go/types, types2: consolidate a test file with different syntax errors

For #54511.

Change-Id: I317c5f9beed7f1de4979ec12c6ec8d5de71bac1c
Reviewed-on: https://go-review.googlesource.com/c/go/+/426554
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>

src/cmd/compile/internal/types2/testdata/fixedbugs/issue51658.go

@@ -2,21 +2,25 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// This test checks syntax errors which differ between
+// go/parser and the syntax package.
+// TODO: consolidate eventually
+
 package p
 
-type F { // ERROR syntax error
+type F { // ERROR expected type|type declaration
 	float64
-} // ERROR syntax error
+} // ERROR expected declaration|non-declaration statement
 
 func _[T F | int](x T) {
 	_ = x == 0 // don't crash when recording type of 0
 }
 
 // test case from issue
 
-type FloatType { // ERROR syntax error
+type FloatType { // ERROR expected type|type declaration
 	float32 | float64
-} // ERROR syntax error
+} // ERROR expected declaration|non-declaration statement
 
 type IntegerType interface {
 	int8 | int16 | int32 | int64 | int |

src/go/types/testdata/fixedbugs/issue51658.go

@@ -2,21 +2,25 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// This test checks syntax errors which differ between
+// go/parser and the syntax package.
+// TODO: consolidate eventually
+
 package p
 
-type F { // ERROR expected type
+type F { // ERROR expected type|type declaration
 	float64
-} // ERROR expected declaration
+} // ERROR expected declaration|non-declaration statement
 
 func _[T F | int](x T) {
 	_ = x == 0 // don't crash when recording type of 0
 }
 
 // test case from issue
 
-type FloatType { // ERROR expected type
+type FloatType { // ERROR expected type|type declaration
 	float32 | float64
-} // ERROR expected declaration
+} // ERROR expected declaration|non-declaration statement
 
 type IntegerType interface {
 	int8 | int16 | int32 | int64 | int |