go.tools/go/types: simplified init dependency data structures

Preparation for fixing issue 7158.

LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/83160045

go/types/check.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"go/ast"
 	"go/token"
+	"sort"
 
 	"code.google.com/p/go.tools/go/exact"
 )
@@ -84,16 +85,10 @@ func (check *checker) addDeclDep(to Object) {
 	if from == nil {
 		return // not in a package-level init expression
 	}
-	decl := check.objMap[to]
-	if decl == nil || !decl.hasInitializer() {
+	if decl := check.objMap[to]; decl == nil || !decl.hasInitializer() {
 		return // to is not a package-level object or has no initializer
 	}
-	m := from.deps
-	if m == nil {
-		m = make(map[Object]*declInfo)
-		from.deps = m
-	}
-	m[to] = decl
+	from.addDep(to)
 }
 
 func (check *checker) assocMethod(tname string, meth *Func) {
@@ -205,6 +200,17 @@ func (check *checker) handleBailout(err *error) {
 	}
 }
 
+func mapObjects(m map[Object]*declInfo) []Object {
+	list := make([]Object, len(m))
+	i := 0
+	for obj := range m {
+		list[i] = obj
+		i++
+	}
+	sort.Sort(inSourceOrder(list))
+	return list
+}
+
 // Files checks the provided files as part of the checker's package.
 func (check *checker) Files(files []*ast.File) (err error) {
 	defer check.handleBailout(&err)
@@ -213,7 +219,8 @@ func (check *checker) Files(files []*ast.File) (err error) {
 
 	check.collectObjects()
 
-	objList := objectsOf(check.objMap)
+	objList := mapObjects(check.objMap)
+
 	check.packageObjects(objList)
 
 	check.functionBodies()

go/types/resolver.go

@@ -25,8 +25,8 @@ type declInfo struct {
 	init  ast.Expr      // init expression, or nil
 	fdecl *ast.FuncDecl // func declaration, or nil
 
-	deps map[Object]*declInfo // init dependencies; lazily allocated
-	mark int                  // see check.dependencies
+	deps map[Object]bool // init dependencies; lazily allocated
+	mark int             // see check.dependencies
 }
 
 // hasInitializer reports whether the declared object has an initialization
@@ -35,6 +35,16 @@ func (d *declInfo) hasInitializer() bool {
 	return d.init != nil || d.fdecl != nil && d.fdecl.Body != nil
 }
 
+// addDep adds obj as a dependency to d.
+func (d *declInfo) addDep(obj Object) {
+	m := d.deps
+	if m == nil {
+		m = make(map[Object]bool)
+		d.deps = m
+	}
+	m[obj] = true
+}
+
 // arityMatch checks that the lhs and rhs of a const or var decl
 // have the appropriate number of names and init exprs. For const
 // decls, init is the value spec providing the init exprs; for
@@ -378,8 +388,8 @@ func (check *checker) initDependencies(objList []Object) {
 	for _, obj := range objList {
 		switch obj.(type) {
 		case *Const, *Var:
-			if d := check.objMap[obj]; d.hasInitializer() {
-				check.dependencies(obj, d, initPath)
+			if check.objMap[obj].hasInitializer() {
+				check.dependencies(obj, initPath)
 			}
 		}
 	}
@@ -427,16 +437,11 @@ func (check *checker) unusedImports() {
 	}
 }
 
-// TODO(gri) Instead of this support function, introduce type
-// that combines an map[Object]*declInfo and []Object so that
-// we can encapsulate this and don't have to depend on correct
-// Pos() information.
-
-// objectsOf returns the keys of m in source order.
-func objectsOf(m map[Object]*declInfo) []Object {
-	list := make([]Object, len(m))
+func setObjects(set map[Object]bool) []Object {
+	list := make([]Object, len(set))
 	i := 0
-	for obj := range m {
+	for obj := range set {
+		// we don't care about the map element value
 		list[i] = obj
 		i++
 	}
@@ -444,6 +449,11 @@ func objectsOf(m map[Object]*declInfo) []Object {
 	return list
 }
 
+// TODO(gri) Instead of this support function, introduce type
+// that combines an map[Object]*declInfo and []Object so that
+// we can encapsulate this and don't have to depend on correct
+// Pos() information.
+
 // inSourceOrder implements the sort.Sort interface.
 type inSourceOrder []Object
 
@@ -455,8 +465,7 @@ func (a inSourceOrder) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
 // manner and appends the encountered variables in postorder to the Info.InitOrder list.
 // As a result, that list ends up being sorted topologically in the order of dependencies.
 //
-// The current node is represented by the pair (obj, init); and path contains all nodes
-// on the path to the current node (excluding the current node).
+// Path contains all nodes on the path to the current node obj (excluding obj).
 //
 // To detect cyles, the nodes are marked as follows: Initially, all nodes are unmarked
 // (declInfo.mark == 0). On the way down, a node is appended to the path, and the node
@@ -474,7 +483,8 @@ func (a inSourceOrder) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
 // start of the cycle in the path. The tail of the path (path[mark-1:]) contains all
 // nodes of the cycle.
 //
-func (check *checker) dependencies(obj Object, init *declInfo, path []Object) {
+func (check *checker) dependencies(obj Object, path []Object) {
+	init := check.objMap[obj]
 	if init.mark < 0 {
 		return // finished
 	}
@@ -516,9 +526,8 @@ func (check *checker) dependencies(obj Object, init *declInfo, path []Object) {
 
 	path = append(path, obj) // len(path) > 0
 	init.mark = len(path)    // init.mark > 0
-	for _, obj := range objectsOf(init.deps) {
-		dep := init.deps[obj]
-		check.dependencies(obj, dep, path)
+	for _, obj := range setObjects(init.deps) {
+		check.dependencies(obj, path)
 	}
 	init.mark = -1 // init.mark < 0