cmd/compile: fix export type conversion loss in inlined func body

Fixes #12677.

Change-Id: I72012f55615fcf5f4a16c054706c9bcd82e49ccd
Reviewed-on: https://go-review.googlesource.com/17817Reviewed-by: Ian Lance Taylor <iant@golang.org>

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

@@ -1120,7 +1120,7 @@ func exprfmt(n *Node, prec int) string {
 		if n.Val().Ctype() == CTNIL && n.Orig != nil && n.Orig != n {
 			return exprfmt(n.Orig, prec)
 		}
-		if n.Type != nil && n.Type != Types[n.Type.Etype] && n.Type != idealbool && n.Type != idealstring {
+		if n.Type != nil && n.Type.Etype != TIDEAL && n.Type.Etype != TNIL && n.Type != idealbool && n.Type != idealstring {
 			// Need parens when type begins with what might
 			// be misinterpreted as a unary operator: * or <-.
 			if Isptr[n.Type.Etype] || (n.Type.Etype == TCHAN && n.Type.Chan == Crecv) {

test/fixedbugs/issue12677.dir/p.go

+// Copyright 2015 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 p
+func Baz(f int) float64 {
+    return 1 / float64(int(1)<<(uint(f)))
+}

test/fixedbugs/issue12677.dir/q.go

+// Copyright 2015 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 q
+import "./p"
+func f() { println(p.Baz(2)) }

test/fixedbugs/issue12677.go

+// compiledir
+
+// Copyright 2015 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 12677: Type loss during export/import of inlined function body.
+
+package ignored