cmd/compile: only print one error for bad-type literal in assignment

ALTree · griesemer · commit 3218b1aa6fff · 2017-04-20T22:21:55.000Z
Fixes golang#8438 Change-Id: Ib43cdcdc962a8d9e14faf984bc859a92ba1eb517 Reviewed-on: https://go-review.googlesource.com/40531 Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/src/cmd/compile/internal/gc/subr.go b/src/cmd/compile/internal/gc/subr.go
@@ -982,7 +982,9 @@ func assignconvfn(n *Node, t *types.Type, context func() string) *Node {
 	var why string
 	op := assignop(n.Type, t, &why)
 	if op == 0 {
-		yyerror("cannot use %L as type %v in %s%s", n, t, context(), why)
+		if !old.Diag() {
+			yyerror("cannot use %L as type %v in %s%s", n, t, context(), why)
+		}
 		op = OCONV
 	}
 
diff --git a/test/fixedbugs/issue8438.go b/test/fixedbugs/issue8438.go
@@ -0,0 +1,17 @@
+// errorcheck
+
+// Copyright 2017 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 that we don't print duplicate errors for string ->
+// array-literal conversion
+
+package main
+
+func main() {
+	_ = []byte{"foo"}   // ERROR "cannot convert"
+	_ = []int{"foo"}    // ERROR "cannot convert"
+	_ = []rune{"foo"}   // ERROR "cannot convert"
+	_ = []string{"foo"} // OK
+}
diff --git a/test/interface/explicit.go b/test/interface/explicit.go
@@ -53,7 +53,7 @@ func main() {
 	i2 = I2(i) // ERROR "invalid|missing N method"
 
 	e = E(t) // ok
-	t = T(e) // ERROR "need explicit|need type assertion|incompatible" "as type [*]T"
+	t = T(e) // ERROR "need explicit|need type assertion|incompatible"
 }
 
 type M interface {
@@ -81,7 +81,6 @@ var m2 M = jj // ERROR "incompatible|wrong type for M method"
 var m3 = M(ii) // ERROR "invalid|missing"
 var m4 = M(jj) // ERROR "invalid|wrong type for M method"
 
-
 type B1 interface {
 	_() // ERROR "methods must have a unique non-blank name"
 }

Original file line number	Diff line number	Diff line change
`@@ -53,7 +53,7 @@ func main() {`
`53`	`53`	`i2 = I2(i) // ERROR "invalid\|missing N method"`
`54`	`54`
`55`	`55`	`e = E(t) // ok`
`56`		`- t = T(e) // ERROR "need explicit\|need type assertion\|incompatible" "as type [*]T"`
	`56`	`+ t = T(e) // ERROR "need explicit\|need type assertion\|incompatible"`
`57`	`57`	`}`
`58`	`58`
`59`	`59`	`type M interface {`
`@@ -81,7 +81,6 @@ var m2 M = jj // ERROR "incompatible\|wrong type for M method"`
`81`	`81`	`var m3 = M(ii) // ERROR "invalid\|missing"`
`82`	`82`	`var m4 = M(jj) // ERROR "invalid\|wrong type for M method"`
`83`	`83`
`84`		`-`
`85`	`84`	`type B1 interface {`
`86`	`85`	`_() // ERROR "methods must have a unique non-blank name"`
`87`	`86`	`}`