On 4/28/20 11:55 PM, Marek Polacek wrote:
Whew, this took a while. We fail to parse "p->template A<T>::a()"
(where p is of type A<T> *) because since r249752 we treat the RHS of the ->
as dependent and avoid a lookup in the enclosing context: since that rev
cp_parser_template_name checks parser->context->object_type too, which
here is unknown_type_node, signalling a type-dependent object:
7756 if (dependent_p)
7757 /* Tell cp_parser_lookup_name that there was an object, even though
it's
7758 type-dependent. */
7759 parser->context->object_type = unknown_type_node;
with which cp_parser_template_name returns identifier 'A', cp_parser_class_name
then creates a TEMPLATE_ID_EXPR A<T>, but then
23735 decl = make_typename_type (scope, decl, tag_type, tf_error);
in cp_parser_class_name fails because scope is NULL. Then we return
error_mark_node and parse errors ensue.
I've tried various approaches, e.g. keeping TEMPLATE_ID_EXPR around
instead of calling make_typename_type, which didn't work, whereupon I
realized that since we don't want to perform name lookup if we've seen
the template keyword and the scope is dependent, we can adjust
parser->context->object_type and use the type of the object expression
as the scope, even if it's type-dependent. This should be in line with
[basic.lookup.classref]p4.
The "&& scope != unknown_type_node" line in cp_parser_class_name is there
for diagnostic purposes only (to avoid issuing a confusing error).
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
(Happy to defer to GCC 11 if this doesn't seem very safe.)
PR c++/94799
* parser.c (cp_parser_postfix_dot_deref_expression): If we have
a type-dependent object of class type, stash it to
parser->context->object_type.
(cp_parser_class_name): Consider object scope too. Don't call
make_typename_type when the scope is unknown_type_node.
* g++.dg/lookup/this1.C: Adjust dg-error.
* g++.dg/template/lookup12.C: New test.
* g++.dg/template/lookup13.C: New test.
* g++.dg/template/lookup14.C: New test.
---
gcc/cp/parser.c | 28 ++++++++++++++++++------
gcc/testsuite/g++.dg/lookup/this1.C | 2 +-
gcc/testsuite/g++.dg/template/lookup12.C | 26 ++++++++++++++++++++++
gcc/testsuite/g++.dg/template/lookup13.C | 28 ++++++++++++++++++++++++
gcc/testsuite/g++.dg/template/lookup14.C | 11 ++++++++++
5 files changed, 87 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/template/lookup12.C
create mode 100644 gcc/testsuite/g++.dg/template/lookup13.C
create mode 100644 gcc/testsuite/g++.dg/template/lookup14.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index e1f9786893a..b344721fb60 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -7694,11 +7694,16 @@ cp_parser_postfix_dot_deref_expression (cp_parser
*parser,
bool pseudo_destructor_p;
tree scope = NULL_TREE;
location_t start_loc = postfix_expression.get_start ();
+ tree type = TREE_TYPE (postfix_expression);
/* If this is a `->' operator, dereference the pointer. */
if (token_type == CPP_DEREF)
- postfix_expression = build_x_arrow (location, postfix_expression,
- tf_warning_or_error);
+ {
+ if (type && POINTER_TYPE_P (type))
+ type = TREE_TYPE (type);
+ postfix_expression = build_x_arrow (location, postfix_expression,
+ tf_warning_or_error);
+ }
/* Check to see whether or not the expression is type-dependent and
not the current instantiation. */
dependent_p = type_dependent_object_expression_p (postfix_expression);
@@ -7754,9 +7759,10 @@ cp_parser_postfix_dot_deref_expression (cp_parser
*parser,
}
if (dependent_p)
- /* Tell cp_parser_lookup_name that there was an object, even though it's
- type-dependent. */
- parser->context->object_type = unknown_type_node;
+ /* If we don't have a (type-dependent) object of class type, use
+ unknown_type_node to signal that there was an object. */
+ parser->context->object_type = (type && CLASS_TYPE_P (type)
+ ? type : unknown_type_node);
Anything that depends on CLASS_TYPE_P won't work if 'p' isn't clearly a
class, i.e. if it has type T*, T, or NULL_TREE. Why not use any
non-null type here?
For null type, I wonder if using decltype would make sense.
/* Assume this expression is not a pseudo-destructor access. */
pseudo_destructor_p = false;
@@ -23625,8 +23631,15 @@ cp_parser_class_name (cp_parser *parser,
}
/* PARSER->SCOPE can be cleared when parsing the template-arguments
- to a template-id, so we save it here. */
- scope = parser->scope;
+ to a template-id, so we save it here. Consider object scope too,
+ so that make_typename_type below can use it (cp_parser_template_name
+ considers object scope also). This may happen with code like
+
+ p->template A<T>::a()
+
+ where we first want to look up A<T>::a in the class of the object
+ expression, as per [basic.lookup.classref]. */
+ scope = parser->scope ? parser->scope : parser->context->object_type;
if (scope == error_mark_node)
return error_mark_node;
@@ -23720,6 +23733,7 @@ cp_parser_class_name (cp_parser *parser,
/* Check to see that it is really the name of a class. */
if (TREE_CODE (decl) == TEMPLATE_ID_EXPR
&& identifier_p (TREE_OPERAND (decl, 0))
+ && scope != unknown_type_node
This will make the more general dependent case give an error.
&& cp_lexer_next_token_is (parser->lexer, CPP_SCOPE))
/* Situations like this:
diff --git a/gcc/testsuite/g++.dg/lookup/this1.C b/gcc/testsuite/g++.dg/lookup/this1.C
index 20051bf7515..6b85cefcd37 100644
--- a/gcc/testsuite/g++.dg/lookup/this1.C
+++ b/gcc/testsuite/g++.dg/lookup/this1.C
@@ -4,5 +4,5 @@
struct A
{
template<int> static void foo();
- static void bar() { this->A::foo<0>(); } // { dg-error "unavailable" }
+ static void bar() { this->A::foo<0>(); } // { dg-error "unavailable|not a
class|expected" }
};
diff --git a/gcc/testsuite/g++.dg/template/lookup12.C
b/gcc/testsuite/g++.dg/template/lookup12.C
new file mode 100644
index 00000000000..fc5939ab0f6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/lookup12.C
@@ -0,0 +1,26 @@
+// PR c++/94799 - member template function lookup fails.
+
+template<typename T> struct B {
+ void foo ();
+ int i;
+};
+
+template<typename T>
+struct D : public B<T> { };
+
+template<typename T>
+void fn (D<T> d)
+{
+ d.template B<T>::foo ();
+ d.template B<T>::i = 42;
+ D<T>().template B<T>::foo ();
+ d.template D<T>::template B<T>::foo ();
+ d.template D<T>::template B<T>::i = 10;
+}
+
+int
+main ()
+{
+ D<int> d;
+ fn(d);
+}
diff --git a/gcc/testsuite/g++.dg/template/lookup13.C
b/gcc/testsuite/g++.dg/template/lookup13.C
new file mode 100644
index 00000000000..a8c7e18a707
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/lookup13.C
@@ -0,0 +1,28 @@
+// PR c++/94799 - member template function lookup fails.
+
+template <typename T>
+struct A {
+ int a() {
+ return 42;
+ }
+
+ template<typename> struct X { typedef int type; };
+};
+
+template <typename T>
+struct B {
+ int b(A<T> *p) {
+ int i = 0;
+ i += p->a();
+ i += p->template A<T>::a();
+ i += p->template A<T>::template A<T>::a();
+ i += A<T>().template A<T>::a();
+ return i;
+ }
+};
+
+int main() {
+ A<int> a;
+ B<int> b;
+ return b.b(&a);
+}
diff --git a/gcc/testsuite/g++.dg/template/lookup14.C
b/gcc/testsuite/g++.dg/template/lookup14.C
new file mode 100644
index 00000000000..e1c945a6dca
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/lookup14.C
@@ -0,0 +1,11 @@
+// PR c++/94799 - member template function lookup fails.
+
+template<typename T>
+struct A { };
+
+template<typename T>
+void fn (A<T> a)
+{
+ // Don't perform name lookup of foo when parsing this template.
+ a.template A<T>::foo ();
+}
base-commit: 19667c82e479dc2bf8351588ed57aff90220b748
