commit 70cf67704699c8bcaf6f52437812367cdc4ad169
author Cherry Zhang <cherryyz@google.com> Mon Sep 11 13:51:45 2017 -0400
committer Ian Lance Taylor <iant@golang.org> Fri Sep 15 21:24:39 2017 +0000
tree da84f5dfe309879d8327fee5620e3fb550184a4e
parent de7b370901c4fc6852eaa7372282bb699429ec4a

compiler: call error_statement for fallthrough in last case

It is possible to do this check in backend, by walking the
block and check whether the last statement is a goto. But it
seems easier to do it in the frontend, where it can simply use
is_fallthrough.

Change-Id: Icd61c52c96a408f7e00566cb7b232848cd449e25
Reviewed-on: https://go-review.googlesource.com/63690
Reviewed-by: Ian Lance Taylor <iant@golang.org>

go/statements.cc

diff --git a/go/statements.cc b/go/statements.cc
index eb370f8..bea57cd 100644
--- a/go/statements.cc
+++ b/go/statements.cc
@@ -3707,6 +3707,12 @@
       std::vector<Bexpression*> cases;
       Bstatement* stat = p->get_backend(context, break_label, &case_constants,
 					&cases);
+      // The final clause can't fall through.
+      if (i == c - 1 && p->is_fallthrough())
+        {
+          go_assert(saw_errors());
+          stat = context->backend()->error_statement();
+        }
       (*all_cases)[i].swap(cases);
       (*all_statements)[i] = stat;
     }