go/types: match types2 error for invalid map key

Use "invalid" rather than "incomparable" in error message for map key
types that are not comparable. This is the original compiler error
message and many tests check for this specific message. The type
checker does provide an additional explanation if the reason for
the error is not obvious (e.g. for type parameters).

For #54511.

Change-Id: Idb76c48b4dfbfd66a7deac728a552e07f14e06d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/424905
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>

src/go/types/testdata/check/cycles0.go

@@ -66,7 +66,7 @@ type (
 	I6 interface{ I5 }
 
 	// maps
-	M0 map[M0 /* ERROR incomparable map key */ ]M0
+	M0 map[M0 /* ERROR invalid map key */ ]M0
 
 	// channels
 	C0 chan C0
@@ -115,7 +115,7 @@ func _() {
 		i0 /* ERROR cycle */ interface{ i0 }
 
 		// maps
-		m0 map[m0 /* ERROR incomparable map key */ ]m0
+		m0 map[m0 /* ERROR invalid map key */ ]m0
 
 		// channels
 		c0 chan c0
@@ -124,10 +124,10 @@ func _() {
 
 // test cases for issue 6667
 
-type A [10]map[A /* ERROR incomparable map key */ ]bool
+type A [10]map[A /* ERROR invalid map key */ ]bool
 
 type S struct {
-	m map[S /* ERROR incomparable map key */ ]bool
+	m map[S /* ERROR invalid map key */ ]bool
 }
 
 // test cases for issue 7236

src/go/types/testdata/check/typeparams.go

@@ -75,7 +75,7 @@ func new[T any]() *T {
 var _ = new /* ERROR cannot use generic function new */
 var _ *int = new[int]()
 
-func _[T any](map[T /* ERROR incomparable map key type T \(missing comparable constraint\) */]int) {} // w/o constraint we don't know if T is comparable
+func _[T any](map[T /* ERROR invalid map key type T \(missing comparable constraint\) */]int) {} // w/o constraint we don't know if T is comparable
 
 func f1[T1 any](struct{T1 /* ERROR cannot be a .* type parameter */ }) int { panic(0) }
 var _ = f1[int](struct{T1}{})

src/go/types/typexpr.go

@@ -348,7 +348,7 @@ func (check *Checker) typInternal(e0 ast.Expr, def *Named) (T Type) {
 				if isTypeParam(typ.key) {
 					why = " (missing comparable constraint)"
 				}
-				check.errorf(e.Key, _IncomparableMapKey, "incomparable map key type %s%s", typ.key, why)
+				check.errorf(e.Key, _IncomparableMapKey, "invalid map key type %s%s", typ.key, why)
 			}
 		}).describef(e.Key, "check map key %s", typ.key)