[naga] allow trailing commas in template lists

CHANGELOG.md

@@ -98,6 +98,7 @@ By @brodycj in [#6924](https://github.com/gfx-rs/wgpu/pull/6924).
 - Fix some instances of functions which have a return type but don't return a value being incorrectly validated. By @jamienicol in [#7013](https://github.com/gfx-rs/wgpu/pull/7013).
 - Allow abstract expressions to be used in WGSL function return statements. By @jamienicol in [#7035](https://github.com/gfx-rs/wgpu/pull/7035).
 - Error if structs have two fields with the same name. By @SparkyPotato in [#7088](https://github.com/gfx-rs/wgpu/pull/7088).
+- Allow template lists to have a trailing comma. By @KentSlaney in [#7142](https://github.com/gfx-rs/wgpu/pull/7142).
 
 #### General
 

naga/src/front/wgsl/parse/lexer.rs

@@ -352,6 +352,10 @@ impl<'a> Lexer<'a> {
         }
     }
 
+    pub(in crate::front::wgsl) fn optional_generic_term(&mut self) -> bool {
+        self.skip(Token::Separator(',')) && self.peek().0 != Token::Paren('>')
+    }
+
     /// If the next token matches it is skipped and true is returned
     pub(in crate::front::wgsl) fn skip(&mut self, what: Token<'_>) -> bool {
         let (peeked_token, rest) = self.peek_token_and_rest();

naga/src/front/wgsl/parse/mod.rs

@@ -576,8 +576,9 @@ impl Parser {
             (Token::Paren('<'), ast::ConstructorType::PartialArray) => {
                 lexer.expect_generic_paren('<')?;
                 let base = self.type_decl(lexer, ctx)?;
-                let size = if lexer.skip(Token::Separator(',')) {
+                let size = if lexer.optional_generic_term() {
                     let expr = self.const_generic_expression(lexer, ctx)?;
+                    lexer.skip(Token::Separator(','));
                     ast::ArraySize::Constant(expr)
                 } else {
                     ast::ArraySize::Dynamic
@@ -1244,6 +1245,7 @@ impl Parser {
         let start = lexer.start_byte_offset();
         let ty = self.type_decl(lexer, ctx)?;
         let span = lexer.span_from(start);
+        lexer.skip(Token::Separator(','));
         lexer.expect_generic_paren('>')?;
         Ok((ty, span))
     }
@@ -1436,8 +1438,10 @@ impl Parser {
                 lexer.expect(Token::Separator(','))?;
                 let base = self.type_decl(lexer, ctx)?;
                 if let crate::AddressSpace::Storage { ref mut access } = space {
-                    *access = if lexer.skip(Token::Separator(',')) {
-                        lexer.next_storage_access()?
+                    *access = if lexer.optional_generic_term() {
+                        let result = lexer.next_storage_access()?;
+                        lexer.skip(Token::Separator(','));
+                        result
                     } else {
                         crate::StorageAccess::LOAD
                     };
@@ -1448,8 +1452,9 @@ impl Parser {
             "array" => {
                 lexer.expect_generic_paren('<')?;
                 let base = self.type_decl(lexer, ctx)?;
-                let size = if lexer.skip(Token::Separator(',')) {
+                let size = if lexer.optional_generic_term() {
                     let size = self.const_generic_expression(lexer, ctx)?;
+                    lexer.skip(Token::Separator(','));
                     ast::ArraySize::Constant(size)
                 } else {
                     ast::ArraySize::Dynamic
@@ -1461,8 +1466,9 @@ impl Parser {
             "binding_array" => {
                 lexer.expect_generic_paren('<')?;
                 let base = self.type_decl(lexer, ctx)?;
-                let size = if lexer.skip(Token::Separator(',')) {
+                let size = if lexer.optional_generic_term() {
                     let size = self.unary_expression(lexer, ctx)?;
+                    lexer.skip(Token::Separator(','));
                     ast::ArraySize::Constant(size)
                 } else {
                     ast::ArraySize::Dynamic

tests/tests/shader/array_size_overrides.rs

@@ -6,10 +6,10 @@ use wgpu_test::{fail_if, gpu_test, GpuTestConfiguration, TestParameters, Testing
 const SHADER: &str = r#"
     override n = 8;
 
-    var<workgroup> arr: array<u32, n - 2>;
+    var<workgroup> arr: array<u32, n - 2,>;
 
     @group(0) @binding(0)
-    var<storage, read_write> output: array<u32>;
+    var<storage, read_write> output: array<u32,>;
 
     @compute @workgroup_size(1) fn main() {
         // 1d spiral