gc: fix reflect table method receiver

Fixes #451.
Fixes #770.

R=ken2
CC=golang-dev
https://golang.org/cl/2207045

doc/go_spec.html

@@ -5168,6 +5168,6 @@ The following minimal alignment properties are guaranteed:
 <h2 id="Implementation_differences"><span class="alert">Implementation differences - TODO</span></h2>
 <ul>
 	<li><span class="alert">Implementation does not honor the restriction on goto statements and targets (no intervening declarations).</span></li>
-	<li><span class="alert">Method expressions are partially implemented.</span></li>
+	<li><span class="alert">Gccgo: Method expressions are partially implemented.</span></li>
 	<li><span class="alert">Gccgo: allows only one init() function per source file.</span></li>
 </ul>

src/cmd/gc/go.h

@@ -1010,7 +1010,7 @@ void	walkrange(Node *n);
  *	reflect.c
  */
 void	dumptypestructs(void);
-Type*	methodfunc(Type *f, int use_receiver);
+Type*	methodfunc(Type *f, Type*);
 Node*	typename(Type *t);
 Sym*	typesym(Type *t);
 

src/cmd/gc/reflect.c

@@ -100,16 +100,16 @@ lsort(Sig *l, int(*f)(Sig*, Sig*))
  * return function type, receiver as first argument (or not).
  */
 Type*
-methodfunc(Type *f, int use_receiver)
+methodfunc(Type *f, Type *receiver)
 {
 	NodeList *in, *out;
 	Node *d;
 	Type *t;
 
 	in = nil;
-	if(use_receiver) {
+	if(receiver) {
 		d = nod(ODCLFIELD, N, N);
-		d->type = getthisx(f)->type->type;
+		d->type = receiver;
 		in = list(in, d);
 	}
 	for(t=getinargx(f)->type; t; t=t->down) {
@@ -185,8 +185,8 @@ methods(Type *t)
 		a->name = method->name;
 		a->isym = methodsym(method, it, 1);
 		a->tsym = methodsym(method, t, 0);
-		a->type = methodfunc(f->type, 1);
-		a->mtype = methodfunc(f->type, 0);
+		a->type = methodfunc(f->type, t);
+		a->mtype = methodfunc(f->type, nil);
 
 		if(!(a->isym->flags & SymSiggen)) {
 			a->isym->flags |= SymSiggen;
@@ -241,22 +241,27 @@ imethods(Type *t)
 	Sig *a, *all, *last;
 	int o;
 	Type *f;
+	Sym *method, *isym;
+	Prog *oldlist;
 
 	all = nil;
 	last = nil;
 	o = 0;
+	oldlist = nil;
 	for(f=t->type; f; f=f->down) {
 		if(f->etype != TFIELD)
 			fatal("imethods: not field");
 		if(f->type->etype != TFUNC || f->sym == nil)
 			continue;
+		method = f->sym;
 		a = mal(sizeof(*a));
-		a->name = f->sym->name;
-		if(!exportname(f->sym->name))
-			a->pkg = f->sym->pkg;
+		a->name = method->name;
+		if(!exportname(method->name))
+			a->pkg = method->pkg;
 		a->mtype = f->type;
 		a->offset = 0;
-		a->type = methodfunc(f->type, 0);
+		a->type = methodfunc(f->type, nil);
+
 		if(last && sigcmp(last, a) >= 0)
 			fatal("sigcmp vs sortinter %s %s", last->name, a->name);
 		if(last == nil)
@@ -264,7 +269,43 @@ imethods(Type *t)
 		else
 			last->link = a;
 		last = a;
+		
+		// Compiler can only refer to wrappers for
+		// named interface types.
+		if(t->sym == S)
+			continue;
+		
+		// NOTE(rsc): Perhaps an oversight that
+		// IfaceType.Method is not in the reflect data.
+		// Generate the method body, so that compiled
+		// code can refer to it.
+		isym = methodsym(method, t, 0);
+		if(!(isym->flags & SymSiggen)) {
+			isym->flags |= SymSiggen;
+			if(oldlist == nil)
+				oldlist = pc;
+			genwrapper(t, f, isym, 0);
+		}
+		
+		// Generate wrapper for pointer to interface type.
+		isym = methodsym(method, ptrto(t), 0);
+		if(!(isym->flags & SymSiggen)) {
+			isym->flags |= SymSiggen;
+			if(oldlist == nil)
+				oldlist = pc;
+			genwrapper(ptrto(t), f, isym, 0);
+		}
 	}
+
+	if(oldlist) {
+		// old list ended with AEND; change to ANOP
+		// so that the trampolines that follow can be found.
+		nopout(oldlist);
+
+		// start new data list
+		newplist();
+	}
+
 	return all;
 }
 

src/cmd/gc/typecheck.c

@@ -17,6 +17,7 @@ static void	implicitstar(Node**);
 static int	onearg(Node*, char*, ...);
 static int	twoarg(Node*);
 static int	lookdot(Node*, Type*, int);
+static int	looktypedot(Node*, Type*, int);
 static void	typecheckaste(int, int, Type*, NodeList*, char*);
 static Type*	lookdot1(Sym *s, Type *t, Type *f, int);
 static int	nokeys(NodeList*);
@@ -497,6 +498,28 @@ reswitch:
 			yyerror("rhs of . must be a name");	// impossible
 			goto error;
 		}
+		sym = n->right->sym;
+		if(l->op == OTYPE) {
+			if(!looktypedot(n, t, 0)) {
+				if(looktypedot(n, t, 1))
+					yyerror("%#N undefined (cannot refer to unexported method %S)", n, n->right->sym);
+				else
+					yyerror("%#N undefined (type %T has no method %S)", n, t, n->right->sym);
+				goto error;
+			}
+			if(n->type->etype != TFUNC || n->type->thistuple != 1) {
+				yyerror("type %T has no method %hS", n->left->type, sym);
+				n->type = T;
+				goto error;
+			}
+			n->op = ONAME;
+			n->sym = methodsym(sym, l->type, 0);
+			n->type = methodfunc(n->type, l->type);
+			n->xoffset = 0;
+			n->class = PFUNC;
+			ok = Erv;
+			goto ret;
+		}
 		if(isptr[t->etype]) {
 			t = t->type;
 			if(t == T)
@@ -504,34 +527,13 @@ reswitch:
 			n->op = ODOTPTR;
 			checkwidth(t);
 		}
-		sym = n->right->sym;
 		if(!lookdot(n, t, 0)) {
 			if(lookdot(n, t, 1))
-				yyerror("%#N undefined (cannot refer to unexported field %S)", n, n->right->sym);
+				yyerror("%#N undefined (cannot refer to unexported field or method %S)", n, n->right->sym);
 			else
-				yyerror("%#N undefined (type %T has no field %S)", n, t, n->right->sym);
+				yyerror("%#N undefined (type %T has no field or method %S)", n, t, n->right->sym);
 			goto error;
 		}
-		if(l->op == OTYPE) {
-			if(n->type->etype != TFUNC || n->type->thistuple != 1) {
-				yyerror("type %T has no method %hS", n->left->type, sym);
-				n->type = T;
-				goto error;
-			}
-			if(t->etype == TINTER) {
-				yyerror("method expression on interface not implemented");
-				n->type = T;
-				goto error;
-			}
-			n->op = ONAME;
-			n->sym = methodsym(sym, l->type, 0);
-			n->type = methodfunc(n->type, 1);
-			n->xoffset = 0;
-			getinargx(n->type)->type->type = l->type;	// fix up receiver
-			n->class = PFUNC;
-			ok = Erv;
-			goto ret;
-		}
 		switch(n->op) {
 		case ODOTINTER:
 		case ODOTMETH:
@@ -1381,6 +1383,55 @@ lookdot1(Sym *s, Type *t, Type *f, int dostrcmp)
 	return r;
 }
 
+static int
+looktypedot(Node *n, Type *t, int dostrcmp)
+{
+	Type *f1, *f2, *tt;
+	Sym *s;
+	
+	s = n->right->sym;
+
+	if(t->etype == TINTER) {
+		f1 = lookdot1(s, t, t->type, dostrcmp);
+		if(f1 == T)
+			return 0;
+
+		if(f1->width == BADWIDTH)
+			fatal("lookdot badwidth %T %p", f1, f1);
+		n->right = methodname(n->right, t);
+		n->xoffset = f1->width;
+		n->type = f1->type;
+		n->op = ODOTINTER;
+		return 1;
+	}
+
+	tt = t;
+	if(t->sym == S && isptr[t->etype])
+		tt = t->type;
+
+	f2 = methtype(tt);
+	if(f2 == T)
+		return 0;
+
+	expandmeth(f2->sym, f2);
+	f2 = lookdot1(s, f2, f2->xmethod, dostrcmp);
+
+	// disallow T.m if m requires *T receiver
+	if(isptr[getthisx(f2->type)->type->type->etype]
+	&& !isptr[t->etype]
+	&& f2->embedded != 2
+	&& !isifacemethod(f2->type)) {
+		yyerror("invalid method expression %#N (needs pointer receiver: (*%T).%s)", n, t, f2->sym->name);
+		return 0;
+	}
+
+	n->right = methodname(n->right, t);
+	n->xoffset = f2->width;
+	n->type = f2->type;
+	n->op = ODOTMETH;
+	return 1;
+}
+
 static int
 lookdot(Node *n, Type *t, int dostrcmp)
 {
@@ -1394,9 +1445,15 @@ lookdot(Node *n, Type *t, int dostrcmp)
 	if(t->etype == TSTRUCT || t->etype == TINTER)
 		f1 = lookdot1(s, t, t->type, dostrcmp);
 
-	f2 = methtype(n->left->type);
-	if(f2 != T)
-		f2 = lookdot1(s, f2, f2->method, dostrcmp);
+	f2 = T;
+	if(n->left->type == t || n->left->type->sym == S) {
+		f2 = methtype(t);
+		if(f2 != T) {
+			// Use f2->method, not f2->xmethod: adddot has
+			// already inserted all the necessary embedded dots.
+			f2 = lookdot1(s, f2, f2->method, dostrcmp);
+		}
+	}
 
 	if(f1 != T) {
 		if(f2 != T)
@@ -1420,7 +1477,7 @@ lookdot(Node *n, Type *t, int dostrcmp)
 		tt = n->left->type;
 		dowidth(tt);
 		rcvr = getthisx(f2->type)->type->type;
-		if(n->left->op != OTYPE && !eqtype(rcvr, tt)) {
+		if(!eqtype(rcvr, tt)) {
 			if(rcvr->etype == tptr && eqtype(rcvr->type, tt)) {
 				checklvalue(n->left, "call pointer method on");
 				addrescapes(n->left);

src/pkg/reflect/all_test.go

@@ -1046,6 +1046,11 @@ func TestMethod(t *testing.T) {
 		t.Errorf("Type Method returned %d; want 250", i)
 	}
 
+	i = Typeof(&p).Method(0).Func.Call([]Value{NewValue(&p), NewValue(10)})[0].(*IntValue).Get()
+	if i != 250 {
+		t.Errorf("Pointer Type Method returned %d; want 250", i)
+	}
+
 	// Curried method of value.
 	i = NewValue(p).Method(0).Call([]Value{NewValue(10)})[0].(*IntValue).Get()
 	if i != 250 {
@@ -1288,9 +1293,12 @@ func TestDotDotDot(t *testing.T) {
 	t.Error(s)
 }
 
-type inner struct{}
+type inner struct {
+	x int
+}
 
 type outer struct {
+	y int
 	inner
 }
 
@@ -1307,3 +1315,42 @@ func TestNestedMethods(t *testing.T) {
 		}
 	}
 }
+
+type innerInt struct {
+	x int
+}
+
+type outerInt struct {
+	y int
+	innerInt
+}
+
+func (i *innerInt) m() int {
+	return i.x
+}
+
+func TestEmbeddedMethods(t *testing.T) {
+	typ := Typeof((*outerInt)(nil))
+	if typ.NumMethod() != 1 || typ.Method(0).Func.Get() != NewValue((*outerInt).m).(*FuncValue).Get() {
+		t.Errorf("Wrong method table for outerInt: (m=%p)", (*outerInt).m)
+		for i := 0; i < typ.NumMethod(); i++ {
+			m := typ.Method(i)
+			t.Errorf("\t%d: %s %#x\n", i, m.Name, m.Func.Get())
+		}
+	}
+
+	i := &innerInt{3}
+	if v := NewValue(i).Method(0).Call(nil)[0].(*IntValue).Get(); v != 3 {
+		t.Errorf("i.m() = %d, want 3", v)
+	}
+
+	o := &outerInt{1, innerInt{2}}
+	if v := NewValue(o).Method(0).Call(nil)[0].(*IntValue).Get(); v != 2 {
+		t.Errorf("i.m() = %d, want 2", v)
+	}
+
+	f := (*outerInt).m
+	if v := f(o); v != 2 {
+		t.Errorf("f(o) = %d, want 2", v)
+	}
+}

src/pkg/template/template.go

@@ -597,10 +597,7 @@ func lookup(v reflect.Value, name string) reflect.Value {
 			for i := 0; i < n; i++ {
 				m := typ.Method(i)
 				mtyp := m.Type
-				// We must check receiver type because of a bug in the reflection type tables:
-				// it should not be possible to find a method with the wrong receiver type but
-				// this can happen due to value/pointer receiver mismatch.
-				if m.Name == name && mtyp.NumIn() == 1 && mtyp.NumOut() == 1 && mtyp.In(0) == typ {
+				if m.Name == name && mtyp.NumIn() == 1 && mtyp.NumOut() == 1 {
 					return v.Method(i).Call(nil)[0]
 				}
 			}

test/method.go

@@ -19,7 +19,7 @@ func (s S) val() int   { return 1 }
 func (s *S1) val() int { return 2 }
 func (i I) val() int   { return 3 }
 func (i *I1) val() int { return 4 }
-//func (t T) val() int { return 7 }
+func (t T) val() int   { return 7 }
 func (t *T1) val() int { return 8 }
 
 type Val interface {
@@ -34,6 +34,8 @@ func main() {
 	var i I
 	var pi *I1
 	var pt *T1
+	var t T
+	var v Val
 
 	if s.val() != 1 {
 		println("s.val:", s.val())
@@ -75,7 +77,10 @@ func main() {
 		println("(*I1).val(pi):", (*I1).val(pi))
 		panic("fail")
 	}
-	//	if t.val() != 7 { prinln("t.val:", t.val()); panic("fail") }
+	if t.val() != 7 {
+		println("t.val:", t.val())
+		panic("fail")
+	}
 	if pt.val() != 8 {
 		println("pt.val:", pt.val())
 		panic("fail")
@@ -101,11 +106,27 @@ func main() {
 		println("pi.val:", val(pi))
 		panic("fail")
 	}
-	//	if val(t) != 7 { println("t.val:", val(t)); panic("fail") }
+	if val(t) != 7 {
+		println("t.val:", val(t))
+		panic("fail")
+	}
 	if val(pt) != 8 {
 		println("pt.val:", val(pt))
 		panic("fail")
 	}
 
-	//	if Val.val(i) != 3 { println("Val.val(i):", Val.val(i)); panic("fail") }
+	if Val.val(i) != 3 {
+		println("Val.val(i):", Val.val(i))
+		panic("fail")
+	}
+	v = i
+	if Val.val(v) != 3 {
+		println("Val.val(v):", Val.val(v))
+		panic("fail")
+	}
+	pv := &v
+	if pv.val() != 3 {
+		println("pv.val():", pv.val())
+		panic("fail")
+	}
 }

test/method2.go

@@ -6,9 +6,17 @@
 
 package main
 
-type T struct {a int}
+type T struct {
+	a int
+}
 type P *T
 type P1 *T
 
-func (p P) val() int { return 1 }  // ERROR "receiver"
-func (p *P1) val() int { return 1 }  // ERROR "receiver"
+func (p P) val() int   { return 1 } // ERROR "receiver"
+func (p *P1) val() int { return 1 } // ERROR "receiver"
+
+type Val interface {
+	val() int
+}
+
+var _ = (*Val).val // ERROR "method"