cmd/compile: provide line number for cgo directive error (fix a TODO)

Also: Remove double "go:" prefix in related error message.

Fixes #18882.

Change-Id: Ifbbd8e2f7529b43f035d3dbf7ca4a91f212bc6b6
Reviewed-on: https://go-review.googlesource.com/36121
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/lex.go

@@ -115,7 +115,8 @@ func internString(b []byte) string {
 	return s
 }
 
-func pragcgo(text string) string {
+// pragcgo is called concurrently if files are parsed concurrently.
+func (p *noder) pragcgo(pos src.Pos, text string) string {
 	f := pragmaFields(text)
 
 	verb := f[0][3:] // skip "go:"
@@ -132,7 +133,7 @@ func pragcgo(text string) string {
 			return fmt.Sprintln(verb, local, remote)
 
 		default:
-			yyerror(`usage: //go:%s local [remote]`, verb)
+			p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf(`usage: //go:%s local [remote]`, verb)})
 		}
 	case "cgo_import_dynamic":
 		switch {
@@ -152,7 +153,7 @@ func pragcgo(text string) string {
 			return fmt.Sprintln(verb, local, remote, library)
 
 		default:
-			yyerror(`usage: //go:cgo_import_dynamic local [remote ["library"]]`)
+			p.error(syntax.Error{Pos: pos, Msg: `usage: //go:cgo_import_dynamic local [remote ["library"]]`})
 		}
 	case "cgo_import_static":
 		switch {
@@ -161,7 +162,7 @@ func pragcgo(text string) string {
 			return fmt.Sprintln(verb, local)
 
 		default:
-			yyerror(`usage: //go:cgo_import_static local`)
+			p.error(syntax.Error{Pos: pos, Msg: `usage: //go:cgo_import_static local`})
 		}
 	case "cgo_dynamic_linker":
 		switch {
@@ -170,7 +171,7 @@ func pragcgo(text string) string {
 			return fmt.Sprintln(verb, path)
 
 		default:
-			yyerror(`usage: //go:cgo_dynamic_linker "path"`)
+			p.error(syntax.Error{Pos: pos, Msg: `usage: //go:cgo_dynamic_linker "path"`})
 		}
 	case "cgo_ldflag":
 		switch {
@@ -179,7 +180,7 @@ func pragcgo(text string) string {
 			return fmt.Sprintln(verb, arg)
 
 		default:
-			yyerror(`usage: //go:cgo_ldflag "arg"`)
+			p.error(syntax.Error{Pos: pos, Msg: `usage: //go:cgo_ldflag "arg"`})
 		}
 	}
 	return ""

src/cmd/compile/internal/gc/lex_test.go

@@ -4,7 +4,10 @@
 
 package gc
 
-import "testing"
+import (
+	"cmd/internal/src"
+	"testing"
+)
 
 func eq(a, b []string) bool {
 	if len(a) != len(b) {
@@ -69,8 +72,9 @@ func TestPragcgo(t *testing.T) {
 		{`go:cgo_ldflag "a rg"`, "cgo_ldflag 'a rg'\n"},
 	}
 
+	var p noder
 	for _, tt := range tests {
-		got := pragcgo(tt.in)
+		got := p.pragcgo(src.NoPos, tt.in)
 		if got != tt.want {
 			t.Errorf("pragcgo(%q) = %q; want %q", tt.in, got, tt.want)
 			continue

src/cmd/compile/internal/gc/noder.go

@@ -1105,10 +1105,12 @@ func (p *noder) lineno(n syntax.Node) {
 	lineno = Ctxt.PosTable.XPos(pos)
 }
 
+// error is called concurrently if files are parsed concurrently.
 func (p *noder) error(err error) {
 	p.err <- err.(syntax.Error)
 }
 
+// pragma is called concurrently if files are parsed concurrently.
 func (p *noder) pragma(pos src.Pos, text string) syntax.Pragma {
 	switch {
 	case strings.HasPrefix(text, "line "):
@@ -1124,8 +1126,7 @@ func (p *noder) pragma(pos src.Pos, text string) syntax.Pragma {
 		p.linknames = append(p.linknames, linkname{pos, f[1], f[2]})
 
 	case strings.HasPrefix(text, "go:cgo_"):
-		// TODO(gri): lineno = p.baseline + int32(line) - 1 // pragcgo may call yyerror
-		p.pragcgobuf += pragcgo(text)
+		p.pragcgobuf += p.pragcgo(pos, text)
 		fallthrough // because of //go:cgo_unsafe_args
 	default:
 		verb := text
@@ -1135,7 +1136,7 @@ func (p *noder) pragma(pos src.Pos, text string) syntax.Pragma {
 		prag := pragmaValue(verb)
 		const runtimePragmas = Systemstack | Nowritebarrier | Nowritebarrierrec | Yeswritebarrierrec
 		if !compiling_runtime && prag&runtimePragmas != 0 {
-			p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("//go:%s only allowed in runtime", verb)})
+			p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("//%s only allowed in runtime", verb)})
 		}
 		return prag
 	}

src/go/types/stdlib_test.go

@@ -158,6 +158,7 @@ func TestStdFixed(t *testing.T) {
 		"issue15002.go", // uses Mmap; testTestDir should consult build tags
 		"issue16369.go", // go/types handles this correctly - not an issue
 		"issue18459.go", // go/types doesn't check validity of //go:xxx directives
+		"issue18882.go", // go/types doesn't check validity of //go:xxx directives
 	)
 }
 

test/fixedbugs/issue18459.go

@@ -8,6 +8,6 @@
 
 package main
 
-//go:nowritebarrier // ERROR "go:nowritebarrier only allowed in runtime"
+//go:nowritebarrier // ERROR "//go:nowritebarrier only allowed in runtime"
 func main() {
 }

test/fixedbugs/issue18882.go

+// errorcheck
+
+// Copyright 2017 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.
+
+// Verify that we have a line number for this error.
+
+package main
+
+//go:cgo_ldflag // ERROR "usage: //go:cgo_ldflag"
+func main() {
+}