go.tools/go/importer: handle predeclared types consistently

- pre-poluate typIndex and typList using a predefined list of types
- no need to handle basic types explicitly anymore
- removed basicTag
- go/types: exported UniverseByte and UniverseRune for now

LGTM=adonovan
R=adonovan
CC=cmang, golang-codereviews
https://golang.org/cl/65920044

go/importer/export.go

@@ -21,44 +21,6 @@ const (
 	trace = false // print emitted data
 )
 
-const (
-	magic   = "\n$$ exports $$\n"
-	version = "v0"
-)
-
-// Tags. Must be < 0.
-const (
-	// Packages
-	packageTag = -(iota + 1)
-
-	// Objects
-	constTag
-	typeTag
-	varTag
-	funcTag
-
-	// Types
-	basicTag
-	arrayTag
-	sliceTag
-	structTag
-	pointerTag
-	signatureTag
-	interfaceTag
-	mapTag
-	chanTag
-	namedTag
-
-	// Values
-	int64Tag
-	floatTag
-	fractionTag
-	complexTag
-	stringTag
-	falseTag
-	trueTag
-)
-
 // ExportData serializes the interface (exported package objects)
 // of package pkg and returns the corresponding data. The export
 // format is described elsewhere (TODO).
@@ -70,10 +32,9 @@ func ExportData(pkg *types.Package) []byte {
 	}
 
 	// populate typIndex with predeclared types
-	for _, t := range types.Typ[1:] {
+	for _, t := range predeclared {
 		p.typIndex[t] = len(p.typIndex)
 	}
-	p.typIndex[types.Universe.Lookup("error").Type()] = len(p.typIndex)
 
 	if trace {
 		p.tracef("export %s\n", pkg.Name())
@@ -253,16 +214,6 @@ func (p *exporter) typ(typ types.Type) {
 
 	// otherwise, write the type tag (< 0) and type data
 	switch t := typ.(type) {
-	case *types.Basic:
-		// Basic types are pre-recorded and don't usually end up here.
-		// However, the alias types byte and rune are not in the types.Typ
-		// table and get emitted here (once per package, if they appear).
-		// This permits faithful reconstruction of the alias type (i.e.,
-		// keeping the name). If we decide to eliminate the distinction
-		// between the alias types, this code can go.
-		p.int(basicTag)
-		p.string(t.Name())
-
 	case *types.Array:
 		p.int(arrayTag)
 		p.int64(t.Len())

go/importer/import.go

@@ -35,10 +35,9 @@ func ImportData(imports map[string]*types.Package, data []byte) (*types.Package,
 	}
 
 	// populate typList with predeclared types
-	for _, t := range types.Typ[1:] {
+	for _, t := range predeclared {
 		p.typList = append(p.typList, t)
 	}
-	p.typList = append(p.typList, types.Universe.Lookup("error").Type())
 
 	if v := p.string(); v != version {
 		return nil, fmt.Errorf("unknown version: got %s; want %s", v, version)
@@ -199,11 +198,6 @@ func (p *importer) typ() types.Type {
 
 	// otherwise, i is the type tag (< 0)
 	switch i {
-	case basicTag:
-		t := types.Universe.Lookup(p.string()).(*types.TypeName).Type().(*types.Basic)
-		p.record(t)
-		return t
-
 	case arrayTag:
 		t := new(types.Array)
 		p.record(t)

go/importer/predefined.go

@@ -0,0 +1,83 @@
+// Copyright 2014 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 importer
+
+import "code.google.com/p/go.tools/go/types"
+
+const (
+	magic   = "\n$$ exports $$\n"
+	version = "v0"
+)
+
+// Tags. Must be < 0.
+const (
+	// Packages
+	packageTag = -(iota + 1)
+
+	// Objects
+	constTag
+	typeTag
+	varTag
+	funcTag
+
+	// Types
+	arrayTag
+	sliceTag
+	structTag
+	pointerTag
+	signatureTag
+	interfaceTag
+	mapTag
+	chanTag
+	namedTag
+
+	// Values
+	falseTag
+	trueTag
+	int64Tag
+	floatTag
+	fractionTag
+	complexTag
+	stringTag
+)
+
+var predeclared = []types.Type{
+	// basic types
+	types.Typ[types.Bool],
+	types.Typ[types.Int],
+	types.Typ[types.Int8],
+	types.Typ[types.Int16],
+	types.Typ[types.Int32],
+	types.Typ[types.Int64],
+	types.Typ[types.Uint],
+	types.Typ[types.Uint8],
+	types.Typ[types.Uint16],
+	types.Typ[types.Uint32],
+	types.Typ[types.Uint64],
+	types.Typ[types.Uintptr],
+	types.Typ[types.Float32],
+	types.Typ[types.Float64],
+	types.Typ[types.Complex64],
+	types.Typ[types.Complex128],
+	types.Typ[types.String],
+
+	// untyped types
+	types.Typ[types.UntypedBool],
+	types.Typ[types.UntypedInt],
+	types.Typ[types.UntypedRune],
+	types.Typ[types.UntypedFloat],
+	types.Typ[types.UntypedComplex],
+	types.Typ[types.UntypedString],
+	types.Typ[types.UntypedNil],
+
+	// package unsafe
+	types.Typ[types.UnsafePointer],
+
+	// aliases
+	types.UniverseByte,
+	types.UniverseRune,
+
+	types.Universe.Lookup("error").Type(),
+}

go/types/builtins.go

@@ -81,14 +81,14 @@ func (check *checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		// spec: "As a special case, append also accepts a first argument assignable
 		// to type []byte with a second argument of string type followed by ... .
 		// This form appends the bytes of the string.
-		if nargs == 2 && call.Ellipsis.IsValid() && x.assignableTo(check.conf, NewSlice(universeByte)) {
+		if nargs == 2 && call.Ellipsis.IsValid() && x.assignableTo(check.conf, NewSlice(UniverseByte)) {
 			arg(x, 1)
 			if x.mode == invalid {
 				return
 			}
 			if isString(x.typ) {
 				if check.Types != nil {
-					sig := makeSig(S, S, NewSlice(universeByte))
+					sig := makeSig(S, S, NewSlice(UniverseByte))
 					sig.variadic = true
 					check.recordBuiltinType(call.Fun, sig)
 				}
@@ -274,7 +274,7 @@ func (check *checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		switch t := y.typ.Underlying().(type) {
 		case *Basic:
 			if isString(y.typ) {
-				src = universeByte
+				src = UniverseByte
 			}
 		case *Slice:
 			src = t.elem

go/types/expr.go

@@ -1141,7 +1141,7 @@ func (check *checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 				// (not a constant) even if the string and the
 				// index are constant
 				x.mode = value
-				x.typ = universeByte // use 'byte' name
+				x.typ = UniverseByte // use 'byte' name
 			}
 
 		case *Array:

go/types/predicates.go

@@ -295,7 +295,7 @@ func defaultType(typ Type) Type {
 		case UntypedInt:
 			return Typ[Int]
 		case UntypedRune:
-			return universeRune // use 'rune' name
+			return UniverseRune // use 'rune' name
 		case UntypedFloat:
 			return Typ[Float64]
 		case UntypedComplex:

go/types/stmt.go

@@ -609,7 +609,7 @@ func (check *checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		case *Basic:
 			if isString(typ) {
 				key = Typ[Int]
-				val = universeRune // use 'rune' name
+				val = UniverseRune // use 'rune' name
 			}
 		case *Array:
 			key = Typ[Int]

go/types/universe.go

@@ -17,8 +17,8 @@ var (
 	Universe     *Scope
 	Unsafe       *Package
 	universeIota *Const
-	universeByte *Basic
-	universeRune *Basic
+	UniverseByte *Basic // uint8 alias, but has name "byte"
+	UniverseRune *Basic // int32 alias, but has name "rune"
 )
 
 var Typ = [...]*Basic{
@@ -187,8 +187,8 @@ func init() {
 	defPredeclaredFuncs()
 
 	universeIota = Universe.Lookup("iota").(*Const)
-	universeByte = Universe.Lookup("byte").(*TypeName).typ.(*Basic)
-	universeRune = Universe.Lookup("rune").(*TypeName).typ.(*Basic)
+	UniverseByte = Universe.Lookup("byte").(*TypeName).typ.(*Basic)
+	UniverseRune = Universe.Lookup("rune").(*TypeName).typ.(*Basic)
 }
 
 // Objects with names containing blanks are internal and not entered into