go.types, types2: factor out isUntypedNumeric predicate

No need for Unalias or under calls for this predicate.

Change-Id: Idcdcda3e153d829ee5b26ad112ccfda3f4efedde
Reviewed-on: https://go-review.googlesource.com/c/go/+/581255
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Griesemer <gri@google.com>

2 files changed, 30 insertions, 14 deletions

diff --git a/src/cmd/compile/internal/types2/predicates.go b/src/cmd/compile/internal/types2/predicates.go
index 938f8dcf8b..6d9e6ec760 100644
--- a/src/cmd/compile/internal/types2/predicates.go
+++ b/src/cmd/compile/internal/types2/predicates.go
@@ -79,22 +79,30 @@ func isTypeLit(t Type) bool {
 }
 
 // isTyped reports whether t is typed; i.e., not an untyped
-// constant or boolean. isTyped may be called with types that
-// are not fully set up.
+// constant or boolean.
+// Safe to call from types that are not fully set up.
 func isTyped(t Type) bool {
-	// Alias or Named types cannot denote untyped types,
-	// thus we don't need to call Unalias or under
-	// (which would be unsafe to do for types that are
-	// not fully set up).
+	// Alias and named types cannot denote untyped types
+	// so there's no need to call Unalias or under, below.
 	b, _ := t.(*Basic)
 	return b == nil || b.info&IsUntyped == 0
 }
 
 // isUntyped(t) is the same as !isTyped(t).
+// Safe to call from types that are not fully set up.
 func isUntyped(t Type) bool {
 	return !isTyped(t)
 }
 
+// isUntypedNumeric reports whether t is an untyped numeric type.
+// Safe to call from types that are not fully set up.
+func isUntypedNumeric(t Type) bool {
+	// Alias and named types cannot denote untyped types
+	// so there's no need to call Unalias or under, below.
+	b, _ := t.(*Basic)
+	return b != nil && b.info&IsUntyped != 0 && b.info&IsNumeric != 0
+}
+
 // IsInterface reports whether t is an interface type.
 func IsInterface(t Type) bool {
 	_, ok := under(t).(*Interface)
@@ -539,7 +547,7 @@ func maxType(x, y Type) Type {
 	if x == y {
 		return x
 	}
-	if isUntyped(x) && isUntyped(y) && isNumeric(x) && isNumeric(y) {
+	if isUntypedNumeric(x) && isUntypedNumeric(y) {
 		// untyped types are basic types
 		if x.(*Basic).kind > y.(*Basic).kind {
 			return x
diff --git a/src/go/types/predicates.go b/src/go/types/predicates.go
index 07d07f9f12..1889694342 100644
--- a/src/go/types/predicates.go
+++ b/src/go/types/predicates.go
@@ -82,22 +82,30 @@ func isTypeLit(t Type) bool {
 }
 
 // isTyped reports whether t is typed; i.e., not an untyped
-// constant or boolean. isTyped may be called with types that
-// are not fully set up.
+// constant or boolean.
+// Safe to call from types that are not fully set up.
 func isTyped(t Type) bool {
-	// Alias or Named types cannot denote untyped types,
-	// thus we don't need to call Unalias or under
-	// (which would be unsafe to do for types that are
-	// not fully set up).
+	// Alias and named types cannot denote untyped types
+	// so there's no need to call Unalias or under, below.
 	b, _ := t.(*Basic)
 	return b == nil || b.info&IsUntyped == 0
 }
 
 // isUntyped(t) is the same as !isTyped(t).
+// Safe to call from types that are not fully set up.
 func isUntyped(t Type) bool {
 	return !isTyped(t)
 }
 
+// isUntypedNumeric reports whether t is an untyped numeric type.
+// Safe to call from types that are not fully set up.
+func isUntypedNumeric(t Type) bool {
+	// Alias and named types cannot denote untyped types
+	// so there's no need to call Unalias or under, below.
+	b, _ := t.(*Basic)
+	return b != nil && b.info&IsUntyped != 0 && b.info&IsNumeric != 0
+}
+
 // IsInterface reports whether t is an interface type.
 func IsInterface(t Type) bool {
 	_, ok := under(t).(*Interface)
@@ -542,7 +550,7 @@ func maxType(x, y Type) Type {
 	if x == y {
 		return x
 	}
-	if isUntyped(x) && isUntyped(y) && isNumeric(x) && isNumeric(y) {
+	if isUntypedNumeric(x) && isUntypedNumeric(y) {
 		// untyped types are basic types
 		if x.(*Basic).kind > y.(*Basic).kind {
 			return x