1 files changed, 48 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/syntax/testing_test.go b/src/cmd/compile/internal/syntax/testing_test.go
new file mode 100644
index 0000000..7e439c5
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testing_test.go
@@ -0,0 +1,48 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package syntax
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+	"testing"
+)
+
+func TestCommentMap(t *testing.T) {
+	const src = `/* ERROR "0:0" */ /* ERROR "0:0" */ // ERROR "0:0"
+// ERROR "0:0"
+x /* ERROR "3:1" */                // ignore automatically inserted semicolon here
+/* ERROR "3:1" */                  // position of x on previous line
+   x /* ERROR "5:4" */ ;           // do not ignore this semicolon
+/* ERROR "5:24" */                 // position of ; on previous line
+	package /* ERROR "7:2" */  // indented with tab
+        import  /* ERROR "8:9" */  // indented with blanks
+`
+	m := CommentMap(strings.NewReader(src), regexp.MustCompile("^ ERROR "))
+	found := 0 // number of errors found
+	for line, errlist := range m {
+		for _, err := range errlist {
+			if err.Pos.Line() != line {
+				t.Errorf("%v: got map line %d; want %d", err, err.Pos.Line(), line)
+				continue
+			}
+			// err.Pos.Line() == line
+
+			got := strings.TrimSpace(err.Msg[len(" ERROR "):])
+			want := fmt.Sprintf(`"%d:%d"`, line, err.Pos.Col())
+			if got != want {
+				t.Errorf("%v: got msg %q; want %q", err, got, want)
+				continue
+			}
+			found++
+		}
+	}
+
+	want := strings.Count(src, " ERROR ")
+	if found != want {
+		t.Errorf("CommentMap got %d errors; want %d", found, want)
+	}
+}