From 0e13dbc1a91cbe00e3c83a55f56db69380fe8f68 Mon Sep 17 00:00:00 2001 From: Josh Bleecher Snyder Date: Mon, 30 May 2016 16:42:38 -0700 Subject: [PATCH] cmd/compile: disallow multiple nil cases in a type switch Fixes #15898. Change-Id: I66e2ad21f283563c7142aa820f0354711d964768 Reviewed-on: https://go-review.googlesource.com/23573 Run-TryBot: Josh Bleecher Snyder Reviewed-by: Keith Randall --- src/cmd/compile/internal/gc/swt.go | 8 +++++++- test/fixedbugs/issue15898.go | 18 ++++++++++++++++++ 2 files changed, 25 insertions(+), 1 deletion(-) create mode 100644 test/fixedbugs/issue15898.go diff --git a/src/cmd/compile/internal/gc/swt.go b/src/cmd/compile/internal/gc/swt.go index aac92fd3114..4940c97a905 100644 --- a/src/cmd/compile/internal/gc/swt.go +++ b/src/cmd/compile/internal/gc/swt.go @@ -104,7 +104,7 @@ func typecheckswitch(n *Node) { n.Type = t - var def *Node + var def, niltype *Node for _, ncase := range n.List.Slice() { setlineno(n) if ncase.List.Len() == 0 { @@ -150,6 +150,12 @@ func typecheckswitch(n *Node) { var ptr int switch { case n1.Op == OLITERAL && n1.Type.IsKind(TNIL): + // case nil: + if niltype != nil { + Yyerror("multiple nil cases in type switch (first at %v)", niltype.Line()) + } else { + niltype = ncase + } case n1.Op != OTYPE && n1.Type != nil: // should this be ||? Yyerror("%v is not a type", Nconv(n1, FmtLong)) // reset to original type diff --git a/test/fixedbugs/issue15898.go b/test/fixedbugs/issue15898.go new file mode 100644 index 00000000000..7b66ea23dc6 --- /dev/null +++ b/test/fixedbugs/issue15898.go @@ -0,0 +1,18 @@ +// errorcheck + +// Copyright 2016 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(e interface{}) { + switch e.(type) { + case nil, nil: // ERROR "multiple nil cases in type switch" + } + + switch e.(type) { + case nil: + case nil: // ERROR "multiple nil cases in type switch" + } +}