The following (probably invalid) code snippet triggers an ICE on trunk (4.9.0 20130926) when compiled with "std=c++0x -flto":

====================
auto foo();

auto fp = foo;
====================

bug.cc:1:10: warning: 'foo' function uses 'auto' type specifier without trailing return type [enabled by default]
 auto foo();
          ^
bug.cc:3:14: internal compiler error: tree code 'template_type_parm' is not supported in LTO streams
 auto fp = foo;
              ^
0xa17696 DFS_write_tree
        ../../gcc/gcc/lto-streamer-out.c:1244
0xa165c9 DFS_write_tree_body
        ../../gcc/gcc/lto-streamer-out.c:461
0xa165c9 DFS_write_tree
        ../../gcc/gcc/lto-streamer-out.c:1152
0xa165c9 DFS_write_tree_body
        ../../gcc/gcc/lto-streamer-out.c:461
0xa165c9 DFS_write_tree
        ../../gcc/gcc/lto-streamer-out.c:1152
0xa18907 lto_output_tree(output_block*, tree_node*, bool, bool)
        ../../gcc/gcc/lto-streamer-out.c:1334
0xa12cfc write_global_stream
        ../../gcc/gcc/lto-streamer-out.c:2084
0xa1a990 lto_output_decl_state_streams
        ../../gcc/gcc/lto-streamer-out.c:2128
0xa1a990 produce_asm_for_decls
        ../../gcc/gcc/lto-streamer-out.c:2413
0xa4e720 ipa_write_summaries_2
        ../../gcc/gcc/passes.c:2283
0xa4f799 ipa_write_summaries_1
        ../../gcc/gcc/passes.c:2314
0xa4f799 ipa_write_summaries()
        ../../gcc/gcc/passes.c:2371
0x807c5b ipa_passes
        ../../gcc/gcc/cgraphunit.c:2019
0x807c5b compile()
        ../../gcc/gcc/cgraphunit.c:2115
0x807ee9 finalize_compilation_unit()
        ../../gcc/gcc/cgraphunit.c:2269
0x61b2b0 cp_write_global_declarations()
        ../../gcc/gcc/cp/decl2.c:4360
Please submit a full bug report, [etc.]


In GCC 4.8.1 the code was rejected:
bug.cc:1:10: warning: 'foo' function uses 'auto' type specifier without trailing return type [enabled by default]
 auto foo();
          ^
bug.cc:3:11: error: use of 'auto foo()' before deduction of 'auto'
 auto fp = foo;