go.tools/go/types: comma-ok expressions return bool rather than untyped bool

Per the current spec.

Fixes golang/go#8188.

LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/101200043

go/ssa/interp/testdata/coverage.go

@@ -597,10 +597,21 @@ func init() {
 		// select to a simple receive statement.
 	}
 
+	// TODO(adonovan, gri) enable again once we accept issue 8189.
 	// value,ok-form receive where TypeOf(ok) is a named boolean.
-	type mybool bool
+	// type mybool bool
+	// var x int
+	// var y mybool
+	// select {
+	// case x, y = <-ch:
+	// default:
+	// 	// The default case disables the simplification of
+	// 	// select to a simple receive statement.
+	// }
+
+	// TODO(adonovan, gri) remove once we accept issue 8189.
 	var x int
-	var y mybool
+	var y bool
 	select {
 	case x, y = <-ch:
 	default:

go/types/api_test.go

@@ -167,9 +167,15 @@ func TestTypesInfo(t *testing.T) {
 			`x.(int)`,
 			`(int, bool)`,
 		},
-		{`package p2; type mybool bool; var m map[string]complex128; var b mybool; func _() { _, b = m["foo"] }`,
+		// TODO(gri): uncomment if we accept issue 8189.
+		// {`package p2; type mybool bool; var m map[string]complex128; var b mybool; func _() { _, b = m["foo"] }`,
+		// 	`m["foo"]`,
+		// 	`(complex128, p2.mybool)`,
+		// },
+		// TODO(gri): remove if we accept issue 8189.
+		{`package p2; var m map[string]complex128; var b bool; func _() { _, b = m["foo"] }`,
 			`m["foo"]`,
-			`(complex128, p2.mybool)`,
+			`(complex128, bool)`,
 		},
 		{`package p3; var c chan string; var _, _ = <-c`,
 			`<-c`,

go/types/call.go

@@ -140,7 +140,7 @@ func unpack(get getter, n int, allowCommaOk bool) (getter, int, bool) {
 		if x0.mode == mapindex || x0.mode == commaok {
 			// comma-ok value
 			if allowCommaOk {
-				a := [2]Type{x0.typ, Typ[UntypedBool]}
+				a := [2]Type{x0.typ, Typ[Bool]}
 				return func(x *operand, i int) {
 					x.mode = value
 					x.expr = x0.expr

go/types/testdata/expr0.src

@@ -6,6 +6,8 @@
 
 package expr0 
 
+type mybool bool
+
 var (
 	// bool
 	b0 = true
@@ -133,6 +135,10 @@ var (
 	ch7 = <-ch
 	ch8 = <-rc
 	ch9 = <-sc /* ERROR "cannot receive" */
+	ch10, ok = <-ch
+	// ok is of type bool
+	ch11, myok = <-ch
+	_ mybool = myok /* ERROR "cannot initialize" */
 )
 
 // address of composite literals

go/types/testdata/expr3.src

@@ -91,6 +91,17 @@ func indexes() {
 	_ = s[10:0:0] /* ERROR "invalid slice indices" */
 	_ = &s /* ERROR "cannot take address" */ [:10]
 
+	var m map[string]int
+	_ = m[0 /* ERROR "cannot convert" */ ]
+	_ = m /* ERROR "cannot slice" */ ["foo" : "bar"]
+	_ = m["foo"]
+	// ok is of type bool
+	type mybool bool
+	var ok mybool
+	_, ok = m /* ERROR "cannot assign" */ ["bar"]
+	_ = ok
+
+
 	var t string
 	_ = t[- /* ERROR "negative" */ 1]
 	_ = t[- /* ERROR "negative" */ 1 :]
@@ -348,6 +359,8 @@ type T2 struct{}
 
 func (T2) m(int) {}
 
+type mybool bool
+
 func type_asserts() {
 	var x int
 	_ = x /* ERROR "not an interface" */ .(int)
@@ -357,6 +370,11 @@ func type_asserts() {
 	x, ok = e.(int)
 	_ = ok
 
+	// ok value is of type bool
+	var myok mybool
+	_, myok = e /* ERROR "cannot assign" */ .(int)
+	_ = myok
+
 	var t I
 	_ = t /* ERROR "use of .* outside type switch" */ .(type)
 	_ = t /* ERROR "missing method m" */ .(T)