diag(naga): add def. article and noun qual. to DirectiveNotYetImplemented

naga/src/front/wgsl/error.rs

@@ -916,7 +916,7 @@ impl<'a> Error<'a> {
             },
             Error::DirectiveNotYetImplemented { kind, span } => ParseError {
                 message: format!(
-                    "`{}` is not yet implemented",
+                    "the `{}` directive is not yet implemented",
                     DirectiveKind::Unimplemented(kind).to_ident()
                 ),
                 labels: vec![(

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

@@ -81,7 +81,7 @@ mod test {
                 UnimplementedDirectiveKind::Diagnostic => {
                     shader = "diagnostic(off,derivative_uniformity);";
                     expected_msg = "\
-error: `diagnostic` is not yet implemented
+error: the `diagnostic` directive is not yet implemented
   ┌─ wgsl:1:1
   │
 1 │ diagnostic(off,derivative_uniformity);