tools/intrinsic: Fix validation for type matchers

The tooling does not expect, nor can handel a type matcher to be used as a parameter or a direct template parameter to another type. Make this an error.

Change-Id: I28c04c00c7fa1cb5130c53215a90a59d660d6fa3
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/114380
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

tools/src/tint/intrinsic/resolver/resolve.go

@@ -352,7 +352,7 @@ func (r *resolver) intrinsic(
 			case ast.Builtin, ast.Operator:
 				overload.ConstEvalFunction = overload.Decl.Name
 			case ast.Initializer:
-				overload.ConstEvalFunction = "init"
+				overload.ConstEvalFunction = "Init"
 			case ast.Converter:
 				overload.ConstEvalFunction = "Conv"
 			}
@@ -448,12 +448,15 @@ func (r *resolver) intrinsic(
 }
 
 // fullyQualifiedName() resolves the ast.TemplatedName to a sem.FullyQualifiedName.
+// The resolved name cannot be a TypeMatcher
 func (r *resolver) fullyQualifiedName(s *scope, arg ast.TemplatedName) (sem.FullyQualifiedName, error) {
 	target, err := r.lookupNamed(s, arg)
 	if err != nil {
 		return sem.FullyQualifiedName{}, err
 	}
-
+	if _, ok := target.(*sem.TypeMatcher); ok {
+		return sem.FullyQualifiedName{}, fmt.Errorf("%v type matcher cannot be used directly here. Use a matcher constrained template argument", arg.Source)
+	}
 	fqn := sem.FullyQualifiedName{
 		Target:            target,
 		TemplateArguments: make([]interface{}, len(arg.TemplateArgs)),

tools/src/tint/intrinsic/resolver/resolver_test.go

@@ -86,13 +86,6 @@ fn f<T: m>(P<T>) -> T`,
 			success,
 		}, {
 			`
-type f32
-type P<T>
-match m: f32
-fn f(P<m>)`,
-			success,
-		}, {
-			`
 enum e { a }
 match m: e.a
 fn f(m)`,
@@ -511,6 +504,20 @@ enum E { a b }
 match m: E.a | E.b
 conv F<M: m>(P<M>)`,
 			`file.txt:4:16 cannot use template enum 'E' as template number`,
+		}, {
+			`
+type f32
+type P<T>
+match m: f32
+fn f(m)`,
+			`file.txt:4:6 type matcher cannot be used directly here. Use a matcher constrained template argument`,
+		}, {
+			`
+type f32
+type P<T>
+match m: f32
+fn f(P<m>)`,
+			`file.txt:4:8 type matcher cannot be used directly here. Use a matcher constrained template argument`,
 		},
 	} {