go/internal/gccgoimporter: improve alias handling for anonymous fields

The code in the parser that deals with anonymous structure fields
records the fact that a field is anonymous, then tries to install a proxy
name for the field based on the name of the type used to declare
the field. If that type was an alias, the current recipe for determining
the proxy name was not working properly; enhance the code to recover
and report the alias name used.

Fixes #31540.

Change-Id: I9b7369ed558a288b56d85170c6f1144daf5228eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/172603Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/go/internal/gccgoimporter/importer_test.go

@@ -92,6 +92,7 @@ var importerTests = [...]importerTest{
 	{pkgpath: "nointerface", name: "I", want: "type I int"},
 	{pkgpath: "issue29198", name: "FooServer", want: "type FooServer struct{FooServer *FooServer; user string; ctx context.Context}"},
 	{pkgpath: "issue30628", name: "Apple", want: "type Apple struct{hey sync.RWMutex; x int; RQ [517]struct{Count uintptr; NumBytes uintptr; Last uintptr}}"},
+	{pkgpath: "issue31540", name: "S", want: "type S struct{b int; map[Y]Z}"},
 }
 
 func TestGoxImporter(t *testing.T) {

src/go/internal/gccgoimporter/parser.go

@@ -31,6 +31,7 @@ type parser struct {
 	typeData []string                  // unparsed type data (v3 and later)
 	fixups   []fixupRecord             // fixups to apply at end of parsing
 	initdata InitData                  // package init priority data
+	aliases  map[int]string            // maps saved type number to alias name
 }
 
 // When reading export data it's possible to encounter a defined type
@@ -57,6 +58,7 @@ func (p *parser) init(filename string, src io.Reader, imports map[string]*types.
 	p.scanner = new(scanner.Scanner)
 	p.initScanner(filename, src)
 	p.imports = imports
+	p.aliases = make(map[int]string)
 	p.typeList = make([]types.Type, 1 /* type numbers start at 1 */, 16)
 }
 
@@ -238,17 +240,22 @@ func deref(typ types.Type) types.Type {
 // Field = Name Type [string] .
 func (p *parser) parseField(pkg *types.Package) (field *types.Var, tag string) {
 	name := p.parseName()
-	typ := p.parseType(pkg)
+	typ, n := p.parseTypeExtended(pkg)
 	anon := false
 	if name == "" {
 		anon = true
-		switch typ := deref(typ).(type) {
-		case *types.Basic:
-			name = typ.Name()
-		case *types.Named:
-			name = typ.Obj().Name()
-		default:
-			p.error("anonymous field expected")
+		// Alias?
+		if aname, ok := p.aliases[n]; ok {
+			name = aname
+		} else {
+			switch typ := deref(typ).(type) {
+			case *types.Basic:
+				name = typ.Name()
+			case *types.Named:
+				name = typ.Obj().Name()
+			default:
+				p.error("anonymous field expected")
+			}
 		}
 	}
 	field = types.NewField(token.NoPos, pkg, name, typ, anon)
@@ -495,6 +502,7 @@ func (p *parser) parseNamedType(nlist []int) types.Type {
 		}
 		t := p.parseType(pkg, nlist...)
 		obj = types.NewTypeName(token.NoPos, pkg, name, t)
+		p.aliases[nlist[len(nlist)-1]] = name
 		scope.Insert(obj)
 		return t
 	}
@@ -702,7 +710,8 @@ func (p *parser) parseResultList(pkg *types.Package) *types.Tuple {
 		if p.tok == scanner.Ident && p.lit == "inl" {
 			return nil
 		}
-		return types.NewTuple(types.NewParam(token.NoPos, pkg, "", p.parseTypeAfterAngle(pkg)))
+		taa, _ := p.parseTypeAfterAngle(pkg)
+		return types.NewTuple(types.NewParam(token.NoPos, pkg, "", taa))
 
 	case '(':
 		params, _ := p.parseParamList(pkg)
@@ -876,16 +885,18 @@ func lookupBuiltinType(typ int) types.Type {
 //
 func (p *parser) parseType(pkg *types.Package, n ...int) types.Type {
 	p.expect('<')
-	return p.parseTypeAfterAngle(pkg, n...)
+	t, _ := p.parseTypeAfterAngle(pkg, n...)
+	return t
 }
 
 // (*parser).Type after reading the "<".
-func (p *parser) parseTypeAfterAngle(pkg *types.Package, n ...int) (t types.Type) {
+func (p *parser) parseTypeAfterAngle(pkg *types.Package, n ...int) (t types.Type, n1 int) {
 	p.expectKeyword("type")
 
+	n1 = 0
 	switch p.tok {
 	case scanner.Int:
-		n1 := p.parseInt()
+		n1 = p.parseInt()
 		if p.tok == '>' {
 			if len(p.typeData) > 0 && p.typeList[n1] == nil {
 				p.parseSavedType(pkg, n1, n)
@@ -908,7 +919,7 @@ func (p *parser) parseTypeAfterAngle(pkg *types.Package, n ...int) (t types.Type
 
 	default:
 		p.errorf("expected type number, got %s (%q)", scanner.TokenString(p.tok), p.lit)
-		return nil
+		return nil, 0
 	}
 
 	if t == nil || t == reserved {
@@ -919,6 +930,15 @@ func (p *parser) parseTypeAfterAngle(pkg *types.Package, n ...int) (t types.Type
 	return
 }
 
+// parseTypeExtended is identical to parseType, but if the type in
+// question is a saved type, returns the index as well as the type
+// pointer (index returned is zero if we parsed a builtin).
+func (p *parser) parseTypeExtended(pkg *types.Package, n ...int) (t types.Type, n1 int) {
+	p.expect('<')
+	t, n1 = p.parseTypeAfterAngle(pkg, n...)
+	return
+}
+
 // InlineBody = "<inl:NN>" .{NN}
 // Reports whether a body was skipped.
 func (p *parser) skipInlineBody() {

src/go/internal/gccgoimporter/testdata/issue31540.go

+// Copyright 2019 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 issue31540
+
+type Y struct {
+	q int
+}
+
+type Z map[int]int
+
+type X = map[Y]Z
+
+type A1 = X
+
+type A2 = A1
+
+type S struct {
+	b int
+	A2
+}
+
+func Hallo() S {
+	return S{}
+}

src/go/internal/gccgoimporter/testdata/issue31540.gox

+v3;
+package issue31540
+pkgpath issue31540
+types 11 7 23 23 20 22 20 21 57 31 45 36
+type 1 "A1" = <type 4>
+type 2 "A2" = <type 1>
+type 3 "S" <type 7>
+type 4 "X" = <type 8>
+type 5 "Y" <type 9>
+type 6 "Z" <type 10>
+type 7 struct { .go.mapalias.b <type -11>; ? <type 2>; }
+type 8 map [<type 5>] <type 6>
+type 9 struct { .go.mapalias.q <type -11>; }
+type 10 map [<type -11>] <type -11>
+func Hallo () <type 3>
+checksum C3FAF2524A90BC11225EE65D059BF27DFB69134B