go/types, types2: always accept type parameters when running Manual test

This makes it easier to run tests on existing generic code that is
not using the `.go2` ending currently used by type checker tests.

For #49074.

Change-Id: I1501463c55dbe1d709918786e1a43b6d1bf1629a
Reviewed-on: https://go-review.googlesource.com/c/go/+/357050
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/src/cmd/compile/internal/types2/check_test.go b/src/cmd/compile/internal/types2/check_test.go
index bc68e76..e71df87 100644
--- a/src/cmd/compile/internal/types2/check_test.go
+++ b/src/cmd/compile/internal/types2/check_test.go
@@ -99,7 +99,7 @@
 	}
 
 	var mode syntax.Mode
-	if strings.HasSuffix(filenames[0], ".go2") {
+	if strings.HasSuffix(filenames[0], ".go2") || manual {
 		mode |= syntax.AllowGenerics
 	}
 	// parse files and collect parser errors
diff --git a/src/go/types/check_test.go b/src/go/types/check_test.go
index e9df90c..e617673 100644
--- a/src/go/types/check_test.go
+++ b/src/go/types/check_test.go
@@ -210,7 +210,7 @@
 	}
 
 	mode := parser.AllErrors
-	if !strings.HasSuffix(filenames[0], ".go2") {
+	if !strings.HasSuffix(filenames[0], ".go2") && !manual {
 		mode |= typeparams.DisallowParsing
 	}