go/internal/gccgoimporter: parse optional escape info in export data

Fixes #23324.

Change-Id: Ie2383bad35f0bcc1344a8a1683be08d5fd0eea96
Reviewed-on: https://go-review.googlesource.com/86977Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/go/internal/gccgoimporter/importer_test.go

@@ -102,6 +102,7 @@ var importerTests = [...]importerTest{
 	{pkgpath: "unicode", name: "MaxRune", want: "const MaxRune untyped rune", wantval: "1114111"},
 	{pkgpath: "imports", wantinits: []string{"imports..import", "fmt..import", "math..import"}},
 	{pkgpath: "alias", name: "IntAlias2", want: "type IntAlias2 = Int"},
+	{pkgpath: "escapeinfo", name: "NewT", want: "func NewT(data []byte) *T"},
 }
 
 func TestGoxImporter(t *testing.T) {

src/go/internal/gccgoimporter/parser.go

@@ -226,6 +226,14 @@ func (p *parser) parseField(pkg *types.Package) (field *types.Var, tag string) {
 // Param = Name ["..."] Type .
 func (p *parser) parseParam(pkg *types.Package) (param *types.Var, isVariadic bool) {
 	name := p.parseName()
+	if p.tok == '<' && p.scanner.Peek() == 'e' {
+		// EscInfo = "<esc:" int ">" . (optional and ignored)
+		p.next()
+		p.expectKeyword("esc")
+		p.expect(':')
+		p.expect(scanner.Int)
+		p.expect('>')
+	}
 	if p.tok == '.' {
 		p.next()
 		p.expect('.')

src/go/internal/gccgoimporter/testdata/escapeinfo.go

+// Test case for escape info in export data. To compile and extract .gox file:
+// gccgo -fgo-optimize-allocs -c escapeinfo.go
+// objcopy -j .go_export escapeinfo.o escapeinfo.gox
+
+package escapeinfo
+
+type T struct{ data []byte }
+
+func NewT(data []byte) *T {
+	return &T{data}
+}
+
+func (*T) Read(p []byte) {}