[dev.typeparams] cmd/compile/internal/syntax: add utility functions for testing

Preparation step for types2 package.

Change-Id: I8f9557b1a48ad570ba38aac7b720e639218dc6a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/263623
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 45 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 0000000000..d34e5eafaf
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testing_test.go
@@ -0,0 +1,45 @@
+// 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"
+	"strings"
+	"testing"
+)
+
+func TestErrorMap(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 5:22 */                 // position of ; on previous line
+	package /* ERROR 7:2 */  // indented with tab
+        import  /* ERROR 8:9 */  // indented with blanks
+`
+	m := ErrorMap(strings.NewReader(src))
+	got := 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
+			msg := fmt.Sprintf("%d:%d", line, err.Pos.Col())
+			if err.Msg != msg {
+				t.Errorf("%v: got msg %q; want %q", err, err.Msg, msg)
+				continue
+			}
+		}
+		got += len(errlist)
+	}
+
+	want := strings.Count(src, "ERROR")
+	if got != want {
+		t.Errorf("ErrorMap got %d errors; want %d", got, want)
+	}
+}