go/types, types2: better error message for invalid ERROR pattern in tests

When unquoting of an ERROR or ERRORx pattern fails, say so instead of
simply printing "syntax error".

Change-Id: I586dffa86ca80f5b40a5cbe16a7005cc1f7862f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/586958
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Auto-Submit: Robert Griesemer <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: griesemer

Diff for: src/cmd/compile/internal/types2/check_test.go

@@ -247,17 +247,17 @@ func testFilesImpl(t *testing.T, filenames []string, srcs [][]byte, colDelta uin
 					panic("unreachable")
 				}
 			}
-			pattern, err := strconv.Unquote(strings.TrimSpace(pattern))
+			unquoted, err := strconv.Unquote(strings.TrimSpace(pattern))
 			if err != nil {
-				t.Errorf("%s:%d:%d: %v", filename, line, want.Pos.Col(), err)
+				t.Errorf("%s:%d:%d: invalid ERROR pattern (cannot unquote %s)", filename, line, want.Pos.Col(), pattern)
 				continue
 			}
 			if substr {
-				if !strings.Contains(gotMsg, pattern) {
+				if !strings.Contains(gotMsg, unquoted) {
 					continue
 				}
 			} else {
-				rx, err := regexp.Compile(pattern)
+				rx, err := regexp.Compile(unquoted)
 				if err != nil {
 					t.Errorf("%s:%d:%d: %v", filename, line, want.Pos.Col(), err)
 					continue

Diff for: src/go/types/check_test.go

@@ -262,17 +262,17 @@ func testFilesImpl(t *testing.T, filenames []string, srcs [][]byte, manual bool,
 					panic("unreachable")
 				}
 			}
-			pattern, err := strconv.Unquote(strings.TrimSpace(pattern))
+			unquoted, err := strconv.Unquote(strings.TrimSpace(pattern))
 			if err != nil {
-				t.Errorf("%s:%d:%d: %v", filename, line, want.col, err)
+				t.Errorf("%s:%d:%d: invalid ERROR pattern (cannot unquote %s)", filename, line, want.col, pattern)
 				continue
 			}
 			if substr {
-				if !strings.Contains(gotMsg, pattern) {
+				if !strings.Contains(gotMsg, unquoted) {
 					continue
 				}
 			} else {
-				rx, err := regexp.Compile(pattern)
+				rx, err := regexp.Compile(unquoted)
 				if err != nil {
 					t.Errorf("%s:%d:%d: %v", filename, line, want.col, err)
 					continue