go/internal/gccgoimporter: handle conversions in exported const values

Same as https://go-review.googlesource.com/c/33412/ in the standard library.

Fixes #17981.

Change-Id: Iaf47872840a4456d824ed5d7b3eda205c043e4cf
Reviewed-on: https://go-review.googlesource.com/34110
Reviewed-by: Robert Griesemer <gri@golang.org>

go/internal/gccgoimporter/importer.go

@@ -65,6 +65,7 @@ func findExportFile(searchpaths []string, pkgpath string) (string, error) {
 
 const (
 	gccgov1Magic    = "v1;\n"
+	gccgov2Magic    = "v2;\n"
 	goimporterMagic = "\n$$ "
 	archiveMagic    = "!<ar"
 )
@@ -93,7 +94,7 @@ func openExportFile(fpath string) (reader io.ReadSeeker, closer io.Closer, err e
 
 	var elfreader io.ReaderAt
 	switch string(magic[:]) {
-	case gccgov1Magic, goimporterMagic:
+	case gccgov1Magic, gccgov2Magic, goimporterMagic:
 		// Raw export data.
 		reader = f
 		return
@@ -170,7 +171,7 @@ func GetImporter(searchpaths []string, initmap map[*types.Package]InitData) Impo
 		}
 
 		switch string(magic[:]) {
-		case gccgov1Magic:
+		case gccgov1Magic, gccgov2Magic:
 			var p parser
 			p.init(fpath, reader, imports)
 			pkg = p.parsePackage()

go/internal/gccgoimporter/importer_test.go

@@ -96,6 +96,7 @@ var importerTests = [...]importerTest{
 	{pkgpath: "complexnums", name: "NP", want: "const NP untyped complex", wantval: "(-1 + 1i)"},
 	{pkgpath: "complexnums", name: "PN", want: "const PN untyped complex", wantval: "(1 + -1i)"},
 	{pkgpath: "complexnums", name: "PP", want: "const PP untyped complex", wantval: "(1 + 1i)"},
+	{pkgpath: "conversions", name: "Bits", want: "const Bits Units", wantval: `"bits"`},
 	// TODO: enable this entry once bug has been tracked down
 	//{pkgpath: "imports", wantinits: []string{"imports..import", "fmt..import", "math..import"}},
 }

go/internal/gccgoimporter/parser.go

@@ -21,6 +21,7 @@ import (
 
 type parser struct {
 	scanner  scanner.Scanner
+	version  string                    // format version
 	tok      rune                      // current token
 	lit      string                    // literal string; only valid for Ident, Int, String tokens
 	pkgpath  string                    // package path of imported package
@@ -247,9 +248,20 @@ func (p *parser) parseVar(pkg *types.Package) *types.Var {
 	return types.NewVar(token.NoPos, pkg, name, p.parseType(pkg))
 }
 
-// ConstValue     = string | "false" | "true" | ["-"] (int ["'"] | FloatOrComplex) .
+// Conversion = "convert" "(" Type "," ConstValue ")" .
+func (p *parser) parseConversion(pkg *types.Package) (val constant.Value, typ types.Type) {
+	p.expectKeyword("convert")
+	p.expect('(')
+	typ = p.parseType(pkg)
+	p.expect(',')
+	val, _ = p.parseConstValue(pkg)
+	p.expect(')')
+	return
+}
+
+// ConstValue     = string | "false" | "true" | ["-"] (int ["'"] | FloatOrComplex) | Conversion .
 // FloatOrComplex = float ["i" | ("+"|"-") float "i"] .
-func (p *parser) parseConstValue() (val constant.Value, typ types.Type) {
+func (p *parser) parseConstValue(pkg *types.Package) (val constant.Value, typ types.Type) {
 	switch p.tok {
 	case scanner.String:
 		str := p.parseString()
@@ -264,6 +276,9 @@ func (p *parser) parseConstValue() (val constant.Value, typ types.Type) {
 		case "true":
 			b = true
 
+		case "convert":
+			return p.parseConversion(pkg)
+
 		default:
 			p.errorf("expected const value, got %s (%q)", scanner.TokenString(p.tok), p.lit)
 		}
@@ -350,7 +365,7 @@ func (p *parser) parseConst(pkg *types.Package) *types.Const {
 		typ = p.parseType(pkg)
 	}
 	p.expect('=')
-	val, vtyp := p.parseConstValue()
+	val, vtyp := p.parseConstValue(pkg)
 	if typ == nil {
 		typ = vtyp
 	}
@@ -725,7 +740,7 @@ func (p *parser) maybeCreatePackage() {
 	}
 }
 
-// InitDataDirective = "v1" ";" |
+// InitDataDirective = ( "v1" | "v2" ) ";" |
 //                     "priority" int ";" |
 //                     "init" { PackageInit } ";" |
 //                     "checksum" unquotedString ";" .
@@ -736,7 +751,8 @@ func (p *parser) parseInitDataDirective() {
 	}
 
 	switch p.lit {
-	case "v1":
+	case "v1", "v2":
+		p.version = p.lit
 		p.next()
 		p.expect(';')
 
@@ -768,8 +784,9 @@ func (p *parser) parseInitDataDirective() {
 }
 
 // Directive = InitDataDirective |
-//             "package" unquotedString ";" |
+//             "package" unquotedString [ unquotedString ] [ unquotedString ] ";" |
 //             "pkgpath" unquotedString ";" |
+//             "prefix" unquotedString ";" |
 //             "import" unquotedString unquotedString string ";" |
 //             "func" Func ";" |
 //             "type" Type ";" |
@@ -782,13 +799,17 @@ func (p *parser) parseDirective() {
 	}
 
 	switch p.lit {
-	case "v1", "priority", "init", "checksum":
+	case "v1", "v2", "priority", "init", "checksum":
 		p.parseInitDataDirective()
 
 	case "package":
 		p.next()
 		p.pkgname = p.parseUnquotedString()
 		p.maybeCreatePackage()
+		if p.version == "v2" && p.tok != ';' {
+			p.parseUnquotedString()
+			p.parseUnquotedString()
+		}
 		p.expect(';')
 
 	case "pkgpath":
@@ -797,6 +818,11 @@ func (p *parser) parseDirective() {
 		p.maybeCreatePackage()
 		p.expect(';')
 
+	case "prefix":
+		p.next()
+		p.pkgpath = p.parseUnquotedString()
+		p.expect(';')
+
 	case "import":
 		p.next()
 		pkgname := p.parseUnquotedString()

go/internal/gccgoimporter/testdata/conversions.go

@@ -0,0 +1,5 @@
+package conversions
+
+type Units string
+
+const Bits = Units("bits")

go/internal/gccgoimporter/testdata/conversions.gox

@@ -0,0 +1,6 @@
+v2;
+package conversions;
+prefix go;
+package conversions go.conversions go.conversions;
+const Bits <type 1 "Units" <type -16>> = convert(<type 1>, "bits");
+type <type 1>;