go/types, types2: remove another coreType call in type checking range clause

For #70128.

Change-Id: I5949bccbfaaebc435ae8ac7c70580d9740de6f00
Reviewed-on: https://go-review.googlesource.com/c/go/+/652136
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
Auto-Submit: Robert Griesemer <[email protected]>

Author: griesemer

src/cmd/compile/internal/types2/stmt.go

@@ -1040,10 +1040,15 @@ func rangeKeyVal(check *Checker, orig Type, allowVersion func(goVersion) bool) (
 		}
 		assert(typ.Recv() == nil)
 		// check iterator argument type
-		cb, _ := coreType(typ.Params().At(0).Type()).(*Signature)
+		var cause2 string
+		cb, _ := sharedUnder(check, typ.Params().At(0).Type(), &cause2).(*Signature)
 		switch {
 		case cb == nil:
-			return bad("func must be func(yield func(...) bool): argument is not func")
+			if cause2 != "" {
+				return bad(check.sprintf("func must be func(yield func(...) bool): in yield type, %s", cause2))
+			} else {
+				return bad("func must be func(yield func(...) bool): argument is not func")
+			}
 		case cb.Params().Len() > 2:
 			return bad("func must be func(yield func(...) bool): yield func has too many parameters")
 		case cb.Results().Len() != 1 || !Identical(cb.Results().At(0).Type(), universeBool):

src/go/types/stmt.go

@@ -1058,10 +1058,15 @@ func rangeKeyVal(check *Checker, orig Type, allowVersion func(goVersion) bool) (
 		}
 		assert(typ.Recv() == nil)
 		// check iterator argument type
-		cb, _ := coreType(typ.Params().At(0).Type()).(*Signature)
+		var cause2 string
+		cb, _ := sharedUnder(check, typ.Params().At(0).Type(), &cause2).(*Signature)
 		switch {
 		case cb == nil:
-			return bad("func must be func(yield func(...) bool): argument is not func")
+			if cause2 != "" {
+				return bad(check.sprintf("func must be func(yield func(...) bool): in yield type, %s", cause2))
+			} else {
+				return bad("func must be func(yield func(...) bool): argument is not func")
+			}
 		case cb.Params().Len() > 2:
 			return bad("func must be func(yield func(...) bool): yield func has too many parameters")
 		case cb.Results().Len() != 1 || !Identical(cb.Results().At(0).Type(), universeBool):

src/internal/types/testdata/spec/range.go

@@ -164,6 +164,11 @@ func _[T ~func(func(int) bool)](x T) {
 	}
 }
 
+func _[T func() bool | func(int) bool]() {
+	for range func /* ERROR "func must be func(yield func(...) bool): in yield type, func() bool and func(int) bool have different underlying types" */ (T) {} {
+	}
+}
+
 // go.dev/issue/65236
 
 func seq0(func() bool) {}