[C++ Patch] PR 67369 ("[5/6 Regression] ICE (in tsubst_decl, at cp/pt.c:11302) with -std=c++14")

[Paolo Carlini]

Hi,

in this regression, an ICE is triggered in tsubst_decl, [case 
FUNCTION_DECL] at:

    /* Nobody should be tsubst'ing into non-template functions.  */
    gcc_assert (DECL_TEMPLATE_INFO (t) != NULL_TREE);

indeed, 't' is just the 'main' function. A simple way to avoid it is 
tweaking the code recently changed in tsubst_copy, [case FUNCTION_DECL] 
which calls tsubt_decl via tsusbt, to the effect of not calling the 
latter at all when DECL_CONTEXT (t) isn't a template.

Tested x86_64-linux.

Thanks,
Paolo.

/////////////////
/cp
2015-09-08  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/67369
        * pt.c (tsubst_copy, [case FUNCTION_DECL]): Do not call tsubst
        if the first argument isn't a template.

/testsuite
2015-09-08  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/67369
        * g++.dg/cpp1y/lambda-generic-ice4.C: New.
Index: cp/pt.c
===================================================================
--- cp/pt.c     (revision 227528)
+++ cp/pt.c     (working copy)
@@ -13599,8 +13599,9 @@ tsubst_copy (tree t, tree args, tsubst_flags_t com
              if (r)
                {
                  /* Make sure that the one we found is the one we want.  */
-                 tree ctx = tsubst (DECL_CONTEXT (t), args,
-                                    complain, in_decl);
+                 tree ctx = DECL_CONTEXT (t);
+                 if (DECL_LANG_SPECIFIC (ctx) && DECL_TEMPLATE_INFO (ctx))
+                   ctx = tsubst (ctx, args, complain, in_decl);
                  if (ctx != DECL_CONTEXT (r))
                    r = NULL_TREE;
                }
Index: testsuite/g++.dg/cpp1y/lambda-generic-ice4.C
===================================================================
--- testsuite/g++.dg/cpp1y/lambda-generic-ice4.C        (revision 0)
+++ testsuite/g++.dg/cpp1y/lambda-generic-ice4.C        (working copy)
@@ -0,0 +1,10 @@
+// PR c++/67369
+// { dg-do compile { target c++14 } }
+
+int main() {
+  unsigned const nsz = 0;
+  auto repeat_conditional = [&](auto) {
+    auto new_sz = nsz;
+  };
+  repeat_conditional(1);
+}