[RFC] c++: parse trivial DMI immediately [PR96645]
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Commit Message
This issue came up again the other day in conversation with another committee
member, and it occurred to me that although I don't have a complete solution to
this issue, I could push this patch I wrote a while back to fix trivial cases.
Do people think this would be desirable?
-- 8< --
The current direction of CWG2335 is to parse complete-class contexts as
needed rather than always wait until the end of the outermost class.
This doesn't fully implement that (nor fully fix PR96645), but takes a step
in that direction by allowing simple cases that do no name lookup; then
being in complete class scope makes no difference.
PR c++/96645
gcc/cp/ChangeLog:
* parser.cc (cp_parser_early_parsing_nsdmi): New.
(cp_parser_member_declaration): Call it.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/nsdmi10.C: Now OK.
* g++.dg/ext/is_constructible7.C: Likewise.
---
gcc/cp/parser.cc | 28 +++++++++++++++++++-
gcc/testsuite/g++.dg/cpp0x/nsdmi10.C | 4 +--
gcc/testsuite/g++.dg/ext/is_constructible7.C | 27 +++++++++++++++++++
3 files changed, 56 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/ext/is_constructible7.C
base-commit: ddf645c09461c6ebf444f27ebbcad8141f0dba56
@@ -3108,6 +3108,8 @@ static tree cp_parser_late_parse_one_default_arg
(cp_parser *, tree, tree, tree);
static void cp_parser_late_parsing_nsdmi
(cp_parser *, tree);
+static bool cp_parser_early_parsing_nsdmi
+ (cp_parser *, tree);
static void cp_parser_late_parsing_default_args
(cp_parser *, tree);
static tree cp_parser_sizeof_operand
@@ -31744,7 +31746,8 @@ cp_parser_member_declaration (cp_parser* parser)
if (DECL_DECLARES_FUNCTION_P (decl))
cp_parser_save_default_args (parser, STRIP_TEMPLATE (decl));
else if (TREE_CODE (decl) == FIELD_DECL
- && DECL_INITIAL (decl))
+ && DECL_INITIAL (decl)
+ && !cp_parser_early_parsing_nsdmi (parser, decl))
/* Add DECL to the queue of NSDMI to be parsed later. */
vec_safe_push (unparsed_nsdmis, decl);
}
@@ -37278,6 +37281,29 @@ cp_parser_late_parsing_nsdmi (cp_parser *parser, tree field)
DECL_INITIAL (field) = def;
}
+/* If the DEFERRED_PARSE for FIELD is safe to parse immediately, do so.
+ Returns true if deferred parsing is no longer needed. */
+
+static bool
+cp_parser_early_parsing_nsdmi (cp_parser *parser, tree field)
+{
+ tree init = DECL_INITIAL (field);
+ if (TREE_CODE (init) != DEFERRED_PARSE)
+ return true;
+
+ cp_token_cache *tokens = DEFPARSE_TOKENS (init);
+ for (cp_token *p = tokens->first; p != tokens->last; ++p)
+ if (p->type == CPP_NAME
+ || p->keyword == RID_THIS
+ || p->keyword == RID_OPERATOR)
+ /* There's a name to look up or 'this', give up. */
+ return false;
+
+ /* It's trivial, parse now. */
+ cp_parser_late_parsing_nsdmi (parser, field);
+ return true;
+}
+
/* FN is a FUNCTION_DECL which may contains a parameter with an
unparsed DEFERRED_PARSE. Parse the default args now. This function
assumes that the current scope is the scope in which the default
@@ -6,7 +6,7 @@ struct A1 {
int y1 = 1;
};
- A1(const B1& opts = B1()) {} // { dg-error "default member initializer" }
+ A1(const B1& opts = B1()) {}
};
struct A2 {
@@ -14,5 +14,5 @@ struct A2 {
int x2, y2 = 1;
};
- A2(const B2& opts = B2()) {} // { dg-error "default member initializer" }
+ A2(const B2& opts = B2()) {}
};
new file mode 100644
@@ -0,0 +1,27 @@
+// PR c++/96645
+// { dg-do compile { target c++11 } }
+
+template<bool B>
+struct bool_constant
+{
+ static constexpr bool value = B;
+ using type = bool_constant;
+};
+
+using true_type = bool_constant<true>;
+
+template<typename T>
+struct is_default_constructible
+ : bool_constant<__is_constructible(T)>
+{ };
+
+void testVarStruct()
+{
+ struct DataWithStruct {
+ struct A {
+ int number = 5; // compiles, if remove initialization
+ };
+
+ is_default_constructible<A>::type t = true_type{};
+ };
+}