go/types: skip tests that require GOROOT/test if it is not present

cmd/distpack removes GOROOT/test from its archive of the distribution.

For #24904.

Change-Id: Ifde441f048f8af52f8973555b196ab0520b48ab7
Reviewed-on: https://go-review.googlesource.com/c/go/+/504057
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>

Author: Bryan C. Mills

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

@@ -206,6 +206,14 @@ func firstComment(filename string) (first string) {
 func testTestDir(t *testing.T, path string, ignore ...string) {
 	files, err := os.ReadDir(path)
 	if err != nil {
+		// cmd/distpack deletes GOROOT/test, so skip the test if it isn't present.
+		// cmd/distpack also requires GOROOT/VERSION to exist, so use that to
+		// suppress false-positive skips.
+		if _, err := os.Stat(filepath.Join(testenv.GOROOT(t), "test")); os.IsNotExist(err) {
+			if _, err := os.Stat(filepath.Join(testenv.GOROOT(t), "VERSION")); err == nil {
+				t.Skipf("skipping: GOROOT/test not present")
+			}
+		}
 		t.Fatal(err)
 	}
 

src/go/types/stdlib_test.go

@@ -209,6 +209,14 @@ func firstComment(filename string) string {
 func testTestDir(t *testing.T, path string, ignore ...string) {
 	files, err := os.ReadDir(path)
 	if err != nil {
+		// cmd/distpack deletes GOROOT/test, so skip the test if it isn't present.
+		// cmd/distpack also requires GOROOT/VERSION to exist, so use that to
+		// suppress false-positive skips.
+		if _, err := os.Stat(filepath.Join(testenv.GOROOT(t), "test")); os.IsNotExist(err) {
+			if _, err := os.Stat(filepath.Join(testenv.GOROOT(t), "VERSION")); err == nil {
+				t.Skipf("skipping: GOROOT/test not present")
+			}
+		}
 		t.Fatal(err)
 	}