cmd/compile: make error message involving variadic calls clearer

Fixes #41440

Change-Id: I2fbac72ae3b76bca32cdeaee678a19af3595d116
Reviewed-on: https://go-review.googlesource.com/c/go/+/255241
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index cbfaa3073e63162ddd84b6cc8d9427252a8e28d2..2654177c25bab3096dbec2889e7d66715e31de83 100644 (file)
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -2717,7 +2717,7 @@ func errorDetails(nl Nodes, tstruct *types.Type, isddd bool) string {
 // sigrepr is a type's representation to the outside world,
 // in string representations of return signatures
 // e.g in error messages about wrong arguments to return.
-func sigrepr(t *types.Type) string {
+func sigrepr(t *types.Type, isddd bool) string {
        switch t {
        case types.Idealstring:
                return "string"
@@ -2732,6 +2732,13 @@ func sigrepr(t *types.Type) string {
                return "number"
        }
 
+       // Turn []T... argument to ...T for clearer error message.
+       if isddd {
+               if !t.IsSlice() {
+                       Fatalf("bad type for ... argument: %v", t)
+               }
+               return "..." + t.Elem().String()
+       }
        return t.String()
 }
 
@@ -2742,15 +2749,12 @@ func (nl Nodes) sigerr(isddd bool) string {
        }
 
        var typeStrings []string
-       for _, n := range nl.Slice() {
-               typeStrings = append(typeStrings, sigrepr(n.Type))
+       for i, n := range nl.Slice() {
+               isdddArg := isddd && i == nl.Len()-1
+               typeStrings = append(typeStrings, sigrepr(n.Type, isdddArg))
        }
 
-       ddd := ""
-       if isddd {
-               ddd = "..."
-       }
-       return fmt.Sprintf("(%s%s)", strings.Join(typeStrings, ", "), ddd)
+       return fmt.Sprintf("(%s)", strings.Join(typeStrings, ", "))
 }
 
 // type check composite

diff --git a/test/fixedbugs/issue41440.go b/test/fixedbugs/issue41440.go
new file mode 100644 (file)
index 0000000..2b441db
--- /dev/null
+++ b/test/fixedbugs/issue41440.go
@@ -0,0 +1,14 @@
+// errorcheck
+
+// Copyright 2020 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 f(...int) {}
+
+func g() {
+       var x []int
+       f(x, x...) // ERROR "have \(\[\]int, \.\.\.int\)"
+}

diff --git a/test/fixedbugs/issue6750.go b/test/fixedbugs/issue6750.go
index dbbb454435df396650e1937343b5b235da1a2556..f62a85009c0fbb396bc6d818cb06094ced453543 100644 (file)
--- a/test/fixedbugs/issue6750.go
+++ b/test/fixedbugs/issue6750.go
@@ -18,5 +18,5 @@ func printmany(nums ...int) {
 func main() {
        printmany(1, 2, 3)
        printmany([]int{1, 2, 3}...)
-       printmany(1, "abc", []int{2, 3}...) // ERROR "too many arguments in call to printmany\n\thave \(number, string, \[\]int\.\.\.\)\n\twant \(...int\)"
+       printmany(1, "abc", []int{2, 3}...) // ERROR "too many arguments in call to printmany\n\thave \(number, string, \.\.\.int\)\n\twant \(...int\)"
 }