cmd/compile: allow print/println(f()) where f() is multi-value

Fixes #35576

Change-Id: Ia128f412120069e9f8813e9e910e62644f950bfb
Reviewed-on: https://go-review.googlesource.com/c/go/+/207118
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -1805,7 +1805,7 @@ func typecheck1(n *Node, top int) (res *Node) {
 
 	case OPRINT, OPRINTN:
 		ok |= ctxStmt
-		typecheckslice(n.List.Slice(), ctxExpr)
+		typecheckargs(n)
 		ls := n.List.Slice()
 		for i1, n1 := range ls {
 			// Special case for print: int constant is int64, not int.

test/fixedbugs/issue35576.go

@@ -0,0 +1,16 @@
+// run
+
+// Copyright 2019 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.
+
+// Check print/println(f()) is allowed where f() is multi-value.
+
+package main
+
+func f() (int16, float64, string) { return -42, 42.0, "x" }
+
+func main() {
+	print(f())
+	println(f())
+}

test/fixedbugs/issue35576.out

@@ -0,0 +1 @@
+-42+4.200000e+001x-42 +4.200000e+001 x