[#873] fix json output of -compileonly (#874)

The errorToJSON() method in shell/errors_to_json.go checks whether the error returned is a *parse.MultiError. However, rather than a pointer to a MultiError, an instance was being passed in. Updated the the instance methods of MultiError to take pointers as receivers to be in line with what was expected. This further required updating some other references.

cliedit/highlight/highlight.go

@@ -26,7 +26,7 @@ func highlight(code string, dep Dep, lateCb func(styled.Text)) (styled.Text, []e
 
 	n, errParse := parse.AsChunk("[interactive]", code)
 	if errParse != nil {
-		for _, err := range errParse.(parse.MultiError).Entries {
+		for _, err := range errParse.(*parse.MultiError).Entries {
 			if err.Context.Begin != len(code) {
 				errors = append(errors, err)
 			}

edit/edcore/edit.go

@@ -273,7 +273,7 @@ func atEnd(e error, n int) bool {
 	switch e := e.(type) {
 	case *eval.CompilationError:
 		return e.Context.Begin == n
-	case parse.MultiError:
+	case *parse.MultiError:
 		for _, entry := range e.Entries {
 			if entry.Context.Begin != n {
 				return false

parse/error.go

@@ -23,7 +23,7 @@ func (me *MultiError) add(msg string, ctx *diag.SourceRange) {
 }
 
 // Error returns a string representation of the error.
-func (me MultiError) Error() string {
+func (me *MultiError) Error() string {
 	switch len(me.Entries) {
 	case 0:
 		return "no parse error"
@@ -44,7 +44,7 @@ func (me MultiError) Error() string {
 }
 
 // PPrint pretty-prints the error.
-func (me MultiError) PPrint(indent string) string {
+func (me *MultiError) PPrint(indent string) string {
 	switch len(me.Entries) {
 	case 0:
 		return "no parse error"

parse/parse_test.go

@@ -279,7 +279,7 @@ func TestParseError(t *testing.T) {
 			t.Errorf("Parse(%q) returns no error", tc.src)
 			continue
 		}
-		posErr0 := err.(MultiError).Entries[0]
+		posErr0 := err.(*MultiError).Entries[0]
 		if posErr0.Context.Begin != tc.pos {
 			t.Errorf("Parse(%q) first error begins at %d, want %d. Errors are:%s\n", tc.src, posErr0.Context.Begin, tc.pos, err)
 		}

parse/parser.go

@@ -65,7 +65,7 @@ func (ps *parser) done() {
 // Assembles all parsing errors as one, or returns nil if there were no errors.
 func (ps *parser) assembleError() error {
 	if len(ps.errors.Entries) > 0 {
-		return ps.errors
+		return &ps.errors
 	}
 	return nil
 }