpuweb/wgsl/#functions)
    ///
    /// # Notes
    /// Ends in a newline
    fn write_function(
        &mut self,
        module: &Module,
        func: &crate::Function,
        func_ctx: &back::FunctionCtx<'_>,
    ) -> BackendResult {
        let func_name = match func_ctx.ty {
            back::FunctionType::EntryPoint(index) => &self.names[&NameKey::EntryPoint(index)],
            back::FunctionType::Function(handle) => &self.names[&NameKey::Function(handle)],
        };

        // Write function name
        write!(self.out, "fn {func_name}(")?;

        // Write function arguments
        for (index, arg) in func.arguments.iter().enumerate() {
            // Write argument attribute if a binding is present
            if let Some(ref binding) = arg.binding {
                self.write_attributes(&map_binding_to_attribute(binding))?;
            }
            // Write argument name
            let argument_name = &self.names[&func_ctx.argument_key(index as u32)];

            write!(self.out, "{argument_name}: ")?;
            // Write argument type
            self.write_type(module, arg.ty)?;
            if index < func.arguments.len() - 1 {
                // Add a separator between args
                write!(self.out, ", ")?;
            }
        }

        write!(self.out, ")")?;

        // Write function return type
        if let Some(ref result) = func.result {
            write!(self.out, " -> ")?;
            if let Some(ref binding) = result.binding {
                self.write_attributes(&map_binding_to_attribute(binding))?;
            }
            self.write_type(module, result.ty)?;
        }

        write!(self.out, " {{")?;
        writeln!(self.out)?;

        // Write function local variables
        for (handle, local) in func.local_variables.iter() {
            // Write indentation (only for readability)
            write!(self.out, "{}", back::INDENT)?;

            // Write the local name
            // The leading space is important
            write!(self.out, "var {}: ", self.names[&func_ctx.name_key(handle)])?;

            // Write the local type
            self.write_type(module, local.ty)?;

            // Write the local initializer if needed
            if let Some(init) = local.init {
                // Put the equal signal only if there's a initializer
                // The leading and trailing spaces aren't needed but help with readability
                write!(self.out, " = ")?;

                // Write the constant
                // `write_constant` adds no trailing or leading space/newline
                self.write_expr(module, init, func_ctx)?;
            }

            // Finish the local with `;` and add a newline (only for readability)
            writeln!(self.out, ";")?
        }

        if !func.local_variables.is_empty() {
            writeln!(self.out)?;
        }

        // Write the function body (statement list)
        for sta in func.body.iter() {
            // The indentation should always be 1 when writing the function body
            self.write_stmt(module, sta, func_ctx, back::Level(1))?;
        }

        writeln!(self.out, "}}")?;

        self.named_expressions.clear();

        Ok(())
    }

    /// Helper method to write a attribute
    fn write_attributes(&mut self, attributes: &[Attribute]) -> BackendResult {
        for attribute in attributes {
            match *attribute {
                Attribute::Location(id) => write!(self.out, "@location({id}) ")?,
                Attribute::SecondBlendSource => write!(self.out, "@second_blend_source ")?,
                Attribute::BuiltIn(builtin_attrib) => {
                    let builtin = builtin_str(builtin_attrib)?;
                    write!(self.out, "@builtin({builtin}) ")?;
                }
                Attribute::Stage(shader_stage) => {
                    let stage_str = match shader_stage {
                        ShaderStage::Vertex => "vertex",
                        ShaderStage::Fragment => "fragment",
                        ShaderStage::Compute => "compute",
                    };
                    write!(self.out, "@{stage_str} ")?;
                }
                Attribute::WorkGroupSize(size) => {
                    write!(
                        self.out,
                        "@workgroup_size({}, {}, {}) ",
                        size[0], size[1], size[2]
                    )?;
                }
                Attribute::Binding(id) => write!(self.out, "@binding({id}) ")?,
                Attribute::Group(id) => write!(self.out, "@group({id}) ")?,
                Attribute::Invariant => write!(self.out, "@invariant ")?,
                Attribute::Interpolate(interpolation, sampling) => {
                    if sampling.is_some() && sampling != Some(crate::Sampling::Center) {
                        write!(
                            self.out,
                            "@interpolate({}, {}) ",
                            interpolation_str(
                                interpolation.unwrap_or(crate::Interpolation::Perspective)
                            ),
                            sampling_str(sampling.unwrap_or(crate::Sampling::Center))
                        )?;
                    } else if interpolation.is_some()
                        && interpolation != Some(crate::Interpolation::Perspective)
                    {
                        write!(
                            self.out,
                            "@interpolate({}) ",
                            interpolation_str(
                                interpolation.unwrap_or(crate::Interpolation::Perspective)
                            )
                        )?;
                    }
                }
            };
        }
        Ok(())
    }

    /// Helper method used to write structs
    ///
    /// # Notes
    /// Ends in a newline
    fn write_struct(
        &mut self,
        module: &Module,
        handle: Handle<crate::Type>,
        members: &[crate::StructMember],
    ) -> BackendResult {
        write!(self.out, "struct ")?;
        self.write_struct_name(module, handle)?;
        write!(self.out, " {{")?;
        writeln!(self.out)?;
        for (index, member) in members.iter().enumerate() {
            // The indentation is only for readability
            write!(self.out, "{}", back::INDENT)?;
            if let Some(ref binding) = member.binding {
                self.write_attributes(&map_binding_to_attribute(binding))?;
            }
            // Write struct member name and type
            let member_name = &self.names[&NameKey::StructMember(handle, index as u32)];
            write!(self.out, "{member_name}: ")?;
            self.write_type(module, member.ty)?;
            write!(self.out, ",")?;
            writeln!(self.out)?;
        }

        write!(self.out, "}}")?;

        writeln!(self.out)?;

        Ok(())
    }

    /// Helper method used to write non image/sampler types
    ///
    /// # Notes
    /// Adds no trailing or leading whitespace
    fn write_type(&mut self, module: &Module, ty: Handle<crate::Type>) -> BackendResult {
        let inner = &module.types[ty].inner;
        match *inner {
            TypeInner::Struct { .. } => self.write_struct_name(module, ty)?,
            ref other => self.write_value_type(module, other)?,
        }

        Ok(())
    }

    /// Helper method used to write value types
    ///
    /// # Notes
    /// Adds no trailing or leading whitespace
    fn write_value_type(&mut self, module: &Module, inner: &TypeInner) -> BackendResult {
        match *inner {
            TypeInner::Vector { size, scalar } => write!(
                self.out,
                "vec{}<{}>",
                back::vector_size_str(size),
                scalar_kind_str(scalar),
            )?,
            TypeInner::Sampler { comparison: false } => {
                write!(self.out, "sampler")?;
            }
            TypeInner::Sampler { comparison: true } => {
                write!(self.out, "sampler_comparison")?;
            }
            TypeInner::Image {
                dim,
                arrayed,
                class,
            } => {
                // More about texture types: https://gpuweb.github.io/gpuweb/wgsl/#sampled-texture-type
                use crate::ImageClass as Ic;

                let dim_str = image_dimension_str(dim);
                let arrayed_str = if arrayed { "_array" } else { "" };
                let (class_str, multisampled_str, format_str, storage_str) = match class {
                    Ic::Sampled { kind, multi } => (
                        "",
                        if multi { "multisampled_" } else { "" },
                        scalar_kind_str(crate::Scalar { kind, width: 4 }),
                        "",
                    ),
                    Ic::Depth { multi } => {
                        ("depth_", if multi { "multisampled_" } else { "" }, "", "")
                    }
                    Ic::Storage { format, access } => (
                        "storage_",
                        "",
                        storage_format_str(format),
                        if access.contains(crate::StorageAccess::LOAD | crate::StorageAccess::STORE)
                        {
                            ",read_write"
                        } else if access.contains(crate::StorageAccess::LOAD) {
                            ",read"
                        } else {
                            ",write"
                        },
                    ),
                };
                write!(
                    self.out,
                    "texture_{class_str}{multisampled_str}{dim_str}{arrayed_str}"
                )?;

                if !format_str.is_empty() {
                    write!(self.out, "<{format_str}{storage_str}>")?;
                }
            }
            TypeInner::Scalar(scalar) => {
                write!(self.out, "{}", scalar_kind_str(scalar))?;
            }
            TypeInner::Atomic(scalar) => {
                write!(self.out, "atomic<{}>", scalar_kind_str(scalar))?;
            }
            TypeInner::Array {
                base,
                size,
                stride: _,
            } => {
                // More info https://gpuweb.github.io/gpuweb/wgsl/#array-types
                // array<A, 3> -- Constant array
                // array<A> -- Dynamic array
                write!(self.out, "array<")?;
                match size {
                    crate::ArraySize::Constant(len) => {
                        self.write_type(module, base)?;
                        write!(self.out, ", {len}")?;
                    }
                    crate::ArraySize::Dynamic => {
                        self.write_type(module, base)?;
                    }
                }
                write!(self.out, ">")?;
            }
            TypeInner::BindingArray { base, size } => {
                // More info https://github.com/gpuweb/gpuweb/issues/2105
                write!(self.out, "binding_array<")?;
                match size {
                    crate::ArraySize::Constant(len) => {
                        self.write_type(module, base)?;
                        write!(self.out, ", {len}")?;
                    }
                    crate::ArraySize::Dynamic => {
                        self.write_type(module, base)?;
                    }
                }
                write!(self.out, ">")?;
            }
            TypeInner::Matrix {
                columns,
                rows,
                scalar,
            } => {
                write!(
                    self.out,
                    "mat{}x{}<{}>",
                    back::vector_size_str(columns),
                    back::vector_size_str(rows),
                    scalar_kind_str(scalar)
                )?;
            }
            TypeInner::Pointer { base, space } => {
                let (address, maybe_access) = address_space_str(space);
                // Everything but `AddressSpace::Handle` gives us a `address` name, but
                // Naga IR never produces pointers to handles, so it doesn't matter much
                // how we write such a type. Just write it as the base type alone.
                if let Some(space) = address {
                    write!(self.out, "ptr<{space}, ")?;
                }
                self.write_type(module, base)?;
                if address.is_some() {
                    if let Some(access) = maybe_access {
                        write!(self.out, ", {access}")?;
                    }
                    write!(self.out, ">")?;
                }
            }
            TypeInner::ValuePointer {
                size: None,
                scalar,
                space,
            } => {
                let (address, maybe_access) = address_space_str(space);
                if let Some(space) = address {
                    write!(self.out, "ptr<{}, {}", space, scalar_kind_str(scalar))?;
                    if let Some(access) = maybe_access {
                        write!(self.out, ", {access}")?;
                    }
                    write!(self.out, ">")?;
                } else {
                    return Err(Error::Unimplemented(format!(
                        "ValuePointer to AddressSpace::Handle {inner:?}"
                    )));
                }
            }
            TypeInner::ValuePointer {
                size: Some(size),
                scalar,
                space,
            } => {
                let (address, maybe_access) = address_space_str(space);
                if let Some(space) = address {
                    write!(
                        self.out,
                        "ptr<{}, vec{}<{}>",
                        space,
                        back::vector_size_str(size),
                        scalar_kind_str(scalar)
                    )?;
                    if let Some(access) = maybe_access {
                        write!(self.out, ", {access}")?;
                    }
                    write!(self.out, ">")?;
                } else {
                    return Err(Error::Unimplemented(format!(
                        "ValuePointer to AddressSpace::Handle {inner:?}"
                    )));
                }
                write!(self.out, ">")?;
            }
            TypeInner::AccelerationStructure => write!(self.out, "acceleration_structure")?,
            _ => {
                return Err(Error::Unimplemented(format!("write_value_type {inner:?}")));
            }
        }

        Ok(())
    }
    /// Helper method used to write statements
    ///
    /// # Notes
    /// Always adds a newline
    fn write_stmt(
        &mut self,
        module: &Module,
        stmt: &crate::Statement,
        func_ctx: &back::FunctionCtx<'_>,
        level: back::Level,
    ) -> BackendResult {
        use crate::{Expression, Statement};

        match *stmt {
            Statement::Emit(ref range) => {
                for handle in range.clone() {
                    let info = &func_ctx.info[handle];
                    let expr_name = if let Some(name) = func_ctx.named_expressions.get(&handle) {
                        // Front end provides names for all variables at the start of writing.
                        // But we write them to step by step. We need to recache them
                        // Otherwise, we could accidentally write variable name instead of full expression.
                        // Also, we use sanitized names! It defense backend from generating variable with name from reserved keywords.
                        Some(self.namer.call(name))
                    } else {
                        let expr = &func_ctx.expressions[handle];
                        let min_ref_count = expr.bake_ref_count();
                        // Forcefully creating baking expressions in some cases to help with readability
                        let required_baking_expr = match *expr {
                            Expression::ImageLoad { .. }
                            | Expression::ImageQuery { .. }
                            | Expression::ImageSample { .. } => true,
                            _ => false,
                        };
                        if min_ref_count <= info.ref_count || required_baking_expr {
                            Some(format!("{}{}", back::BAKE_PREFIX, handle.index()))
                        } else {
                            None
                        }
                    };

                    if let Some(name) = expr_name {
                        write!(self.out, "{level}")?;
                        self.start_named_expr(module, handle, func_ctx, &name)?;
                        self.write_expr(module, handle, func_ctx)?;
                        self.named_expressions.insert(handle, name);
                        writeln!(self.out, ";")?;
                    }
                }
            }
            // TODO: copy-paste from glsl-out
            Statement::If {
                condition,
                ref accept,
                ref reject,
            } => {
                write!(self.out, "{level}")?;
                write!(self.out, "if ")?;
                self.write_expr(module, condition, func_ctx)?;
                writeln!(self.out, " {{")?;

                let l2 = level.next();
                for sta in accept {
                    // Increase indentation to help with readability
                    self.write_stmt(module, sta, func_ctx, l2)?;
                }

                // If there are no statements in the reject block we skip writing it
                // This is only for readability
                if !reject.is_empty() {
                    writeln!(self.out, "{level}}} else {{")?;

                    for sta in reject {
                        // Increase indentation to help with readability
                        self.write_stmt(module, sta, func_ctx, l2)?;
                    }
                }

                writeln!(self.out, "{level}}}")?
            }
            Statement::Return { value } => {
                write!(self.out, "{level}")?;
                write!(self.out, "return")?;
                if let Some(return_value) = value {
                    // The leading space is important
                    write!(self.out, " ")?;
                    self.write_expr(module, return_value, func_ctx)?;
                }
                writeln!(self.out, ";")?;
            }
            // TODO: copy-paste from glsl-out
            Statement::Kill => {
                write!(self.out, "{level}")?;
                writeln!(self.out, "discard;")?
            }
            Statement::Store { pointer, value } => {
                write!(self.out, "{level}")?;

                let is_atomic_pointer = func_ctx
                    .resolve_type(pointer, &module.types)
                    .is_atomic_pointer(&module.types);

                if is_atomic_pointer {
                    write!(self.out, "atomicStore(")?;
                    self.write_expr(module, pointer, func_ctx)?;
                    write!(self.out, ", ")?;
                    self.write_expr(module, value, func_ctx)?;
                    write!(self.out, ")")?;
                } else {
                    self.write_expr_with_indirection(
                        module,
                        pointer,
                        func_ctx,
                        Indirection::Reference,
                    )?;
                    write!(self.out, " = ")?;
                    self.write_expr(module, value, func_ctx)?;
                }
                writeln!(self.out, ";")?
            }
            Statement::Call {
                function,
                ref arguments,
                result,
            } => {
                write!(self.out, "{level}")?;
                if let Some(expr) = result {
                    let name = format!("{}{}", back::BAKE_PREFIX, expr.index());
                    self.start_named_expr(module, expr, func_ctx, &name)?;
                    self.named_expressions.insert(expr, name);
                }
                let func_name = &self.names[&NameKey::Function(function)];
                write!(self.out, "{func_name}(")?;
                for (index, &argument) in arguments.iter().enumerate() {
                    if index != 0 {
                        write!(self.out, ", ")?;
                    }
                    self.write_expr(module, argument, func_ctx)?;
                }
                writeln!(self.out, ");")?
            }
            Statement::Atomic {
                pointer,
                ref fun,
                value,
                result,
            } => {
                write!(self.out, "{level}")?;
                let res_name = format!("{}{}", back::BAKE_PREFIX, result.index());
                self.start_named_expr(module, result, func_ctx, &res_name)?;
                self.named_expressions.insert(result, res_name);

                let fun_str = fun.to_wgsl();
                write!(self.out, "atomic{fun_str}(")?;
                self.write_expr(module, pointer, func_ctx)?;
                if let crate::AtomicFunction::Exchange { compare: Some(cmp) } = *fun {
                    write!(self.out, ", ")?;
                    self.write_expr(module, cmp, func_ctx)?;
                }
                write!(self.out, ", ")?;
                self.write_expr(module, value, func_ctx)?;
                writeln!(self.out, ");")?
            }
            Statement::WorkGroupUniformLoad { pointer, result } => {
                write!(self.out, "{level}")?;
                // TODO: Obey named expressions here.
                let res_name = format!("{}{}", back::BAKE_PREFIX, result.index());
                self.start_named_expr(module, result, func_ctx, &res_name)?;
                self.named_expressions.insert(result, res_name);
                write!(self.out, "workgroupUniformLoad(")?;
                self.write_expr(module, pointer, func_ctx)?;
                writeln!(self.out, ");")?;
            }
            Statement::ImageStore {
                image,
                coordinate,
                array_index,
                value,
            } => {
                write!(self.out, "{level}")?;
                write!(self.out, "textureStore(")?;
                self.write_expr(module, image, func_ctx)?;
                write!(self.out, ", ")?;
                self.write_expr(module, coordinate, func_ctx)?;
                if let Some(array_index_expr) = array_index {
                    write!(self.out, ", ")?;
                    self.write_expr(module, array_index_expr, func_ctx)?;
                }
                write!(self.out, ", ")?;
                self.write_expr(module, value, func_ctx)?;
                writeln!(self.out, ");")?;
            }
            // TODO: copy-paste from glsl-out
            Statement::Block(ref block) => {
                write!(self.out, "{level}")?;
                writeln!(self.out, "{{")?;
                for sta in block.iter() {
                    // Increase the indentation to help with readability
                    self.write_stmt(module, sta, func_ctx, level.next())?
                }
                writeln!(self.out, "{level}}}")?
            }
            Statement::Switch {
                selector,
                ref cases,
            } => {
                // Start the switch
                write!(self.out, "{level}")?;
                write!(self.out, "switch ")?;
                self.write_expr(module, selector, func_ctx)?;
                writeln!(self.out, " {{")?;

                let l2 = level.next();
                let mut new_case = true;
                for case in cases {
                    if case.fall_through && !case.body.is_empty() {
                        // TODO: we could do the same workaround as we did for the HLSL backend
                        return Err(Error::Unimplemented(
                            "fall-through switch case block".into(),
                        ));
                    }

                    match case.value {
                        crate::SwitchValue::I32(value) => {
                            if new_case {
                                write!(self.out, "{l2}case ")?;
                            }
                            write!(self.out, "{value}")?;
                        }
                        crate::SwitchValue::U32(value) => {
                            if new_case {
                                write!(self.out, "{l2}case ")?;
                            }
                            write!(self.out, "{value}u")?;
                        }
                        crate::SwitchValue::Default => {
                            if new_case {
                                if case.fall_through {
                                    write!(self.out, "{l2}case ")?;
                                } else {
                                    write!(self.out, "{l2}")?;
                                }
                            }
                            write!(self.out, "default")?;
                        }
                    }

                    new_case = !case.fall_through;

                    if case.fall_through {
                        write!(self.out, ", ")?;
                    } else {
                        writeln!(self.out, ": {{")?;
                    }

                    for sta in case.body.iter() {
                        self.write_stmt(module, sta, func_ctx, l2.next())?;
                    }

                    if !case.fall_through {
                        writeln!(self.out, "{l2}}}")?;
                    }
                }

                writeln!(self.out, "{level}}}")?
            }
            Statement::Loop {
                ref body,
                ref continuing,
                break_if,
            } => {
                write!(self.out, "{level}")?;
                writeln!(self.out, "loop {{")?;

                let l2 = level.next();
                for sta in body.iter() {
                    self.write_stmt(module, sta, func_ctx, l2)?;
                }

                // The continuing is optional so we don't need to write it if
                // it is empty, but the `break if` counts as a continuing statement
                // so even if `continuing` is empty we must generate it if a
                // `break if` exists
                if !continuing.is_empty() || break_if.is_some() {
                    writeln!(self.out, "{l2}continuing {{")?;
                    for sta in continuing.iter() {
                        self.write_stmt(module, sta, func_ctx, l2.next())?;
                    }

                    // The `break if` is always the last
                    // statement of the `continuing` block
                    if let Some(condition) = break_if {
                        // The trailing space is important
                        write!(self.out, "{}break if ", l2.next())?;
                        self.write_expr(module, condition, func_ctx)?;
                        // Close the `break if` statement
                        writeln!(self.out, ";")?;
                    }

                    writeln!(self.out, "{l2}}}")?;
                }

                writeln!(self.out, "{level}}}")?
            }
            Statement::Break => {
                writeln!(self.out, "{level}break;")?;
            }
            Statement::Continue => {
                writeln!(self.out, "{level}continue;")?;
            }
            Statement::Barrier(barrier) => {
                if barrier.contains(crate::Barrier::STORAGE) {
                    writeln!(self.out, "{level}storageBarrier();")?;
                }

                if barrier.contains(crate::Barrier::WORK_GROUP) {
                    writeln!(self.out, "{level}workgroupBarrier();")?;
                }

                if barrier.contains(crate::Barrier::SUB_GROUP) {
                    writeln!(self.out, "{level}subgroupBarrier();")?;
                }
            }
            Statement::RayQuery { .. } => unreachable!(),
            Statement::SubgroupBallot { result, predicate } => {
                write!(self.out, "{level}")?;
                let res_name = format!("{}{}", back::BAKE_PREFIX, result.index());
                self.start_named_expr(module, result, func_ctx, &res_name)?;
                self.named_expressions.insert(result, res_name);

                write!(self.out, "subgroupBallot(")?;
                if let Some(predicate) = predicate {
                    self.write_expr(module, predicate, func_ctx)?;
                }
                writeln!(self.out, ");")?;
            }
            Statement::SubgroupCollectiveOperation {
                op,
                collective_op,
                argument,
                result,
            } => {
                write!(self.out, "{level}")?;
                let res_name = format!("{}{}", back::BAKE_PREFIX, result.index());
                self.start_named_expr(module, result, func_ctx, &res_name)?;
                self.named_expressions.insert(result, res_name);

                match (collective_op, op) {
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::All) => {
                        write!(self.out, "subgroupAll(")?
                    }
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::Any) => {
                        write!(self.out, "subgroupAny(")?
                    }
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::Add) => {
                        write!(self.out, "subgroupAdd(")?
                    }
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::Mul) => {
                        write!(self.out, "subgroupMul(")?
                    }
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::Max) => {
                        write!(self.out, "subgroupMax(")?
                    }
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::Min) => {
                        write!(self.out, "subgroupMin(")?
                    }
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::And) => {
                        write!(self.out, "subgroupAnd(")?
                    }
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::Or) => {
                        write!(self.out, "subgroupOr(")?
                    }
                    (crate::CollectiveOperation::Reduce, crate::SubgroupOperation::Xor) => {
                        write!(self.out, "subgroupXor(")?
                    }
                    (crate::CollectiveOperation::ExclusiveScan, crate::SubgroupOperation::Add) => {
                        write!(self.out, "subgroupExclusiveAdd(")?
                    }
                    (crate::CollectiveOperation::ExclusiveScan, crate::SubgroupOperation::Mul) => {
                        write!(self.out, "subgroupExclusiveMul(")?
                    }
                    (crate::CollectiveOperation::InclusiveScan, crate::SubgroupOperation::Add) => {
                        write!(self.out, "subgroupInclusiveAdd(")?
                    }
                    (crate::CollectiveOperation::InclusiveScan, crate::SubgroupOperation::Mul) => {
                        write!(self.out, "subgroupInclusiveMul(")?
                    }
                    _ => unimplemented!(),
                }
                self.write_expr(module, argument, func_ctx)?;
                writeln!(self.out, ");")?;
            }
            Statement::SubgroupGather {
                mode,
                argument,
                result,
            } => {
                write!(self.out, "{level}")?;
                let res_name = format!("{}{}", back::BAKE_PREFIX, result.index());
                self.start_named_expr(module, result, func_ctx, &res_name)?;
                self.named_expressions.insert(result, res_name);

                match mode {
                    crate::GatherMode::BroadcastFirst => {
                        write!(self.out, "subgroupBroadcastFirst(")?;
                    }
                    crate::GatherMode::Broadcast(_) => {
                        write!(self.out, "subgroupBroadcast(")?;
                    }
                    crate::GatherMode::Shuffle(_) => {
                        write!(self.out, "subgroupShuffle(")?;
                    }
                    crate::GatherMode::ShuffleDown(_) => {
                        write!(self.out, "subgroupShuffleDown(")?;
                    }
                    crate::GatherMode::ShuffleUp(_) => {
                        write!(self.out, "subgroupShuffleUp(")?;
                    }
                    crate::GatherMode::ShuffleXor(_) => {
                        write!(self.out, "subgroupShuffleXor(")?;
                    }
                }
                self.write_expr(module, argument, func_ctx)?;
                match mode {
                    crate::GatherMode::BroadcastFirst => {}
                    crate::GatherMode::Broadcast(index)
                    | crate::GatherMode::Shuffle(index)
                    | crate::GatherMode::ShuffleDown(index)
                    | crate::GatherMode::ShuffleUp(index)
                    | crate::GatherMode::ShuffleXor(index) => {
                        write!(self.out, ", ")?;
                        self.write_expr(module, index, func_ctx)?;
                    }
                }
                writeln!(self.out, ");")?;
            }
        }

        Ok(())
    }

    /// Return the sort of indirection that `expr`'s plain form evaluates to.
    ///
    /// An expression's 'plain form' is the most general rendition of that
    /// expression into WGSL, lacking `&` or `*` operators:
    ///
    /// - The plain form of `LocalVariable(x)` is simply `x`, which is a reference
    ///   to the local variable's storage.
    ///
    /// - The plain form of `GlobalVariable(g)` is simply `g`, which is usually a
    ///   reference to the global variable's storage. However, globals in the
    ///   `Handle` address space are immutable, and `GlobalVariable` expressions for
    ///   those produce the value directly, not a pointer to it. Such
    ///   `GlobalVariable` expressions are `Ordinary`.
    ///
    /// - `Access` and `AccessIndex` are `Reference` when their `base` operand is a
    ///   pointer. If they are applied directly to a composite value, they are
    ///   `Ordinary`.
    ///
    /// Note that `FunctionArgument` expressions are never `Reference`, even when
    /// the argument's type is `Pointer`. `FunctionArgument` always evaluates to the
    /// argument's value directly, so any pointer it produces is merely the value
    /// passed by the caller.
    fn plain_form_indirection(
        &self,
        expr: Handle<crate::Expression>,
        module: &Module,
        func_ctx: &back::FunctionCtx<'_>,
    ) -> Indirection {
        use crate::Expression as Ex;

        // Named expressions are `let` expressions, which apply the Load Rule,
        // so if their type is a Naga pointer, then that must be a WGSL pointer
        // as well.
        if self.named_expressions.contains_key(&expr) {
            return Indirection::Ordinary;
        }

        match func_ctx.expressions[expr] {
            Ex::LocalVariable(_) => Indirection::Reference,
            Ex::GlobalVariable(handle) => {
                let global = &module.global_variables[handle];
                match global.space {
                    crate::AddressSpace::Handle => Indirection::Ordinary,
                    _ => Indirection::Reference,
                }
            }
            Ex::Access { base, .. } | Ex::AccessIndex { base, .. } => {
                let base_ty = func_ctx.resolve_type(base, &module.types);
                match *base_ty {
                    crate::TypeInner::Pointer { .. } | crate::TypeInner::ValuePointer { .. } => {
                        Indirection::Reference
                    }
                    _ => Indirection::Ordinary,
                }
            }
            _ => Indirection::Ordinary,
        }
    }

    fn start_named_expr(
        &mut self,
        module: &Module,
        handle: Handle<crate::Expression>,
        func_ctx: &back::FunctionCtx,
        name: &str,
    ) -> BackendResult {
        // Write variable name
        write!(self.out, "let {name}")?;
        if self.flags.contains(WriterFlags::EXPLICIT_TYPES) {
            write!(self.out, ": ")?;
            let ty = &func_ctx.info[handle].ty;
            // Write variable type
            match *ty {
                proc::TypeResolution::Handle(handle) => {
                    self.write_type(module, handle)?;
                }
                proc::TypeResolution::Value(ref inner) => {
                    self.write_value_type(module, inner)?;
                }
            }
        }

        write!(self.out, " = ")?;
        Ok(())
    }

    /// Write the ordinary WGSL form of `expr`.
    ///
    /// See `write_expr_with_indirection` for details.
    fn write_expr(
        &mut self,
        module: &Module,
        expr: Handle<crate::Expression>,
        func_ctx: &back::FunctionCtx<'_>,
    ) -> BackendResult {
        self.write_expr_with_indirection(module, expr, func_ctx, Indirection::Ordinary)
    }

    /// Write `expr` as a WGSL expression with the requested indirection.
    ///
    /// In terms of the WGSL grammar, the resulting expression is a
    /// `singular_expression`. It may be parenthesized. This makes it suitable
    /// for use as the operand of a unary or binary operator without worrying
    /// about precedence.
    ///
    /// This does not produce newlines or indentation.
    ///
    /// The `requested` argument indicates (roughly) whether Naga
    /// `Pointer`-valued expressions represent WGSL references or pointers. See
    /// `Indirection` for details.
    fn write_expr_with_indirection(
        &mut self,
        module: &Module,
        expr: Handle<crate::Expression>,
        func_ctx: &back::FunctionCtx<'_>,
        requested: Indirection,
    ) -> BackendResult {
        // If the plain form of the expression is not what we need, emit the
        // operator necessary to correct that.
        let plain = self.plain_form_indirection(expr, module, func_ctx);
        match (requested, plain) {
            (Indirection::Ordinary, Indirection::Reference) => {
                write!(self.out, "(&")?;
                self.write_expr_plain_form(module, expr, func_ctx, plain)?;
                write!(self.out, ")")?;
            }
            (Indirection::Reference, Indirection::Ordinary) => {
                write!(self.out, "(*")?;
                self.write_expr_plain_form(module, expr, func_ctx, plain)?;
                write!(self.out, ")")?;
            }
            (_, _) => self.write_expr_plain_form(module, expr, func_ctx, plain)?,
        }

        Ok(())
    }

    fn write_const_expression(
        &mut self,
        module: &Module,
        expr: Handle<crate::Expression>,
    ) -> BackendResult {
        self.write_possibly_const_expression(
            module,
            expr,
            &module.global_expressions,
            |writer, expr| writer.write_const_expression(module, expr),
        )
    }

    fn write_possibly_const_expression<E>(
        &mut self,
        module: &Module,
        expr: Handle<crate::Expression>,
        expressions: &crate::Arena<crate::Expression>,
        write_expression: E,
    ) -> BackendResult
    where
        E: Fn(&mut Self, Handle<crate::Expression>) -> BackendResult,
    {
        use crate::Expression;

        match expressions[expr] {
            Expression::Literal(literal) => match literal {
                crate::Literal::F32(value) => write!(self.out, "{}f", value)?,
                crate::Literal::U32(value) => write!(self.out, "{}u", value)?,
                crate::Literal::I32(value) => {
                    // `-2147483648i` is not valid WGSL. The most negative `i32`
                    // value can only be expressed in WGSL using AbstractInt and
                    // a unary negation operator.
                    if value == i32::MIN {
                        write!(self.out, "i32({})", value)?;
                    } else {
                        write!(self.out, "{}i", value)?;
                    }
                }
                crate::Literal::Bool(value) => write!(self.out, "{}", value)?,
                crate::Literal::F64(value) => write!(self.out, "{:?}lf", value)?,
                crate::Literal::I64(value) => {
                    // `-9223372036854775808li` is not valid WGSL. The most negative `i64`
                    // value can only be expressed in WGSL using AbstractInt and
                    // a unary negation operator.
                    if value == i64::MIN {
                        write!(self.out, "i64({})", value)?;
                    } else {
                        write!(self.out, "{}li", value)?;
                    }
                }
                crate::Literal::U64(value) => write!(self.out, "{:?}lu", value)?,
                crate::Literal::AbstractInt(_) | crate::Literal::AbstractFloat(_) => {
                    return Err(Error::Custom(
                        "Abstract types should not appear in IR presented to backends".into(),
                    ));
                }
            },
            Expression::Constant(handle) => {
                let constant = &module.constants[handle];
                if constant.name.is_some() {
                    write!(self.out, "{}", self.names[&NameKey::Constant(handle)])?;
                } else {
                    self.write_const_expression(module, constant.init)?;
                }
            }
            Expression::ZeroValue(ty) => {
                self.write_type(module, ty)?;
                write!(self.out, "()")?;
            }
            Expression::Compose { ty, ref components } => {
                self.write_type(module, ty)?;
                write!(self.out, "(")?;
                for (index, component) in components.iter().enumerate() {
                    if index != 0 {
                        write!(self.out, ", ")?;
                    }
                    write_expression(self, *component)?;
                }
                write!(self.out, ")")?
            }
            Expression::Splat { size, value } => {
                let size = back::vector_size_str(size);
                write!(self.out, "vec{size}(")?;
                write_expression(self, value)?;
                write!(self.out, ")")?;
            }
            _ => unreachable!(),
        }

        Ok(())
    }

    /// Write the 'plain form' of `expr`.
    ///
    /// An expression's 'plain form' is the most general rendition of that
    /// expression into WGSL, lacking `&` or `*` operators. The plain forms of
    /// `LocalVariable(x)` and `GlobalVariable(g)` are simply `x` and `g`. Such
    /// Naga expressions represent both WGSL pointers and references; it's the
    /// caller's responsibility to distinguish those cases appropriately.
    fn write_expr_plain_form(
        &mut self,
        module: &Module,
        expr: Handle<crate::Expression>,
        func_ctx: &back::FunctionCtx<'_>,
        indirection: Indirection,
    ) -> BackendResult {
        use crate::Expression;

        if let Some(name) = self.named_expressions.get(&expr) {
            write!(self.out, "{name}")?;
            return Ok(());
        }

        let expression = &func_ctx.expressions[expr];

        // Write the plain WGSL form of a Naga expression.
        //
        // The plain form of `LocalVariable` and `GlobalVariable` expressions is
        // simply the variable name; `*` and `&` operators are never emitted.
        //
        // The plain form of `Access` and `AccessIndex` expressions are WGSL
        // `postfix_expression` forms for member/component access and
        // subscripting.
        match *expression {
            Expression::Literal(_)
            | Expression::Constant(_)
            | Expression::ZeroValue(_)
            | Expression::Compose { .. }
            | Expression::Splat { .. } => {
                self.write_possibly_const_expression(
                    module,
                    expr,
                    func_ctx.expressions,
                    |writer, expr| writer.write_expr(module, expr, func_ctx),
                )?;
            }
            Expression::Override(_) => unreachable!(),
            Expression::FunctionArgument(pos) => {
                let name_key = func_ctx.argument_key(pos);
                let name = &self.names[&name_key];
                write!(self.out, "{name}")?;
            }
            Expression::Binary { op, left, right } => {
                write!(self.out, "(")?;
                self.write_expr(module, left, func_ctx)?;
                write!(self.out, " {} ", back::binary_operation_str(op))?;
                self.write_expr(module, right, func_ctx)?;
                write!(self.out, ")")?;
            }
            Expression::Access { base, index } => {
                self.write_expr_with_indirection(module, base, func_ctx, indirection)?;
                write!(self.out, "[")?;
                self.write_expr(module, index, func_ctx)?;
                write!(self.out, "]")?
            }
            Expression::AccessIndex { base, index } => {
                let base_ty_res = &func_ctx.info[base].ty;
                let mut resolved = base_ty_res.inner_with(&module.types);

                self.write_expr_with_indirection(module, base, func_ctx, indirection)?;

                let base_ty_handle = match *resolved {
                    TypeInner::Pointer { base, space: _ } => {
                        resolved = &module.types[base].inner;
                        Some(base)
                    }
                    _ => base_ty_res.handle(),
                };

                match *resolved {
                    TypeInner::Vector { .. } => {
                        // Write vector access as a swizzle
                        write!(self.out, ".{}", back::COMPONENTS[index as usize])?
                    }
                    TypeInner::Matrix { .. }
                    | TypeInner::Array { .. }
                    | TypeInner::BindingArray { .. }
                    | TypeInner::ValuePointer { .. } => write!(self.out, "[{index}]")?,
                    TypeInner::Struct { .. } => {
                        // This will never panic in case the type is a `Struct`, this is not true
                        // for other types so we can only check while inside this match arm
                        let ty = base_ty_handle.unwrap();

                        write!(
                            self.out,
                            ".{}",
                            &self.names[&NameKey::StructMember(ty, index)]
                        )?
                    }
                    ref other => return Err(Error::Custom(format!("Cannot index {other:?}"))),
                }
            }
            Expression::ImageSample {
                image,
                sampler,
                gather: None,
                coordinate,
                array_index,
                offset,
                level,
                depth_ref,
            } => {
                use crate::SampleLevel as Sl;

                let suffix_cmp = match depth_ref {
                    Some(_) => "Compare",
                    None => "",
                };
                let suffix_level = match level {
                    Sl::Auto => "",
                    Sl::Zero | Sl::Exact(_) => "Level",
                    Sl::Bias(_) => "Bias",
                    Sl::Gradient { .. } => "Grad",
                };

                write!(self.out, "textureSample{suffix_cmp}{suffix_level}(")?;
                self.write_expr(module, image, func_ctx)?;
                write!(self.out, ", ")?;
                self.write_expr(module, sampler, func_ctx)?;
                write!(self.out, ", ")?;
                self.write_expr(module, coordinate, func_ctx)?;

                if let Some(array_index) = array_index {
                    write!(self.out, ", ")?;
                    self.write_expr(module, array_index, func_ctx)?;
                }

                if let Some(depth_ref) = depth_ref {
                    write!(self.out, ", ")?;
                    self.write_expr(module, depth_ref, func_ctx)?;
                }

                match level {
                    Sl::Auto => {}
                    Sl::Zero => {
                        // Level 0 is implied for depth comparison
                        if depth_ref.is_none() {
                            write!(self.out, ", 0.0")?;
                        }
                    }
                    Sl::Exact(expr) => {
                        write!(self.out, ", ")?;
                        self.write_expr(module, expr, func_ctx)?;
                    }
                    Sl::Bias(expr) => {
                        write!(self.out, ", ")?;
                        self.write_expr(module, expr, func_ctx)?;
                    }
                    Sl::Gradient { x, y } => {
                        write!(self.out, ", ")?;
                        self.write_expr(module, x, func_ctx)?;
                        write!(self.out, ", ")?;
                        self.write_expr(module, y, func_ctx)?;
                    }
                }

                if let Some(offset) = offset {
                    write!(self.out, ", ")?;
                    self.write_const_expression(module, offset)?;
                }

                write!(self.out, ")")?;
            }

            Expression::ImageSample {
                image,
                sampler,
                gather: Some(component),
                coordinate,
                array_index,
                offset,
                level: _,
                depth_ref,
            } => {
                let suffix_cmp = match depth_ref {
                    Some(_) => "Compare",
                    None => "",
                };

                write!(self.out, "textureGather{suffix_cmp}(")?;
                match *func_ctx.resolve_type(image, &module.types) {
                    TypeInner::Image {
                        class: crate::ImageClass::Depth { multi: _ },
                        ..
                    } => {}
                    _ => {
                        write!(self.out, "{}, ", component as u8)?;
                    }
                }
                self.write_expr(module, image, func_ctx)?;
                write!(self.out, ", ")?;
                self.write_expr(module, sampler, func_ctx)?;
                write!(self.out, ", ")?;
                self.write_expr(module, coordinate, func_ctx)?;

                if let Some(array_index) = array_index {
                    write!(self.out, ", ")?;
                    self.write_expr(module, array_index, func_ctx)?;
                }

                if let Some(depth_ref) = depth_ref {
                    write!(self.out, ", ")?;
                    self.write_expr(module, depth_ref, func_ctx)?;
                }

                if let Some(offset) = offset {
                    write!(self.out, ", ")?;
                    self.write_const_expression(module, offset)?;
                }

                write!(self.out, ")")?;
            }
            Expression::ImageQuery { image, query } => {
                use crate::ImageQuery as Iq;

                let texture_function = match query {
                    Iq::Size { .. } => "textureDimensions",
                    Iq::NumLevels => "textureNumLevels",
                    Iq::NumLayers => "textureNumLayers",
                    Iq::NumSamples => "textureNumSamples",
                };

                write!(self.out, "{texture_function}(")?;
                self.write_expr(module, image, func_ctx)?;
                if let Iq::Size { level: Some(level) } = query {
                    write!(self.out, ", ")?;
                    self.write_expr(module, level, func_ctx)?;
                };
                write!(self.out, ")")?;
            }

            Expression::ImageLoad {
                image,
                coordinate,
                array_index,
                sample,
                level,
            } => {
                write!(self.out, "textureLoad(")?;
                self.write_expr(module, image, func_ctx)?;
                write!(self.out, ", ")?;
                self.write_expr(module, coordinate, func_ctx)?;
                if let Some(array_index) = array_index {
                    write!(self.out, ", ")?;
                    self.write_expr(module, array_index, func_ctx)?;
                }
                if let Some(index) = sample.or(level) {
                    write!(self.out, ", ")?;
                    self.write_expr(module, index, func_ctx)?;
                }
                write!(self.out, ")")?;
            }
            Expression::GlobalVariable(handle) => {
                let name = &self.names[&NameKey::GlobalVariable(handle)];
                write!(self.out, "{name}")?;
            }

            Expression::As {
                expr,
                kind,
                convert,
            } => {
                let inner = func_ctx.resolve_type(expr, &module.types);
                match *inner {
                    TypeInner::Matrix {
                        columns,
                        rows,
                        scalar,
                    } => {
                        let scalar = crate::Scalar {
                            kind,
                            width: convert.unwrap_or(scalar.width),
                        };
                        let scalar_kind_str = scalar_kind_str(scalar);
                        write!(
                            self.out,
                            "mat{}x{}<{}>",
                            back::vector_size_str(columns),
                            back::vector_size_str(rows),
                            scalar_kind_str
                        )?;
                    }
                    TypeInner::Vector {
                        size,
                        scalar: crate::Scalar { width, .. },
                    } => {
                        let scalar = crate::Scalar {
                            kind,
                            width: convert.unwrap_or(width),
                        };
                        let vector_size_str = back::vector_size_str(size);
                        let scalar_kind_str = scalar_kind_str(scalar);
                        if convert.is_some() {
                            write!(self.out, "vec{vector_size_str}<{scalar_kind_str}>")?;
                        } else {
                            write!(self.out, "bitcast<vec{vector_size_str}<{scalar_kind_str}>>")?;
                        }
                    }
                    TypeInner::Scalar(crate::Scalar { width, .. }) => {
                        let scalar = crate::Scalar {
                            kind,
                            width: convert.unwrap_or(width),
                        };
                        let scalar_kind_str = scalar_kind_str(scalar);
                        if convert.is_some() {
                            write!(self.out, "{scalar_kind_str}")?
                        } else {
                            write!(self.out, "bitcast<{scalar_kind_str}>")?
                        }
                    }
                    _ => {
                        return Err(Error::Unimplemented(format!(
                            "write_expr expression::as {inner:?}"
                        )));
                    }
                };
                write!(self.out, "(")?;
                self.write_expr(module, expr, func_ctx)?;
                write!(self.out, ")")?;
            }
            Expression::Load { pointer } => {
                let is_atomic_pointer = func_ctx
                    .resolve_type(pointer, &module.types)
                    .is_atomic_pointer(&module.types);

                if is_atomic_pointer {
                    write!(self.out, "atomicLoad(")?;
                    self.write_expr(module, pointer, func_ctx)?;
                    write!(self.out, ")")?;
                } else {
                    self.write_expr_with_indirection(
                        module,
                        pointer,
                        func_ctx,
                        Indirection::Reference,
                    )?;
                }
            }
            Expression::LocalVariable(handle) => {
                write!(self.out, "{}", self.names[&func_ctx.name_key(handle)])?
            }
            Expression::ArrayLength(expr) => {
                write!(self.out, "arrayLength(")?;
                self.write_expr(module, expr, func_ctx)?;
                write!(self.out, ")")?;
            }

            Expression::Math {
                fun,
                arg,
                arg1,
                arg2,
                arg3,
            } => {
                use crate::MathFunction as Mf;

                enum Function {
                    Regular(&'static str),
                }

                let function = match fun {
                    Mf::Abs => Function::Regular("abs"),
                    Mf::Min => Function::Regular("min"),
                    Mf::Max => Function::Regular("max"),
                    Mf::Clamp => Function::Regular("clamp"),
                    Mf::Saturate => Function::Regular("saturate"),
                    // trigonometry
                    Mf::Cos => Function::Regular("cos"),
                    Mf::Cosh => Function::Regular("cosh"),
                    Mf::Sin => Function::Regular("sin"),
                    Mf::Sinh => Function::Regular("sinh"),
                    Mf::Tan => Function::Regular("tan"),
                    Mf::Tanh => Function::Regular("tanh"),
                    Mf::Acos => Function::Regular("acos"),
                    Mf::Asin => Function::Regular("asin"),
                    Mf::Atan => Function::Regular("atan"),
                    Mf::Atan2 => Function::Regular("atan2"),
                    Mf::Asinh => Function::Regular("asinh"),
                    Mf::Acosh => Function::Regular("acosh"),
                    Mf::Atanh => Function::Regular("atanh"),
                    Mf::Radians => Function::Regular("radians"),
                    Mf::Degrees => Function::Regular("degrees"),
                    // decomposition
                    Mf::Ceil => Function::Regular("ceil"),
                    Mf::Floor => Function::Regular("floor"),
                    Mf::Round => Function::Regular("round"),
                    Mf::Fract => Function::Regular("fract"),
                    Mf::Trunc => Function::Regular("trunc"),
                    Mf::Modf => Function::Regular("modf"),
                    Mf::Frexp => Function::Regular("frexp"),
                    Mf::Ldexp => Function::Regular("ldexp"),
                    // exponent
                    Mf::Exp => Function::Regular("exp"),
                    Mf::Exp2 => Function::Regular("exp2"),
                    Mf::Log => Function::Regular("log"),
                    Mf::Log2 => Function::Regular("log2"),
                    Mf::Pow => Function::Regular("pow"),
                    // geometry
                    Mf::Dot => Function::Regular("dot"),
                    Mf::Cross => Function::Regular("cross"),
                    Mf::Distance => Function::Regular("distance"),
                    Mf::Length => Function::Regular("length"),
                    Mf::Normalize => Function::Regular("normalize"),
                    Mf::FaceForward => Function::Regular("faceForward"),
                    Mf::Reflect => Function::Regular("reflect"),
                    Mf::Refract => Function::Regular("refract"),
                    // computational
                    Mf::Sign => Function::Regular("sign"),
                    Mf::Fma => Function::Regular("fma"),
                    Mf::Mix => Function::Regular("mix"),
                    Mf::Step => Function::Regular("step"),
                    Mf::SmoothStep => Function::Regular("smoothstep"),
                    Mf::Sqrt => Function::Regular("sqrt"),
                    Mf::InverseSqrt => Function::Regular("inverseSqrt"),
                    Mf::Transpose => Function::Regular("transpose"),
                    Mf::Determinant => Function::Regular("determinant"),
                    // bits
                    Mf::CountTrailingZeros => Function::Regular("countTrailingZeros"),
                    Mf::CountLeadingZeros => Function::Regular("countLeadingZeros"),
                    Mf::CountOneBits => Function::Regular("countOneBits"),
                    Mf::ReverseBits => Function::Regular("reverseBits"),
                    Mf::ExtractBits => Function::Regular("extractBits"),
                    Mf::InsertBits => Function::Regular("insertBits"),
                    Mf::FindLsb => Function::Regular("firstTrailingBit"),
                    Mf::FindMsb => Function::Regular("firstLeadingBit"),
                    // data packing
                    Mf::Pack4x8snorm => Function::Regular("pack4x8snorm"),
                    Mf::Pack4x8unorm => Function::Regular("pack4x8unorm"),
                    Mf::Pack2x16snorm => Function::Regular("pack2x16snorm"),
                    Mf::Pack2x16unorm => Function::Regular("pack2x16unorm"),
                    Mf::Pack2x16float => Function::Regular("pack2x16float"),
                    // data unpacking
                    Mf::Unpack4x8snorm => Function::Regular("unpack4x8snorm"),
                    Mf::Unpack4x8unorm => Function::Regular("unpack4x8unorm"),
                    Mf::Unpack2x16snorm => Function::Regular("unpack2x16snorm"),
                    Mf::Unpack2x16unorm => Function::Regular("unpack2x16unorm"),
                    Mf::Unpack2x16float => Function::Regular("unpack2x16float"),
                    Mf::Inverse | Mf::Outer => {
                        return Err(Error::UnsupportedMathFunction(fun));
                    }
                };

                match function {
                    Function::Regular(fun_name) => {
                        write!(self.out, "{fun_name}(")?;
                        self.write_expr(module, arg, func_ctx)?;
                        for arg in IntoIterator::into_iter([arg1, arg2, arg3]).flatten() {
                            write!(self.out, ", ")?;
                            self.write_expr(module, arg, func_ctx)?;
                        }
                        write!(self.out, ")")?
                    }
                }
            }

            Expression::Swizzle {
                size,
                vector,
                pattern,
            } => {
                self.write_expr(module, vector, func_ctx)?;
                write!(self.out, ".")?;
                for &sc in pattern[..size as usize].iter() {
                    self.out.write_char(back::COMPONENTS[sc as usize])?;
                }
            }
            Expression::Unary { op, expr } => {
                let unary = match op {
                    crate::UnaryOperator::Negate => "-",
                    crate::UnaryOperator::LogicalNot => "!",
                    crate::UnaryOperator::BitwiseNot => "~",
                };

                write!(self.out, "{unary}(")?;
                self.write_expr(module, expr, func_ctx)?;

                write!(self.out, ")")?
            }

            Expression::Select {
                condition,
                accept,
                reject,
            } => {
                write!(self.out, "select(")?;
                self.write_expr(module, reject, func_ctx)?;
                write!(self.out, ", ")?;
                self.write_expr(module, accept, func_ctx)?;
                write!(self.out, ", ")?;
                self.write_expr(module, condition, func_ctx)?;
                write!(self.out, ")")?
            }
            Expression::Derivative { axis, ctrl, expr } => {
                use crate::{DerivativeAxis as Axis, DerivativeControl as Ctrl};
                let op = match (axis, ctrl) {
                    (Axis::X, Ctrl::Coarse) => "dpdxCoarse",
                    (Axis::X, Ctrl::Fine) => "dpdxFine",
                    (Axis::X, Ctrl::None) => "dpdx",
                    (Axis::Y, Ctrl::Coarse) => "dpdyCoarse",
                    (Axis::Y, Ctrl::Fine) => "dpdyFine",
                    (Axis::Y, Ctrl::None) => "dpdy",
                    (Axis::Width, Ctrl::Coarse) => "fwidthCoarse",
                    (Axis::Width, Ctrl::Fine) => "fwidthFine",
                    (Axis::Width, Ctrl::None) => "fwidth",
                };
                write!(self.out, "{op}(")?;
                self.write_expr(module, expr, func_ctx)?;
                write!(self.out, ")")?
            }
            Expression::Relational { fun, argument } => {
                use crate::RelationalFunction as Rf;

                let fun_name = match fun {
                    Rf::All => "all",
                    Rf::Any => "any",
                    _ => return Err(Error::UnsupportedRelationalFunction(fun)),
                };
                write!(self.out, "{fun_name}(")?;

                self.write_expr(module, argument, func_ctx)?;

                write!(self.out, ")")?
            }
            // Not supported yet
            Expression::RayQueryGetIntersection { .. } => unreachable!(),
            // Nothing to do here, since call expression already cached
            Expression::CallResult(_)
            | Expression::AtomicResult { .. }
            | Expression::RayQueryProceedResult
            | Expression::SubgroupBallotResult
            | Expression::SubgroupOperationResult { .. }
            | Expression::WorkGroupUniformLoadResult { .. } => {}
        }

        Ok(())
    }

    /// Helper method used to write global variables
    /// # Notes
    /// Always adds a newline
    fn write_global(
        &mut self,
        module: &Module,
        global: &crate::GlobalVariable,
        handle: Handle<crate::GlobalVariable>,
    ) -> BackendResult {
        // Write group and binding attributes if present
        if let Some(ref binding) = global.binding {
            self.write_attributes(&[
                Attribute::Group(binding.group),
                Attribute::Binding(binding.binding),
            ])?;
            writeln!(self.out)?;
        }

        // First write global name and address space if supported
        write!(self.out, "var")?;
        let (address, maybe_access) = address_space_str(global.space);
        if let Some(space) = address {
            write!(self.out, "<{space}")?;
            if let Some(access) = maybe_access {
                write!(self.out, ", {access}")?;
            }
            write!(self.out, ">")?;
        }
        write!(
            self.out,
            " {}: ",
            &self.names[&NameKey::GlobalVariable(handle)]
        )?;

        // Write global type
        self.write_type(module, global.ty)?;

        // Write initializer
        if let Some(init) = global.init {
            write!(self.out, " = ")?;
            self.write_const_expression(module, init)?;
        }

        // End with semicolon
        writeln!(self.out, ";")?;

        Ok(())
    }

    /// Helper method used to write global constants
    ///
    /// # Notes
    /// Ends in a newline
    fn write_global_constant(
        &mut self,
        module: &Module,
        handle: Handle<crate::Constant>,
    ) -> BackendResult {
        let name = &self.names[&NameKey::Constant(handle)];
        // First write only constant name
        write!(self.out, "const {name}: ")?;
        self.write_type(module, module.constants[handle].ty)?;
        write!(self.out, " = ")?;
        let init = module.constants[handle].init;
        self.write_const_expression(module, init)?;
        writeln!(self.out, ";")?;

        Ok(())
    }

    // See https://github.com/rust-lang/rust-clippy/issues/4979.
    #[allow(clippy::missing_const_for_fn)]
    pub fn finish(self) -> W {
        self.out
    }
}

fn builtin_str(built_in: crate::BuiltIn) -> Result<&'static str, Error> {
    use crate::BuiltIn as Bi;

    Ok(match built_in {
        Bi::VertexIndex => "vertex_index",
        Bi::InstanceIndex => "instance_index",
        Bi::Position { .. } => "position",
        Bi::FrontFacing => "front_facing",
        Bi::FragDepth => "frag_depth",
        Bi::LocalInvocationId => "local_invocation_id",
        Bi::LocalInvocationIndex => "local_invocation_index",
        Bi::GlobalInvocationId => "global_invocation_id",
        Bi::WorkGroupId => "workgroup_id",
        Bi::NumWorkGroups => "num_workgroups",
        Bi::SampleIndex => "sample_index",
        Bi::SampleMask => "sample_mask",
        Bi::PrimitiveIndex => "primitive_index",
        Bi::ViewIndex => "view_index",
        Bi::NumSubgroups => "num_subgroups",
        Bi::SubgroupId => "subgroup_id",
        Bi::SubgroupSize => "subgroup_size",
        Bi::SubgroupInvocationId => "subgroup_invocation_id",
        Bi::BaseInstance
        | Bi::BaseVertex
        | Bi::ClipDistance
        | Bi::CullDistance
        | Bi::PointSize
        | Bi::PointCoord
        | Bi::WorkGroupSize => {
            return Err(Error::Custom(format!("Unsupported builtin {built_in:?}")))
        }
    })
}

const fn image_dimension_str(dim: crate::ImageDimension) -> &'static str {
    use crate::ImageDimension as IDim;

    match dim {
        IDim::D1 => "1d",
        IDim::D2 => "2d",
        IDim::D3 => "3d",
        IDim::Cube => "cube",
    }
}

const fn scalar_kind_str(scalar: crate::Scalar) -> &'static str {
    use crate::Scalar;
    use crate::ScalarKind as Sk;

    match scalar {
        Scalar {
            kind: Sk::Float,
            width: 8,
        } => "f64",
        Scalar {
            kind: Sk::Float,
            width: 4,
        } => "f32",
        Scalar {
            kind: Sk::Sint,
            width: 4,
        } => "i32",
        Scalar {
            kind: Sk::Uint,
            width: 4,
        } => "u32",
        Scalar {
            kind: Sk::Sint,
            width: 8,
        } => "i64",
        Scalar {
            kind: Sk::Uint,
            width: 8,
        } => "u64",
        Scalar {
            kind: Sk::Bool,
            width: 1,
        } => "bool",
        _ => unreachable!(),
    }
}

const fn storage_format_str(format: crate::StorageFormat) -> &'static str {
    use crate::StorageFormat as Sf;

    match format {
        Sf::R8Unorm => "r8unorm",
        Sf::R8Snorm => "r8snorm",
        Sf::R8Uint => "r8uint",
        Sf::R8Sint => "r8sint",
        Sf::R16Uint => "r16uint",
        Sf::R16Sint => "r16sint",
        Sf::R16Float => "r16float",
        Sf::Rg8Unorm => "rg8unorm",
        Sf::Rg8Snorm => "rg8snorm",
        Sf::Rg8Uint => "rg8uint",
        Sf::Rg8Sint => "rg8sint",
        Sf::R32Uint => "r32uint",
        Sf::R32Sint => "r32sint",
        Sf::R32Float => "r32float",
        Sf::Rg16Uint => "rg16uint",
        Sf::Rg16Sint => "rg16sint",
        Sf::Rg16Float => "rg16float",
        Sf::Rgba8Unorm => "rgba8unorm",
        Sf::Rgba8Snorm => "rgba8snorm",
        Sf::Rgba8Uint => "rgba8uint",
        Sf::Rgba8Sint => "rgba8sint",
        Sf::Bgra8Unorm => "bgra8unorm",
        Sf::Rgb10a2Uint => "rgb10a2uint",
        Sf::Rgb10a2Unorm => "rgb10a2unorm",
        Sf::Rg11b10Float => "rg11b10float",
        Sf::Rg32Uint => "rg32uint",
        Sf::Rg32Sint => "rg32sint",
        Sf::Rg32Float => "rg32float",
        Sf::Rgba16Uint => "rgba16uint",
        Sf::Rgba16Sint => "rgba16sint",
        Sf::Rgba16Float => "rgba16float",
        Sf::Rgba32Uint => "rgba32uint",
        Sf::Rgba32Sint => "rgba32sint",
        Sf::Rgba32Float => "rgba32float",
        Sf::R16Unorm => "r16unorm",
        Sf::R16Snorm => "r16snorm",
        Sf::Rg16Unorm => "rg16unorm",
        Sf::Rg16Snorm => "rg16snorm",
        Sf::Rgba16Unorm => "rgba16unorm",
        Sf::Rgba16Snorm => "rgba16snorm",
    }
}

/// Helper function that returns the string corresponding to the WGSL interpolation qualifier
const fn interpolation_str(interpolation: crate::Interpolation) -> &'static str {
    use crate::Interpolation as I;

    match interpolation {
        I::Perspective => "perspective",
        I::Linear => "linear",
        I::Flat => "flat",
    }
}

/// Return the WGSL auxiliary qualifier for the given sampling value.
const fn sampling_str(sampling: crate::Sampling) -> &'static str {
    use crate::Sampling as S;

    match sampling {
        S::Center => "",
        S::Centroid => "centroid",
        S::Sample => "sample",
    }
}

const fn address_space_str(
    space: crate::AddressSpace,
) -> (Option<&'static str>, Option<&'static str>) {
    use crate::AddressSpace as As;

    (
        Some(match space {
            As::Private => "private",
            As::Uniform => "uniform",
            As::Storage { access } => {
                if access.contains(crate::StorageAccess::STORE) {
                    return (Some("storage"), Some("read_write"));
                } else {
                    "storage"
                }
            }
            As::PushConstant => "push_constant",
            As::WorkGroup => "workgroup",
            As::Handle => return (None, None),
            As::Function => "function",
        }),
        None,
    )
}

fn map_binding_to_attribute(binding: &crate::Binding) -> Vec<Attribute> {
    match *binding {
        crate::Binding::BuiltIn(built_in) => {
            if let crate::BuiltIn::Position { invariant: true } = built_in {
                vec![Attribute::BuiltIn(built_in), Attribute::Invariant]
            } else {
                vec![Attribute::BuiltIn(built_in)]
            }
        }
        crate::Binding::Location {
            location,
            interpolation,
            sampling,
            second_blend_source: false,
        } => vec![
            Attribute::Location(location),
            Attribute::Interpolate(interpolation, sampling),
        ],
        crate::Binding::Location {
            location,
            interpolation,
            sampling,
            second_blend_source: true,
        } => vec![
            Attribute::Location(location),
            Attribute::SecondBlendSource,
            Attribute::Interpolate(interpolation, sampling),
        ],
    }
}