Detect a common syntax error case for diagnostic_directive

CHANGELOG.md

@@ -131,6 +131,7 @@ By @ErichDonGubler in [#6456](https://github.com/gfx-rs/wgpu/pull/6456), [#6148]
 
 - Show types of LHS and RHS in binary operation type mismatch errors. By @ErichDonGubler in [#6450](https://github.com/gfx-rs/wgpu/pull/6450).
 - The GLSL parser now uses less expressions for function calls. By @magcius in [#6604](https://github.com/gfx-rs/wgpu/pull/6604).
+- Add a note to help with a common syntax error case for global diagnostic filter directives. By @e-hat in [#6718](https://github.com/gfx-rs/wgpu/pull/6718)
 
 #### General
 

naga/src/front/wgsl/error.rs

@@ -304,6 +304,7 @@ pub(crate) enum Error<'a> {
     },
     DiagnosticAttributeNotSupported {
         on_what_plural: &'static str,
+        intended_diagnostic_directive: bool,
         spans: Vec<Span>,
     },
 }
@@ -1082,6 +1083,7 @@ impl<'a> Error<'a> {
             },
             Error::DiagnosticAttributeNotSupported {
                 on_what_plural,
+                intended_diagnostic_directive,
                 ref spans,
             } => ParseError {
                 message: format!(
@@ -1098,7 +1100,15 @@ impl<'a> Error<'a> {
                         "some statements, and `switch`/`loop` bodies."
                     )
                     .into(),
-                    "These attributes are well-formed, you likely just need to move them.".into(),
+                    {
+                        if intended_diagnostic_directive {
+                            concat!("To declare a diagnostic filter that applies to the entire module, ", 
+                            "move this line to the top of the file and remove the `@` symbol.").into()
+                        } else {
+                            "These attributes are well-formed, you likely just need to move them."
+                                .into()
+                        }
+                    },
                 ],
             },
         }

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

@@ -2472,6 +2472,9 @@ impl Parser {
                 } else {
                     Err(Error::DiagnosticAttributeNotSupported {
                         on_what_plural,
+                        // In this case the user may have intended to create a global diagnostic filter directive,
+                        // so display a note to them suggesting the correct syntax.
+                        intended_diagnostic_directive: on_what_plural == "semicolons",
                         spans: filters.spans().collect(),
                     })
                 }

naga/src/front/wgsl/tests.rs

@@ -797,4 +797,26 @@ error: found conflicting `diagnostic(…)` rule(s)
 ");
         }
     }
+
+    use crate::front::wgsl::assert_parse_err;
+    #[test]
+    fn intended_global_directive() {
+        let shader = "
+@diagnostic(off, my.lint);
+";
+        assert_parse_err(
+            shader,
+            "\
+error: `@diagnostic(…)` attribute(s) on semicolons are not supported
+  ┌─ wgsl:2:1
+  │
+2 │ @diagnostic(off, my.lint);
+  │ ^^^^^^^^^^^^^^^^^^^^^^^^^
+  │
+  = note: `@diagnostic(…)` attributes are only permitted on `fn`s, some statements, and `switch`/`loop` bodies.
+  = note: To declare a diagnostic filter that applies to the entire module, move this line to the top of the file and remove the `@` symbol.
+
+"
+        );
+    }
 }