go.tools/pointer: replace Pointer, PointsToSet interfaces with their sole implementations.

(Elminate premature abstraction.)

The test probes used Pointer!=nil for the "is pointerlike"
predicate. Now that Pointer is a struct, they check the type
of the expression, which is more accurate.  Two probes on
non-pointerlike values have beem removed.

R=crawshaw
CC=golang-dev
https://golang.org/cl/38420043

oracle/peers.go

@@ -88,7 +88,7 @@ func peers(o *Oracle, qpos *QueryPos) (queryResult, error) {
 	var sends, receives []token.Pos
 	for _, op := range ops {
 		for _, ptr := range ptares.Queries[op.ch] {
-			if ptr != nil && ptr.PointsTo().Intersects(queryChanPts) {
+			if ptr.PointsTo().Intersects(queryChanPts) {
 				if op.dir == ast.SEND {
 					sends = append(sends, op.pos)
 				} else {

pointer/api.go

@@ -40,7 +40,10 @@ type Config struct {
 	// Pointer p may be saved until the analysis is complete, at
 	// which point its methods provide access to the analysis
 	// (The result of callings its methods within the Print
-	// callback is undefined.)  p is nil if x is non-pointerlike.
+	// callback is undefined.)
+	//
+	// CanPoint(site.Args[0].Type()) reports whether p is
+	// pointerlike.
 	//
 	Print func(site *ssa.CallCommon, p Pointer)
 
@@ -117,53 +120,26 @@ type Result struct {
 }
 
 // A Pointer is an equivalence class of pointerlike values.
-type Pointer interface {
-	// PointsTo returns the points-to set of this pointer.
-	PointsTo() PointsToSet
-
-	// MayAlias reports whether the receiver pointer may alias
-	// the argument pointer.
-	MayAlias(Pointer) bool
-
-	// Context returns the context of this pointer,
-	// if it corresponds to a local variable.
-	Context() call.GraphNode
-
-	String() string
+//
+// A pointer doesn't have a unique type because pointers of distinct
+// types may alias the same object.
+//
+type Pointer struct {
+	a   *analysis
+	cgn *cgnode
+	n   nodeid // non-zero
 }
 
 // A PointsToSet is a set of labels (locations or allocations).
-//
-type PointsToSet interface {
-	// PointsTo returns the set of labels that this points-to set
-	// contains.
-	Labels() []*Label
-
-	// Intersects reports whether this points-to set and the
-	// argument points-to set contain common members.
-	Intersects(PointsToSet) bool
-
-	// If this PointsToSet came from a Pointer of interface kind
-	// or a reflect.Value, DynamicTypes returns the set of dynamic
-	// types that it may contain.  (For an interface, they will
-	// always be concrete types.)
-	//
-	// The result is a mapping whose keys are the dynamic types to
-	// which it may point.  For each pointer-like key type, the
-	// corresponding map value is a set of pointer abstractions of
-	// that dynamic type, represented as a []Pointer slice.  Use
-	// PointsToCombined to merge them.
-	//
-	// The result is empty unless CanHaveDynamicTypes(T).
-	//
-	DynamicTypes() *typemap.M
+type PointsToSet struct {
+	a   *analysis // may be nil if pts is nil
+	pts nodeset
 }
 
 // Union returns the set containing all the elements of each set in sets.
 func Union(sets ...PointsToSet) PointsToSet {
-	var union ptset
+	var union PointsToSet
 	for _, set := range sets {
-		set := set.(ptset)
 		union.a = set.a
 		union.pts.addAll(set.pts)
 	}
@@ -180,14 +156,7 @@ func PointsToCombined(ptrs []Pointer) PointsToSet {
 	return Union(ptsets...)
 }
 
-// ---- PointsToSet public interface
-
-type ptset struct {
-	a   *analysis // may be nil if pts is nil
-	pts nodeset
-}
-
-func (s ptset) String() string {
+func (s PointsToSet) String() string {
 	var buf bytes.Buffer
 	fmt.Fprintf(&buf, "[")
 	sep := ""
@@ -199,7 +168,9 @@ func (s ptset) String() string {
 	return buf.String()
 }
 
-func (s ptset) Labels() []*Label {
+// PointsTo returns the set of labels that this points-to set
+// contains.
+func (s PointsToSet) Labels() []*Label {
 	var labels []*Label
 	for l := range s.pts {
 		labels = append(labels, s.a.labelFor(l))
@@ -207,7 +178,20 @@ func (s ptset) Labels() []*Label {
 	return labels
 }
 
-func (s ptset) DynamicTypes() *typemap.M {
+// If this PointsToSet came from a Pointer of interface kind
+// or a reflect.Value, DynamicTypes returns the set of dynamic
+// types that it may contain.  (For an interface, they will
+// always be concrete types.)
+//
+// The result is a mapping whose keys are the dynamic types to
+// which it may point.  For each pointer-like key type, the
+// corresponding map value is a set of pointer abstractions of
+// that dynamic type, represented as a []Pointer slice.  Use
+// PointsToCombined to merge them.
+//
+// The result is empty unless CanHaveDynamicTypes(T).
+//
+func (s PointsToSet) DynamicTypes() *typemap.M {
 	var tmap typemap.M
 	tmap.SetHasher(s.a.hasher)
 	for ifaceObjId := range s.pts {
@@ -219,13 +203,14 @@ func (s ptset) DynamicTypes() *typemap.M {
 			panic("indirect tagged object") // implement later
 		}
 		prev, _ := tmap.At(tDyn).([]Pointer)
-		tmap.Set(tDyn, append(prev, ptr{s.a, nil, v}))
+		tmap.Set(tDyn, append(prev, Pointer{s.a, nil, v}))
 	}
 	return &tmap
 }
 
-func (x ptset) Intersects(y_ PointsToSet) bool {
-	y := y_.(ptset)
+// Intersects reports whether this points-to set and the
+// argument points-to set contain common members.
+func (x PointsToSet) Intersects(y PointsToSet) bool {
 	for l := range x.pts {
 		if _, ok := y.pts[l]; ok {
 			return true
@@ -234,31 +219,28 @@ func (x ptset) Intersects(y_ PointsToSet) bool {
 	return false
 }
 
-// ---- Pointer public interface
-
-// ptr adapts a node to the Pointer interface.
-type ptr struct {
-	a   *analysis
-	cgn *cgnode
-	n   nodeid // non-zero
-}
-
-func (p ptr) String() string {
+func (p Pointer) String() string {
 	return fmt.Sprintf("n%d", p.n)
 }
 
-func (p ptr) Context() call.GraphNode {
+// Context returns the context of this pointer,
+// if it corresponds to a local variable.
+func (p Pointer) Context() call.GraphNode {
 	return p.cgn
 }
 
-func (p ptr) PointsTo() PointsToSet {
-	return ptset{p.a, p.a.nodes[p.n].pts}
+// PointsTo returns the points-to set of this pointer.
+func (p Pointer) PointsTo() PointsToSet {
+	return PointsToSet{p.a, p.a.nodes[p.n].pts}
 }
 
-func (p ptr) MayAlias(q Pointer) bool {
+// MayAlias reports whether the receiver pointer may alias
+// the argument pointer.
+func (p Pointer) MayAlias(q Pointer) bool {
 	return p.PointsTo().Intersects(q.PointsTo())
 }
 
-func (p ptr) DynamicTypes() *typemap.M {
+// DynamicTypes returns p.PointsTo().DynamicTypes().
+func (p Pointer) DynamicTypes() *typemap.M {
 	return p.PointsTo().DynamicTypes()
 }

pointer/gen.go

@@ -82,14 +82,14 @@ func (a *analysis) setValueNode(v ssa.Value, id nodeid, cgn *cgnode) {
 
 	// Record the (v, id) relation if the client has queried pts(v).
 	if _, ok := a.config.Queries[v]; ok {
-		a.result.Queries[v] = append(a.result.Queries[v], ptr{a, cgn, id})
+		a.result.Queries[v] = append(a.result.Queries[v], Pointer{a, cgn, id})
 	}
 
 	// Record the (*v, id) relation if the client has queried pts(*v).
 	if _, ok := a.config.IndirectQueries[v]; ok {
 		indirect := a.addNodes(v.Type(), "query.indirect")
 		a.genLoad(cgn, indirect, v, 0, a.sizeof(v.Type()))
-		a.result.IndirectQueries[v] = append(a.result.IndirectQueries[v], ptr{a, cgn, indirect})
+		a.result.IndirectQueries[v] = append(a.result.IndirectQueries[v], Pointer{a, cgn, indirect})
 	}
 }
 
@@ -539,7 +539,7 @@ func (a *analysis) genBuiltinCall(instr ssa.CallInstruction, cgn *cgnode) {
 			if probe == 0 {
 				probe = a.addNodes(t, "print")
 				a.probes[call] = probe
-				Print(call, ptr{a, nil, probe}) // notify client
+				Print(call, Pointer{a, nil, probe}) // notify client
 			}
 
 			a.copy(probe, a.valueNode(call.Args[0]), a.sizeof(t))

pointer/pointer_test.go

@@ -309,9 +309,9 @@ func doOneInput(input, filename string) bool {
 				e.errorf("unreachable print() statement has expectation %s", e)
 				continue
 			}
-			if pr.arg0 == nil {
+			if tArg := pr.instr.Args[0].Type(); !pointer.CanPoint(tArg) {
 				ok = false
-				e.errorf("expectation on non-pointerlike operand: %s", pr.instr.Args[0].Type())
+				e.errorf("expectation on non-pointerlike operand: %s", tArg)
 				continue
 			}
 		}

pointer/testdata/another.go

@@ -31,5 +31,4 @@ func main() {
 	// labels, even though it may contain pointers that do.
 	print(i)                 // @pointsto makeinterface:func(x int) int | makeinterface:func(x int, y int) | makeinterface:func(int, int) | makeinterface:int | makeinterface:main.S
 	print(i.(func(int) int)) // @pointsto main.incr
-	print(i.(S))             // @pointsto
 }

pointer/testdata/structs.go

@@ -87,7 +87,6 @@ func structs2() {
 
 	var s3 S          // @line s2s3
 	s3.c[2] = new(T)  // @line s2s3c
-	print(s3.c)       // @pointsto
 	print(&s3.c)      // @pointsto s3.c@s2s3:6
 	print(s3.c[1])    // @pointsto new@s2s3c:15
 	print(&s3.c[1])   // @pointsto s3.c[*]@s2s3:6