The following patch adds a fix-it insertion hint for missing "template <> " in explicit specializations.
This is more of an enhancement than a bug fix (PR 62314 is more of a catch-all for adding fix-its), but it's low-risk and a user-visible improvement, and this specific example is called out as a benefit of clang over gcc in: http://clang.llvm.org/diagnostics.html I note that clang suggests inserting template<> whereas our diagnostic talks about template <> hence I have the fixit suggest inserting that. Should we change our wording instead, and lose the space? Successfully bootstrapped®rtested on x86_64-pc-linux-gnu; adds 9 new PASS results to g++.sum. OK for trunk in stage 3? gcc/cp/ChangeLog: PR c++/62314 * parser.c (cp_parser_class_head): Capture the start location; use it to emit a fix-it insertion hint when complaining about missing "template <> " in explicit specializations. gcc/testsuite/ChangeLog: PR c++/62314 * g++.dg/pr62314.C: New test case. --- gcc/cp/parser.c | 18 ++++++++++++++++-- gcc/testsuite/g++.dg/pr62314.C | 17 +++++++++++++++++ 2 files changed, 33 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/pr62314.C diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c index a420cf1..2a688b2 100644 --- a/gcc/cp/parser.c +++ b/gcc/cp/parser.c @@ -21502,6 +21502,8 @@ cp_parser_class_head (cp_parser* parser, if (class_key == none_type) return error_mark_node; + location_t class_head_start_location = input_location; + /* Parse the attributes. */ attributes = cp_parser_attributes_opt (parser); @@ -21718,8 +21720,20 @@ cp_parser_class_head (cp_parser* parser, && parser->num_template_parameter_lists == 0 && template_id_p) { - error_at (type_start_token->location, - "an explicit specialization must be preceded by %<template <>%>"); + /* Build a location of this form: + struct typename <ARGS> + ^~~~~~~~~~~~~~~~~~~~~~ + with caret==start at the start token, and + finishing at the end of the type. */ + location_t reported_loc + = make_location (class_head_start_location, + class_head_start_location, + get_finish (type_start_token->location)); + rich_location richloc (line_table, reported_loc); + richloc.add_fixit_insert (class_head_start_location, "template <> "); + error_at_rich_loc + (&richloc, + "an explicit specialization must be preceded by %<template <>%>"); invalid_explicit_specialization_p = true; /* Take the same action that would have been taken by cp_parser_explicit_specialization. */ diff --git a/gcc/testsuite/g++.dg/pr62314.C b/gcc/testsuite/g++.dg/pr62314.C new file mode 100644 index 0000000..ebe75ec --- /dev/null +++ b/gcc/testsuite/g++.dg/pr62314.C @@ -0,0 +1,17 @@ +// { dg-options "-fdiagnostics-show-caret" } + +template <typename T> +struct iterator_traits {}; + +struct file_iterator; + +struct iterator_traits<file_iterator> { // { dg-error "explicit specialization must be preceded by .template" } +}; + +/* Verify that we emit a fixit hint for this case. */ + +/* { dg-begin-multiline-output "" } + struct iterator_traits<file_iterator> + ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + template <> + { dg-end-multiline-output "" } */ -- 1.8.5.3
