gc: fix order of evaluation

Pulling function calls out to happen before the
expression being evaluated was causing illegal
reorderings even without inlining; with inlining
it got worse.  This CL adds a separate ordering pass
to move things with a fixed order out of expressions
and into the statement sequence, where they will
not be reordered by walk.

Replaces lvd's CL 5534079.

Fixes #2740.

R=lvd
CC=golang-dev
https://golang.org/cl/5569062

src/cmd/gc/Makefile

@@ -34,6 +34,7 @@ OFILES=\
 	mparith2.$O\
 	mparith3.$O\
 	obj.$O\
+	order.$O\
 	range.$O\
 	reflect.$O\
 	select.$O\

src/cmd/gc/fmt.c

@@ -1263,8 +1263,12 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case OMAKEMAP:
 	case OMAKECHAN:
 	case OMAKESLICE:
-		if(n->list->next)
-			return fmtprint(f, "make(%T, %,H)", n->type, n->list->next);
+		if(n->list) // pre-typecheck
+			return fmtprint(f, "make(%T, %,H)", n->type, n->list);
+		if(n->right)
+			return fmtprint(f, "make(%T, %N, %N)", n->type, n->left, n->right);
+		if(n->left)
+			return fmtprint(f, "make(%T, %N)", n->type, n->left);
 		return fmtprint(f, "make(%T)", n->type);
 
 	// Unary

src/cmd/gc/gen.c

@@ -826,5 +826,6 @@ temp(Type *t)
 	
 	n = nod(OXXX, N, N);
 	tempname(n, t);
+	n->sym->def->used = 1;
 	return n;
 }

src/cmd/gc/go.h

@@ -1088,6 +1088,11 @@ void	dumpobj(void);
 void	ieeedtod(uint64 *ieee, double native);
 Sym*	stringsym(char*, int);
 
+/*
+ *	order.c
+ */
+void	order(Node *fn);
+
 /*
  *	range.c
  */
@@ -1124,6 +1129,7 @@ int	stataddr(Node *nam, Node *n);
  */
 Node*	adddot(Node *n);
 int	adddot1(Sym *s, Type *t, int d, Type **save, int ignorecase);
+void	addinit(Node**, NodeList*);
 Type*	aindex(Node *b, Type *t);
 int	algtype(Type *t);
 int	algtype1(Type *t, Type **bad);
@@ -1135,6 +1141,7 @@ int	brcom(int a);
 int	brrev(int a);
 NodeList*	concat(NodeList *a, NodeList *b);
 int	convertop(Type *src, Type *dst, char **why);
+Node*	copyexpr(Node*, Type*, NodeList**);
 int	count(NodeList *l);
 int	cplxsubtype(int et);
 int	eqtype(Type *t1, Type *t2);

src/cmd/gc/inl.c

@@ -225,6 +225,7 @@ static void
 inlconv2stmt(Node *n)
 {
 	n->op = OBLOCK;
+	// n->ninit stays
 	n->list = n->nbody;
 	n->nbody = nil;
 	n->rlist = nil;
@@ -232,13 +233,14 @@ inlconv2stmt(Node *n)
 
 // Turn an OINLCALL into a single valued expression.
 static void
-inlconv2expr(Node *n)
+inlconv2expr(Node **np)
 {
-	n->op = OCONVNOP;
-	n->left = n->rlist->n;
-	n->rlist = nil;
-	n->ninit = concat(n->ninit, n->nbody);
-	n->nbody = nil;
+	Node *n, *r;
+	
+	n = *np;
+	r = n->rlist->n;
+	addinit(&r, concat(n->ninit, n->nbody));
+	*np = r;
 }
 
 // Turn the OINLCALL in n->list into an expression list on n.
@@ -248,7 +250,7 @@ inlgluelist(Node *n)
 {
 	Node *c;
 
-	c = n->list->n;
+	c = n->list->n;  // this is the OINLCALL
 	n->ninit = concat(n->ninit, c->ninit);
 	n->ninit = concat(n->ninit, c->nbody);
 	n->list  = c->rlist;
@@ -261,7 +263,7 @@ inlgluerlist(Node *n)
 {
 	Node *c;
 
-	c = n->rlist->n;
+	c = n->rlist->n;  // this is the OINLCALL
 	n->ninit = concat(n->ninit, c->ninit);
 	n->ninit = concat(n->ninit, c->nbody);
 	n->rlist = c->rlist;
@@ -322,11 +324,11 @@ inlnode(Node **np)
 
 	inlnode(&n->left);
 	if(n->left && n->left->op == OINLCALL)
-		inlconv2expr(n->left);
+		inlconv2expr(&n->left);
 
 	inlnode(&n->right);
 	if(n->right && n->right->op == OINLCALL)
-		inlconv2expr(n->right);
+		inlconv2expr(&n->right);
 
 	inlnodelist(n->list);
 	switch(n->op) {
@@ -359,7 +361,7 @@ inlnode(Node **np)
 	list_dflt:
 		for(l=n->list; l; l=l->next)
 			if(l->n->op == OINLCALL)
-				inlconv2expr(l->n);
+				inlconv2expr(&l->n);
 	}
 
 	inlnodelist(n->rlist);
@@ -377,13 +379,13 @@ inlnode(Node **np)
 	default:
 		for(l=n->rlist; l; l=l->next)
 			if(l->n->op == OINLCALL)
-				inlconv2expr(l->n);
+				inlconv2expr(&l->n);
 
 	}
 
 	inlnode(&n->ntest);
 	if(n->ntest && n->ntest->op == OINLCALL)
-		inlconv2expr(n->ntest);
+		inlconv2expr(&n->ntest);
 
 	inlnode(&n->nincr);
 	if(n->nincr && n->nincr->op == OINLCALL)
@@ -504,11 +506,14 @@ mkinlcall(Node **np, Node *fn)
 			fatal("missing inlvar for %N\n", t->nname);
 
 		if(n->left->op == ODOTMETH) {
-			if (!n->left->left)
+			if(!n->left->left)
 				fatal("method call without receiver: %+N", n);
-			if(t != T && t->nname != N && !isblank(t->nname))
+			if(t == T)
+				fatal("method call unknown receiver type: %+N", n);
+			if(t->nname != N && !isblank(t->nname))
 				as = nod(OAS, t->nname->inlvar, n->left->left);
-			// else if !ONAME add to init anyway?
+			else
+				as = nod(OAS, temp(t->type), n->left->left);
 		} else {  // non-method call to method
 			if (!n->list)
 				fatal("non-method call to method without first arg: %+N", n);

src/cmd/gc/order.c

+// Copyright 2012 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.
+
+// Rewrite tree to use separate statements to enforce
+// order of evaluation.  Makes walk easier, because it
+// can (after this runs) reorder at will within an expression.
+
+#include	<u.h>
+#include	<libc.h>
+#include	"go.h"
+
+static void	orderstmt(Node*, NodeList**);
+static void	orderstmtlist(NodeList*, NodeList**);
+static void	orderexpr(Node**, NodeList**);
+static void	orderexprlist(NodeList*, NodeList**);
+
+void
+order(Node *fn)
+{
+	NodeList *out;
+	
+	out = nil;
+	orderstmtlist(fn->nbody, &out);
+	fn->nbody = out;
+}
+
+static void
+orderstmtlist(NodeList *l, NodeList **out)
+{
+	for(; l; l=l->next)
+		orderstmt(l->n, out);
+}
+
+// Order the block of statements *l onto a new list,
+// and then replace *l with that list.
+static void
+orderblock(NodeList **l)
+{
+	NodeList *out;
+	
+	out = nil;
+	orderstmtlist(*l, &out);
+	*l = out;
+}
+
+// Order the side effects in *np and leave them as
+// the init list of the final *np.
+static void
+orderexprinplace(Node **np)
+{
+	Node *n;
+	NodeList *out;
+	
+	n = *np;
+	out = nil;
+	orderexpr(&n, &out);
+	addinit(&n, out);
+	*np = n;
+}
+
+// Like orderblock, but applied to a single statement.
+static void
+orderstmtinplace(Node **np)
+{
+	Node *n;
+	NodeList *out;
+
+	n = *np;
+	out = nil;
+	orderstmt(n, &out);
+	*np = liststmt(out);
+}
+
+// Move n's init list to *out.
+static void
+orderinit(Node *n, NodeList **out)
+{
+	*out = concat(*out, n->ninit);
+	n->ninit = nil;
+}
+
+// Is the list l actually just f() for a multi-value function?
+static int
+ismulticall(NodeList *l)
+{
+	Node *n;
+	
+	// one arg only
+	if(l == nil || l->next != nil)
+		return 0;
+	n = l->n;
+	
+	// must be call
+	switch(n->op) {
+	default:
+		return 0;
+	case OCALLFUNC:
+	case OCALLMETH:
+	case OCALLINTER:
+		break;
+	}
+	
+	// call must return multiple values
+	return n->left->type->outtuple > 1;
+}
+
+// n is a multi-value function call.  Add t1, t2, .. = n to out
+// and return the list t1, t2, ...
+static NodeList*
+copyret(Node *n, NodeList **out)
+{
+	Type *t;
+	Node *tmp, *as;
+	NodeList *l1, *l2;
+	Iter tl;
+	
+	if(n->type->etype != TSTRUCT || !n->type->funarg)
+		fatal("copyret %T %d", n->type, n->left->type->outtuple);
+
+	l1 = nil;
+	l2 = nil;
+	for(t=structfirst(&tl, &n->type); t; t=structnext(&tl)) {
+		tmp = temp(t->type);
+		l1 = list(l1, tmp);
+		l2 = list(l2, tmp);
+	}
+	
+	as = nod(OAS2, N, N);
+	as->list = l1;
+	as->rlist = list1(n);
+	typecheck(&as, Etop);
+	orderstmt(as, out);
+
+	return l2;
+}
+
+static void
+ordercallargs(NodeList **l, NodeList **out)
+{
+	if(ismulticall(*l)) {
+		// return f() where f() is multiple values.
+		*l = copyret((*l)->n, out);
+	} else {
+		orderexprlist(*l, out);
+	}
+}
+
+static void
+ordercall(Node *n, NodeList **out)
+{
+	orderexpr(&n->left, out);
+	ordercallargs(&n->list, out);
+}
+
+static void
+orderstmt(Node *n, NodeList **out)
+{
+	int lno;
+	NodeList *l;
+	Node *r;
+
+	if(n == N)
+		return;
+
+	lno = setlineno(n);
+	switch(n->op) {
+	default:
+		fatal("orderstmt %O", n->op);
+
+	case OAS2:
+	case OAS2DOTTYPE:
+	case OAS2MAPR:
+	case OAS:
+	case OASOP:
+	case OCLOSE:
+	case OCOPY:
+	case ODELETE:
+	case OPANIC:
+	case OPRINT:
+	case OPRINTN:
+	case ORECOVER:
+	case ORECV:
+	case OSEND:
+		orderinit(n, out);
+		orderexpr(&n->left, out);
+		orderexpr(&n->right, out);
+		orderexprlist(n->list, out);
+		orderexprlist(n->rlist, out);
+		*out = list(*out, n);
+		break;
+	
+	case OAS2FUNC:
+		// Special: avoid copy of func call n->rlist->n.
+		orderinit(n, out);
+		orderexprlist(n->list, out);
+		ordercall(n->rlist->n, out);
+		*out = list(*out, n);
+		break;
+
+	case OAS2RECV:
+		// Special: avoid copy of receive.
+		orderinit(n, out);
+		orderexprlist(n->list, out);
+		orderexpr(&n->rlist->n->left, out);  // arg to recv
+		*out = list(*out, n);
+		break;
+
+	case OBLOCK:
+	case OEMPTY:
+		// Special: does not save n onto out.
+		orderinit(n, out);
+		orderstmtlist(n->list, out);
+		break;
+
+	case OBREAK:
+	case OCONTINUE:
+	case ODCL:
+	case ODCLCONST:
+	case ODCLTYPE:
+	case OFALL:
+	case_OFALL:
+	case OGOTO:
+	case OLABEL:
+		// Special: n->left is not an expression; save as is.
+		orderinit(n, out);
+		*out = list(*out, n);
+		break;
+
+	case OCALLFUNC:
+	case OCALLINTER:
+	case OCALLMETH:
+		// Special: handle call arguments.
+		orderinit(n, out);
+		ordercall(n, out);
+		*out = list(*out, n);
+		break;
+
+	case ODEFER:
+	case OPROC:
+		// Special: order arguments to inner call but not call itself.
+		orderinit(n, out);
+		ordercall(n->left, out);
+		*out = list(*out, n);
+		break;
+
+	case OFOR:
+		orderinit(n, out);
+		orderexprinplace(&n->ntest);
+		orderstmtinplace(&n->nincr);
+		orderblock(&n->nbody);
+		*out = list(*out, n);
+		break;
+		
+	case OIF:
+		orderinit(n, out);
+		orderexprinplace(&n->ntest);
+		orderblock(&n->nbody);
+		orderblock(&n->nelse);
+		*out = list(*out, n);
+		break;
+
+	case ORANGE:
+		orderinit(n, out);
+		orderexpr(&n->right, out);
+		for(l=n->list; l; l=l->next)
+			orderexprinplace(&l->n);
+		orderblock(&n->nbody);
+		*out = list(*out, n);
+		break;
+
+	case ORETURN:
+		ordercallargs(&n->list, out);
+		*out = list(*out, n);
+		break;
+		
+	case OSELECT:
+		orderinit(n, out);
+		for(l=n->list; l; l=l->next) {
+			if(l->n->op != OXCASE)
+				fatal("order select case %O", l->n->op);
+			r = l->n->left;
+			if(r == nil)
+				continue;
+			switch(r->op) {
+			case OSELRECV:
+			case OSELRECV2:
+				orderexprinplace(&r->left);
+				orderexprinplace(&r->ntest);
+				orderexpr(&r->right->left, out);
+				break;
+			case OSEND:
+				orderexpr(&r->left, out);
+				orderexpr(&r->right, out);
+				break;
+			}
+		}
+		*out = list(*out, n);
+		break;
+
+	case OSWITCH:
+		orderinit(n, out);
+		orderexpr(&n->ntest, out);
+		for(l=n->list; l; l=l->next) {
+			if(l->n->op != OXCASE)
+				fatal("order switch case %O", l->n->op);
+			orderexpr(&l->n->left, &l->n->ninit);
+		}
+		*out = list(*out, n);
+		break;
+
+	case OXFALL:
+		yyerror("fallthrough statement out of place");
+		n->op = OFALL;
+		goto case_OFALL;
+	}
+	
+	lineno = lno;
+}
+
+static void
+orderexprlist(NodeList *l, NodeList **out)
+{
+	for(; l; l=l->next)
+		orderexpr(&l->n, out);
+}
+
+static void
+orderexpr(Node **np, NodeList **out)
+{
+	Node *n;
+	int lno;
+
+	n = *np;
+	if(n == N)
+		return;
+
+	lno = setlineno(n);
+	orderinit(n, out);
+
+	switch(n->op) {
+	default:
+		orderexpr(&n->left, out);
+		orderexpr(&n->right, out);
+		orderexprlist(n->list, out);
+		orderexprlist(n->rlist, out);
+		break;
+	
+	case OANDAND:
+	case OOROR:
+		orderexpr(&n->left, out);
+		orderexprinplace(&n->right);
+		break;
+	
+	case OCALLFUNC:
+	case OCALLMETH:
+	case OCALLINTER:
+		ordercall(n, out);
+		n = copyexpr(n, n->type, out);
+		break;
+
+	case ORECV:
+		n = copyexpr(n, n->type, out);
+		break;
+	}
+	
+	lineno = lno;
+
+	*np = n;
+}

src/cmd/gc/pgen.c

@@ -55,6 +55,10 @@ compile(Node *fn)
 		}
 	}
 	
+	order(curfn);
+	if(nerrors != 0)
+		goto ret;
+	
 	hasdefer = 0;
 	walk(curfn);
 	if(nerrors != 0)

src/cmd/gc/sinit.c

@@ -154,6 +154,10 @@ init2(Node *n, NodeList **out)
 {
 	if(n == N || n->initorder == InitDone)
 		return;
+
+	if(n->op == ONAME && n->ninit)
+		fatal("name %S with ninit: %+N\n", n->sym, n);
+
 	init1(n, out);
 	init2(n->left, out);
 	init2(n->right, out);

src/cmd/gc/subr.c

@@ -1957,7 +1957,7 @@ safeexpr(Node *n, NodeList **init)
 	return cheapexpr(n, init);
 }
 
-static Node*
+Node*
 copyexpr(Node *n, Type *t, NodeList **init)
 {
 	Node *a, *l;
@@ -3522,3 +3522,26 @@ strlit(char *s)
 	t->len = strlen(s);
 	return t;
 }
+
+void
+addinit(Node **np, NodeList *init)
+{
+	Node *n;
+	
+	if(init == nil)
+		return;
+
+	n = *np;
+	switch(n->op) {
+	case ONAME:
+	case OLITERAL:
+		// There may be multiple refs to this node;
+		// introduce OCONVNOP to hold init list.
+		n = nod(OCONVNOP, n, N);
+		n->type = n->left->type;
+		n->typecheck = 1;
+		*np = n;
+		break;
+	}
+	n->ninit = concat(init, n->ninit);
+}

src/cmd/gc/typecheck.c

@@ -1161,6 +1161,7 @@ reswitch:
 			yyerror("missing argument to make");
 			goto error;
 		}
+		n->list = nil;
 		l = args->n;
 		args = args->next;
 		typecheck(&l, Etype);

src/cmd/gc/walk.c

@@ -199,14 +199,12 @@ walkstmt(Node **np)
 	case OPANIC:
 	case OEMPTY:
 	case ORECOVER:
-		if(n->typecheck == 0) {
-			dump("missing typecheck:", n);
-			fatal("missing typecheck");
-		}
+		if(n->typecheck == 0)
+			fatal("missing typecheck: %+N", n);
 		init = n->ninit;
 		n->ninit = nil;
 		walkexpr(&n, &init);
-		n->ninit = concat(init, n->ninit);
+		addinit(&n, init);
 		break;
 
 	case OBREAK:
@@ -250,7 +248,7 @@ walkstmt(Node **np)
 			init = n->ntest->ninit;
 			n->ntest->ninit = nil;
 			walkexpr(&n->ntest, &init);
-			n->ntest->ninit = concat(init, n->ntest->ninit);
+			addinit(&n->ntest, init);
 		}
 		walkstmt(&n->nincr);
 		walkstmtlist(n->nbody);
@@ -332,6 +330,9 @@ walkstmt(Node **np)
 		break;
 	}
 
+	if(n->op == ONAME)
+		fatal("walkstmt ended up with name: %+N", n);
+	
 	*np = n;
 }
 
@@ -402,10 +403,8 @@ walkexpr(Node **np, NodeList **init)
 	if(debug['w'] > 1)
 		dump("walk-before", n);
 
-	if(n->typecheck != 1) {
-		dump("missed typecheck", n);
-		fatal("missed typecheck");
-	}
+	if(n->typecheck != 1)
+		fatal("missed typecheck: %+N\n", n);
 
 	switch(n->op) {
 	default:
@@ -481,7 +480,7 @@ walkexpr(Node **np, NodeList **init)
 		// save elsewhere and store on the eventual n->right.
 		ll = nil;
 		walkexpr(&n->right, &ll);
-		n->right->ninit = concat(n->right->ninit, ll);
+		addinit(&n->right, ll);
 		goto ret;
 
 	case OPRINT:
@@ -994,8 +993,10 @@ walkexpr(Node **np, NodeList **init)
 	case ONEW:
 		if(n->esc == EscNone && n->type->type->width < (1<<16)) {
 			r = temp(n->type->type);
-			*init = list(*init, nod(OAS, r, N));  // zero temp
-			r = nod(OADDR, r, N);
+			r = nod(OAS, r, N);  // zero temp
+			typecheck(&r, Etop);
+			*init = list(*init, r);
+			r = nod(OADDR, r->left, N);
 			typecheck(&r, Erv);
 			n = r;
 		} else {
@@ -1878,7 +1879,7 @@ reorder3save(Node **np, NodeList *all, NodeList *stop, NodeList **early)
 	
 	q = temp(n->type);
 	q = nod(OAS, q, n);
-	q->typecheck = 1;
+	typecheck(&q, Etop);
 	*early = list(*early, q);
 	*np = q->left;
 }

test/fixedbugs/bug401.go

-// $G $D/$F.go || echo "Bug398"
+// $G $D/$F.go && $L $F.$A && ./$A.out || echo "Bug401"
 
 // Copyright 2011 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.
 
 // Issue 2582
-package foo
+package main
+
+type T struct{}
 
-type T struct {}
 func (T) cplx() complex128 {
-	for false {}  // avoid inlining
-	return complex(1,0)
+	for false {
+	} // avoid inlining
+	return complex(1, 0)
+}
+
+func (T) cplx2() complex128 {
+	return complex(0, 1)
 }
 
 type I interface {
 	cplx() complex128
 }
 
-func f(e float32, t T) {
+func main() {
 
-    	_ = real(t.cplx())
+	var t T
+
+	if v := real(t.cplx()); v != 1 {
+		panic("not-inlined complex call failed")
+	}
 	_ = imag(t.cplx())
 
+	_ = real(t.cplx2())
+	if v := imag(t.cplx2()); v != 1 {
+		panic("potentially inlined complex call failed")
+	}
+
 	var i I
 	i = t
-    	_ = real(i.cplx())
+	if v := real(i.cplx()); v != 1 {
+		panic("potentially inlined complex call failed")
+	}
 	_ = imag(i.cplx())
 }

test/func8.go

+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2011 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 main
+
+var calledf int
+
+func f() int {
+	calledf++
+	return 0
+}
+
+func g() int {
+	return calledf
+}
+
+var xy string
+
+func x() bool {
+	for false {
+	} // no inlining
+	xy += "x"
+	return false
+}
+
+func y() string {
+	for false {
+	} // no inlining
+	xy += "y"
+	return "abc"
+}
+
+func main() {
+	if f() == g() {
+		println("wrong f,g order")
+	}
+
+	if x() == (y() == "abc") {
+		panic("wrong compare")
+	}
+	if xy != "xy" {
+		println("wrong x,y order")
+	}
+}

test/reorder2.go

+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2010 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.
+
+// derived from fixedbugs/bug294.go
+
+package main
+
+var log string
+
+type TT int
+
+func (t TT) a(s string) TT {
+	log += "a(" + s + ")"
+	return t
+}
+
+func (TT) b(s string) string {
+	log += "b(" + s + ")"
+	return s
+}
+
+type F func(s string) F
+
+func a(s string) F {
+	log += "a(" + s + ")"
+	return F(a)
+}
+
+func b(s string) string {
+	log += "b(" + s + ")"
+	return s
+}
+
+type I interface {
+	a(s string) I
+	b(s string) string
+}
+
+type T1 int
+
+func (t T1) a(s string) I {
+	log += "a(" + s + ")"
+	return t
+}
+
+func (T1) b(s string) string {
+	log += "b(" + s + ")"
+	return s
+}
+
+// f(g(), h()) where g is not inlinable but h is will have the same problem.
+// As will x := g() + h() (same conditions).
+// And g() <- h().
+func f(x, y string) {
+	log += "f(" + x + ", " + y + ")"
+}
+
+func ff(x, y string) {
+	for false {
+	} // prevent inl
+	log += "ff(" + x + ", " + y + ")"
+}
+
+func h(x string) string {
+	log += "h(" + x + ")"
+	return x
+}
+
+func g(x string) string {
+	for false {
+	} // prevent inl
+	log += "g(" + x + ")"
+	return x
+}
+
+func main() {
+	err := 0
+	var t TT
+	if a("1")("2")("3"); log != "a(1)a(2)a(3)" {
+		println("expecting a(1)a(2)a(3) , got ", log)
+		err++
+	}
+	log = ""
+
+	if t.a("1").a(t.b("2")); log != "a(1)b(2)a(2)" {
+		println("expecting a(1)b(2)a(2), got ", log)
+		err++
+	}
+	log = ""
+	if a("3")(b("4"))(b("5")); log != "a(3)b(4)a(4)b(5)a(5)" {
+		println("expecting a(3)b(4)a(4)b(5)a(5), got ", log)
+		err++
+	}
+	log = ""
+	var i I = T1(0)
+	if i.a("6").a(i.b("7")).a(i.b("8")).a(i.b("9")); log != "a(6)b(7)a(7)b(8)a(8)b(9)a(9)" {
+		println("expecting a(6)ba(7)ba(8)ba(9), got", log)
+		err++
+	}
+	log = ""
+
+	if s := t.a("1").b("3"); log != "a(1)b(3)" || s != "3" {
+		println("expecting a(1)b(3) and 3, got ", log, " and ", s)
+		err++
+	}
+	log = ""
+
+	if s := t.a("1").a(t.b("2")).b("3") + t.a("4").b("5"); log != "a(1)b(2)a(2)b(3)a(4)b(5)" || s != "35" {
+		println("expecting a(1)b(2)a(2)b(3)a(4)b(5) and 35, got ", log, " and ", s)
+		err++
+	}
+	log = ""
+
+	if s := t.a("4").b("5") + t.a("1").a(t.b("2")).b("3"); log != "a(4)b(5)a(1)b(2)a(2)b(3)" || s != "53" {
+		println("expecting a(4)b(5)a(1)b(2)a(2)b(3) and 35, got ", log, " and ", s)
+		err++
+	}
+	log = ""
+
+	if ff(g("1"), g("2")); log != "g(1)g(2)ff(1, 2)" {
+		println("expecting g(1)g(2)ff..., got ", log)
+		err++
+	}
+	log = ""
+
+	if ff(g("1"), h("2")); log != "g(1)h(2)ff(1, 2)" {
+		println("expecting g(1)h(2)ff..., got ", log)
+		err++
+	}
+	log = ""
+
+	if ff(h("1"), g("2")); log != "h(1)g(2)ff(1, 2)" {
+		println("expecting h(1)g(2)ff..., got ", log)
+		err++
+	}
+	log = ""
+
+	if ff(h("1"), h("2")); log != "h(1)h(2)ff(1, 2)" {
+		println("expecting h(1)h(2)ff..., got ", log)
+		err++
+	}
+	log = ""
+
+	if s := g("1") + g("2"); log != "g(1)g(2)" || s != "12" {
+		println("expecting g1g2 and 12, got ", log, " and ", s)
+		err++
+	}
+	log = ""
+
+	if s := g("1") + h("2"); log != "g(1)h(2)" || s != "12" {
+		println("expecting g1h2 and 12, got ", log, " and ", s)
+		err++
+	}
+	log = ""
+
+	if s := h("1") + g("2"); log != "h(1)g(2)" || s != "12" {
+		println("expecting h1g2 and 12, got ", log, " and ", s)
+		err++
+	}
+	log = ""
+
+	if s := h("1") + h("2"); log != "h(1)h(2)" || s != "12" {
+		println("expecting h1h2 and 12, got ", log, " and ", s)
+		err++
+	}
+	log = ""
+
+	if err > 0 {
+		panic("fail")
+	}
+}