cmd/compile: return assignment mismatch error in var declarations

Some var declarations return "extra expression" or "missing expression"
errors when they should return “assignment mismatch” instead. Change
the returned error messages to exhibit the desired behavior.

Fixes #30085.

Change-Id: I7189355fbb0f976d70100779db4f81a9ae64fb11
Reviewed-on: https://go-review.googlesource.com/c/go/+/161558
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>

diff --git a/src/cmd/compile/internal/gc/dcl.go b/src/cmd/compile/internal/gc/dcl.go
index 9f25e5e15ba26f5afaea4b743dd5c67ca2d8ed12..12875e798eb9b4ce6e5dd51b32f529870fc85edc 100644 (file)
--- a/src/cmd/compile/internal/gc/dcl.go
+++ b/src/cmd/compile/internal/gc/dcl.go
@@ -166,11 +166,12 @@ func variter(vl []*Node, t *Node, el []*Node) []*Node {
                return append(init, as2)
        }
 
+       nel := len(el)
        for _, v := range vl {
                var e *Node
                if doexpr {
                        if len(el) == 0 {
-                               yyerror("missing expression in var declaration")
+                               yyerror("assignment mismatch: %d variables but %d values", len(vl), nel)
                                break
                        }
                        e = el[0]
@@ -194,7 +195,7 @@ func variter(vl []*Node, t *Node, el []*Node) []*Node {
        }
 
        if len(el) != 0 {
-               yyerror("extra expression in var declaration")
+               yyerror("assignment mismatch: %d variables but %d values", len(vl), nel)
        }
        return init
 }

diff --git a/test/fixedbugs/issue30085.go b/test/fixedbugs/issue30085.go
new file mode 100644 (file)
index 0000000..8223c85
--- /dev/null
+++ b/test/fixedbugs/issue30085.go
@@ -0,0 +1,12 @@
+// errorcheck
+
+// 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.
+
+package main
+
+func main() {
+       var c, d = 1, 2, 3 // ERROR "assignment mismatch: 2 variables but 3 values"
+       var e, f, g = 1, 2 // ERROR "assignment mismatch: 3 variables but 2 values"
+}