cmd/compile: fix comma-ok assignments for non-boolean ok

Passes toolstash -cmp.

Fixes #16870.

Change-Id: I70dc3bbb3cd3031826e5a54b96ba1ea603c282d1
Reviewed-on: https://go-review.googlesource.com/27910
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

src/cmd/compile/internal/gc/order.go

@@ -573,16 +573,29 @@ func orderstmt(n *Node, order *Order) {
 
 		orderexprlist(n.List, order)
 		n.Rlist.First().Left = orderexpr(n.Rlist.First().Left, order, nil) // i in i.(T)
-		if isblank(n.List.First()) {
-			order.out = append(order.out, n)
-		} else {
+
+		var tmp1, tmp2 *Node
+		if !isblank(n.List.First()) {
 			typ := n.Rlist.First().Type
-			tmp1 := ordertemp(typ, order, haspointers(typ))
-			order.out = append(order.out, n)
+			tmp1 = ordertemp(typ, order, haspointers(typ))
+		}
+		if !isblank(n.List.Second()) && !n.List.Second().Type.IsBoolean() {
+			tmp2 = ordertemp(Types[TBOOL], order, false)
+		}
+
+		order.out = append(order.out, n)
+
+		if tmp1 != nil {
 			r := Nod(OAS, n.List.First(), tmp1)
 			r = typecheck(r, Etop)
 			ordermapassign(r, order)
-			n.List.Set([]*Node{tmp1, n.List.Second()})
+			n.List.SetIndex(0, tmp1)
+		}
+		if tmp2 != nil {
+			r := okas(n.List.Second(), tmp2)
+			r = typecheck(r, Etop)
+			ordermapassign(r, order)
+			n.List.SetIndex(1, tmp2)
 		}
 
 		cleantemp(t, order)
@@ -596,17 +609,12 @@ func orderstmt(n *Node, order *Order) {
 		n.Rlist.First().Left = orderexpr(n.Rlist.First().Left, order, nil) // arg to recv
 		ch := n.Rlist.First().Left.Type
 		tmp1 := ordertemp(ch.Elem(), order, haspointers(ch.Elem()))
-		var tmp2 *Node
-		if !isblank(n.List.Second()) {
-			tmp2 = ordertemp(n.List.Second().Type, order, false)
-		} else {
-			tmp2 = ordertemp(Types[TBOOL], order, false)
-		}
+		tmp2 := ordertemp(Types[TBOOL], order, false)
 		order.out = append(order.out, n)
 		r := Nod(OAS, n.List.First(), tmp1)
 		r = typecheck(r, Etop)
 		ordermapassign(r, order)
-		r = Nod(OAS, n.List.Second(), tmp2)
+		r = okas(n.List.Second(), tmp2)
 		r = typecheck(r, Etop)
 		ordermapassign(r, order)
 		n.List.Set([]*Node{tmp1, tmp2})
@@ -882,8 +890,8 @@ func orderstmt(n *Node, order *Order) {
 							n2.Ninit.Append(tmp2)
 						}
 
-						r.List.Set1(ordertemp(tmp1.Type, order, false))
-						tmp2 = Nod(OAS, tmp1, r.List.First())
+						r.List.Set1(ordertemp(Types[TBOOL], order, false))
+						tmp2 = okas(tmp1, r.List.First())
 						tmp2 = typecheck(tmp2, Etop)
 						n2.Ninit.Append(tmp2)
 					}
@@ -1206,3 +1214,12 @@ func orderexpr(n *Node, order *Order, lhs *Node) *Node {
 	lineno = lno
 	return n
 }
+
+// okas creates and returns an assignment of val to ok,
+// including an explicit conversion if necessary.
+func okas(ok, val *Node) *Node {
+	if !isblank(ok) {
+		val = conv(val, ok.Type)
+	}
+	return Nod(OAS, ok, val)
+}

src/cmd/compile/internal/gc/walk.go

@@ -842,8 +842,9 @@ opswitch:
 		}
 		n1.Etype = 1 // addr does not escape
 		fn := chanfn("chanrecv2", 2, r.Left.Type)
-		r = mkcall1(fn, n.List.Second().Type, init, typename(r.Left.Type), r.Left, n1)
-		n = Nod(OAS, n.List.Second(), r)
+		ok := n.List.Second()
+		call := mkcall1(fn, ok.Type, init, typename(r.Left.Type), r.Left, n1)
+		n = Nod(OAS, ok, call)
 		n = typecheck(n, Etop)
 
 		// a,b = m[i];
@@ -898,8 +899,8 @@ opswitch:
 		// mapaccess2* returns a typed bool, but due to spec changes,
 		// the boolean result of i.(T) is now untyped so we make it the
 		// same type as the variable on the lhs.
-		if !isblank(n.List.Second()) {
-			r.Type.Field(1).Type = n.List.Second().Type
+		if ok := n.List.Second(); !isblank(ok) && ok.Type.IsBoolean() {
+			r.Type.Field(1).Type = ok.Type
 		}
 		n.Rlist.Set1(r)
 		n.Op = OAS2FUNC
@@ -933,6 +934,7 @@ opswitch:
 
 	case OAS2DOTTYPE:
 		e := n.Rlist.First() // i.(T)
+
 		// TODO(rsc): The Isfat is for consistency with componentgen and orderexpr.
 		// It needs to be removed in all three places.
 		// That would allow inlining x.(struct{*int}) the same as x.(*int).
@@ -957,6 +959,9 @@ opswitch:
 		if !isblank(ok) {
 			oktype = ok.Type
 		}
+		if !oktype.IsBoolean() {
+			Fatalf("orderstmt broken: got %L, want boolean", oktype)
+		}
 
 		fromKind := from.Type.iet()
 		toKind := t.iet()

test/fixedbugs/issue16870.go

@@ -0,0 +1,140 @@
+// run
+
+// Copyright 2016 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
+
+import (
+	"log"
+	"reflect"
+)
+
+func test(got, want interface{}) {
+	if !reflect.DeepEqual(got, want) {
+		log.Fatalf("got %v, want %v", got, want)
+	}
+}
+
+func main() {
+	var i int
+	var ip *int
+	var ok interface{}
+
+	// Channel receives.
+	c := make(chan int, 1)
+	c2 := make(chan int)
+
+	c <- 42
+	i, ok = <-c
+	test(i, 42)
+	test(ok, true)
+
+	c <- 42
+	_, ok = <-c
+	test(ok, true)
+
+	c <- 42
+	select {
+	case i, ok = <-c:
+		test(i, 42)
+		test(ok, true)
+	}
+
+	c <- 42
+	select {
+	case _, ok = <-c:
+		test(ok, true)
+	}
+
+	c <- 42
+	select {
+	case i, ok = <-c:
+		test(i, 42)
+		test(ok, true)
+	default:
+		log.Fatal("bad select")
+	}
+
+	c <- 42
+	select {
+	case _, ok = <-c:
+		test(ok, true)
+	default:
+		log.Fatal("bad select")
+	}
+
+	c <- 42
+	select {
+	case i, ok = <-c:
+		test(i, 42)
+		test(ok, true)
+	case <-c2:
+		log.Fatal("bad select")
+	}
+
+	c <- 42
+	select {
+	case _, ok = <-c:
+		test(ok, true)
+	case <-c2:
+		log.Fatal("bad select")
+	}
+
+	close(c)
+	i, ok = <-c
+	test(i, 0)
+	test(ok, false)
+
+	_, ok = <-c
+	test(ok, false)
+
+	// Map indexing.
+	m := make(map[int]int)
+
+	i, ok = m[0]
+	test(i, 0)
+	test(ok, false)
+
+	_, ok = m[0]
+	test(ok, false)
+
+	m[0] = 42
+	i, ok = m[0]
+	test(i, 42)
+	test(ok, true)
+
+	_, ok = m[0]
+	test(ok, true)
+
+	// Type assertions.
+	var u interface{}
+
+	i, ok = u.(int)
+	test(i, 0)
+	test(ok, false)
+
+	ip, ok = u.(*int)
+	test(ip, (*int)(nil))
+	test(ok, false)
+
+	_, ok = u.(int)
+	test(ok, false)
+
+	u = 42
+	i, ok = u.(int)
+	test(i, 42)
+	test(ok, true)
+
+	_, ok = u.(int)
+	test(ok, true)
+
+	u = &i
+	ip, ok = u.(*int)
+	test(ip, &i)
+	test(ok, true)
+
+	_, ok = u.(*int)
+	test(ok, true)
+}