[naga] Error on duplicate fields in structs (gfx-rs#7088)

* error in wgsl-in

* changelog

* add test

Author: SparkyPotato

CHANGELOG.md

@@ -83,6 +83,7 @@ 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).
 
 #### General
 

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

@@ -12,7 +12,7 @@ use crate::front::wgsl::parse::lexer::{Lexer, Token};
 use crate::front::wgsl::parse::number::Number;
 use crate::front::wgsl::Scalar;
 use crate::front::SymbolTable;
-use crate::{Arena, FastIndexSet, Handle, ShaderStage, Span};
+use crate::{Arena, FastHashSet, FastIndexSet, Handle, ShaderStage, Span};
 
 pub mod ast;
 pub mod conv;
@@ -1171,6 +1171,7 @@ impl Parser {
         ctx: &mut ExpressionContext<'a, '_, '_>,
     ) -> Result<Vec<ast::StructMember<'a>>, Error<'a>> {
         let mut members = Vec::new();
+        let mut member_names = FastHashSet::default();
 
         lexer.expect(Token::Paren('{'))?;
         let mut ready = true;
@@ -1217,6 +1218,17 @@ impl Parser {
                 size: size.value,
                 align: align.value,
             });
+
+            if !member_names.insert(name.name) {
+                return Err(Error::Redefinition {
+                    previous: members
+                        .iter()
+                        .find(|x| x.name.name == name.name)
+                        .map(|x| x.name.span)
+                        .unwrap(),
+                    current: name.span,
+                });
+            }
         }
 
         Ok(members)

naga/tests/wgsl_errors.rs

@@ -2092,6 +2092,27 @@ fn function_param_redefinition_as_local() {
     )
 }
 
+#[test]
+fn struct_member_redefinition() {
+    check(
+        "
+        struct A {
+            a: f32,
+            a: f32,
+        }
+    ",
+        r###"error: redefinition of `a`
+  ┌─ wgsl:3:13
+  │
+3 │             a: f32,
+  │             ^ previous definition of `a`
+4 │             a: f32,
+  │             ^ redefinition of `a`
+
+"###,
+    )
+}
+
 #[test]
 fn function_must_return_value() {
     check_validation!(