go/types: use file not parse order for init order computation

The type-checker depended on (token.Pos) position information of
the presented files to determine source order. That information
is determined by the parse order of the files rather than the
order in which the files are presented to the type-checker.

Introduced an order number strictly determined by the file
order as presented to the type-checker and the AST structure
of each file; thus providing source order information even in
the absence of (token.Pos) position information.

Added test case (provided by adonovan).

LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/151160043

go/types/api_test.go

@@ -588,6 +588,39 @@ func TestInitOrderInfo(t *testing.T) {
 	}
 }
 
+func TestMultiFileInitOrder(t *testing.T) {
+	fset := token.NewFileSet()
+	mustParse := func(src string) *ast.File {
+		f, err := parser.ParseFile(fset, "main", src, 0)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return f
+	}
+
+	fileA := mustParse(`package main; var a = 1`)
+	fileB := mustParse(`package main; var b = 2`)
+
+	// The initialization order must not depend on the parse
+	// order of the files, only on the presentation order to
+	// the type-checker.
+	for _, test := range []struct {
+		files []*ast.File
+		want  string
+	}{
+		{[]*ast.File{fileA, fileB}, "[a = 1 b = 2]"},
+		{[]*ast.File{fileB, fileA}, "[b = 2 a = 1]"},
+	} {
+		var info Info
+		if _, err := new(Config).Check("main", fset, test.files, &info); err != nil {
+			t.Fatal(err)
+		}
+		if got := fmt.Sprint(info.InitOrder); got != test.want {
+			t.Fatalf("got %s; want %s", got, test.want)
+		}
+	}
+}
+
 func TestFiles(t *testing.T) {
 	var sources = []string{
 		"package p; type T struct{}; func (T) m1() {}",

go/types/initorder.go

@@ -205,8 +205,8 @@ func (a nodeQueue) Swap(i, j int) {
 func (a nodeQueue) Less(i, j int) bool {
 	x, y := a[i], a[j]
 	// nodes are prioritized by number of incoming dependencies (1st key)
-	// and source positions (2nd key)
+	// and source order (2nd key)
-	return x.in < y.in || x.in == y.in && x.obj.Pos() < y.obj.Pos()
+	return x.in < y.in || x.in == y.in && x.obj.order() < y.obj.order()
 }
 
 func (a *nodeQueue) Push(x interface{}) {

go/types/object.go

@@ -31,9 +31,18 @@ type Object interface {
 	// String returns a human-readable string of the object.
 	String() string
 
+	// order reflects a package-level object's source order: if object
+	// a is before object b in the source, then a.order() < b.order().
+	// order returns a value > 0 for package-level objects; it returns
+	// 0 for all other objects (including objects in file scopes).
+	order() uint32
+
 	// isUsed reports whether the object was marked as 'used'.
 	isUsed() bool
 
+	// setOrder sets the order number of the object. It must be > 0.
+	setOrder(uint32)
+
 	// setParent sets the parent scope of the object.
 	setParent(*Scope)
 
@@ -73,6 +82,8 @@ type object struct {
 	pkg    *Package
 	name   string
 	typ    Type
+
+	order_ uint32
 	used   bool
 }
 
@@ -85,8 +96,10 @@ func (obj *object) Exported() bool { return ast.IsExported(obj.name) }
 func (obj *object) Id() string     { return Id(obj.pkg, obj.name) }
 func (obj *object) String() string { panic("abstract") }
 
-func (obj *object) isUsed() bool { return obj.used }
+func (obj *object) order() uint32 { return obj.order_ }
+func (obj *object) isUsed() bool  { return obj.used }
 
+func (obj *object) setOrder(order uint32)   { assert(order > 0); obj.order_ = order }
 func (obj *object) setParent(parent *Scope) { obj.parent = parent }
 
 func (obj *object) sameId(pkg *Package, name string) bool {
@@ -118,7 +131,7 @@ type PkgName struct {
 }
 
 func NewPkgName(pos token.Pos, pkg *Package, name string, imported *Package) *PkgName {
-	return &PkgName{object{nil, pos, pkg, name, Typ[Invalid], false}, imported}
+	return &PkgName{object{nil, pos, pkg, name, Typ[Invalid], 0, false}, imported}
 }
 
 // Imported returns the package that was imported.
@@ -134,7 +147,7 @@ type Const struct {
 }
 
 func NewConst(pos token.Pos, pkg *Package, name string, typ Type, val exact.Value) *Const {
-	return &Const{object: object{nil, pos, pkg, name, typ, false}, val: val}
+	return &Const{object: object{nil, pos, pkg, name, typ, 0, false}, val: val}
 }
 
 func (obj *Const) Val() exact.Value { return obj.val }
@@ -145,7 +158,7 @@ type TypeName struct {
 }
 
 func NewTypeName(pos token.Pos, pkg *Package, name string, typ Type) *TypeName {
-	return &TypeName{object{nil, pos, pkg, name, typ, false}}
+	return &TypeName{object{nil, pos, pkg, name, typ, 0, false}}
 }
 
 // A Variable represents a declared variable (including function parameters and results, and struct fields).
@@ -158,15 +171,15 @@ type Var struct {
 }
 
 func NewVar(pos token.Pos, pkg *Package, name string, typ Type) *Var {
-	return &Var{object: object{nil, pos, pkg, name, typ, false}}
+	return &Var{object: object{nil, pos, pkg, name, typ, 0, false}}
 }
 
 func NewParam(pos token.Pos, pkg *Package, name string, typ Type) *Var {
-	return &Var{object: object{nil, pos, pkg, name, typ, true}} // parameters are always 'used'
+	return &Var{object: object{nil, pos, pkg, name, typ, 0, true}} // parameters are always 'used'
 }
 
 func NewField(pos token.Pos, pkg *Package, name string, typ Type, anonymous bool) *Var {
-	return &Var{object: object{nil, pos, pkg, name, typ, false}, anonymous: anonymous, isField: true}
+	return &Var{object: object{nil, pos, pkg, name, typ, 0, false}, anonymous: anonymous, isField: true}
 }
 
 func (obj *Var) Anonymous() bool { return obj.anonymous }
@@ -186,7 +199,7 @@ func NewFunc(pos token.Pos, pkg *Package, name string, sig *Signature) *Func {
 	if sig != nil {
 		typ = sig
 	}
-	return &Func{object{nil, pos, pkg, name, typ, false}}
+	return &Func{object{nil, pos, pkg, name, typ, 0, false}}
 }
 
 // FullName returns the package- or receiver-type-qualified name of

go/types/ordering.go

@@ -123,5 +123,5 @@ func orderedSetObjects(set map[Object]bool) []Object {
 type inSourceOrder []Object
 
 func (a inSourceOrder) Len() int           { return len(a) }
-func (a inSourceOrder) Less(i, j int) bool { return a[i].Pos() < a[j].Pos() }
+func (a inSourceOrder) Less(i, j int) bool { return a[i].order() < a[j].order() }
 func (a inSourceOrder) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

go/types/resolver.go

@@ -110,6 +110,7 @@ func (check *Checker) declarePkgObj(ident *ast.Ident, obj Object, d *declInfo) {
 
 	check.declare(check.pkg.scope, ident, obj)
 	check.objMap[obj] = d
+	obj.setOrder(uint32(len(check.objMap)))
 }
 
 // collectObjects collects all file and package objects and inserts them
@@ -341,6 +342,7 @@ func (check *Checker) collectObjects() {
 				}
 				info := &declInfo{file: fileScope, fdecl: d}
 				check.objMap[obj] = info
+				obj.setOrder(uint32(len(check.objMap)))
 
 			default:
 				check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)