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* [gcc r12-7101] c++: constrained auto in lambda using outer tparms [PR103706]
@ 2022-02-08 13:48 Patrick Palka
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From: Patrick Palka @ 2022-02-08 13:48 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:34ba3d9a2bf72742b1c150a2dd17d10e3e3f0964
commit r12-7101-g34ba3d9a2bf72742b1c150a2dd17d10e3e3f0964
Author: Patrick Palka <ppalka@redhat.com>
Date: Tue Feb 8 08:46:13 2022 -0500
c++: constrained auto in lambda using outer tparms [PR103706]
Here we're crashing during satisfaction of the lambda's placeholder type
constraints because the constraints depend on the template arguments
from the enclosing scope, which aren't part of the lambda's DECL_TI_ARGS.
This patch fixes this by making do_auto_deduction consider the
"regenerating" template arguments of a lambda for satisfaction,
mirroring what's done in satisfy_declaration_constraints.
PR c++/103706
gcc/cp/ChangeLog:
* constraint.cc (satisfy_declaration_constraints): Use
lambda_regenerating_args instead.
* cp-tree.h (lambda_regenerating_args): Declare.
* pt.cc (lambda_regenerating_args): Define, split out from
satisfy_declaration_constraints.
(do_auto_deduction): Use lambda_regenerating_args to obtain the
full set of outer template arguments for satisfaction when
inside a lambda.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-lambda18.C: New test.
Diff:
---
gcc/cp/constraint.cc | 7 ++---
gcc/cp/cp-tree.h | 1 +
gcc/cp/pt.cc | 39 ++++++++++++++++++++++----
gcc/testsuite/g++.dg/cpp2a/concepts-lambda18.C | 14 +++++++++
4 files changed, 51 insertions(+), 10 deletions(-)
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index cc4df4216ef..b7b9439f34b 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3154,12 +3154,11 @@ satisfy_declaration_constraints (tree t, sat_info info)
set of template arguments. Augment this with the outer template
arguments that were used to regenerate the lambda. */
gcc_assert (!args || TMPL_ARGS_DEPTH (args) == 1);
- tree lambda = CLASSTYPE_LAMBDA_EXPR (DECL_CONTEXT (t));
- tree outer_args = TI_ARGS (LAMBDA_EXPR_REGEN_INFO (lambda));
+ tree regen_args = lambda_regenerating_args (t);
if (args)
- args = add_to_template_args (outer_args, args);
+ args = add_to_template_args (regen_args, args);
else
- args = outer_args;
+ args = regen_args;
}
/* If any arguments depend on template parameters, we can't
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index d71be0a5bc7..f09055e4852 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7742,6 +7742,7 @@ extern void finish_lambda_scope (void);
extern tree start_lambda_function (tree fn, tree lambda_expr);
extern void finish_lambda_function (tree body);
extern bool regenerated_lambda_fn_p (tree);
+extern tree lambda_regenerating_args (tree);
extern tree most_general_lambda (tree);
extern tree finish_omp_target (location_t, tree, tree, bool);
extern void finish_omp_target_clauses (location_t, tree, tree *);
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c7af4712d8b..b58067d50e9 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -14446,6 +14446,21 @@ most_general_lambda (tree t)
return t;
}
+/* Return the set of template arguments used to regenerate the lambda T
+ from its most general lambda. */
+
+tree
+lambda_regenerating_args (tree t)
+{
+ if (LAMBDA_FUNCTION_P (t))
+ t = CLASSTYPE_LAMBDA_EXPR (DECL_CONTEXT (t));
+ gcc_assert (TREE_CODE (t) == LAMBDA_EXPR);
+ if (tree ti = LAMBDA_EXPR_REGEN_INFO (t))
+ return TI_ARGS (ti);
+ else
+ return NULL_TREE;
+}
+
/* We're instantiating a variable from template function TCTX. Return the
corresponding current enclosing scope. We can match them up using
DECL_SOURCE_LOCATION because lambdas only ever have one source location, and
@@ -30127,12 +30142,24 @@ do_auto_deduction (tree type, tree init, tree auto_node,
return type;
}
- if ((context == adc_return_type
- || context == adc_variable_type
- || context == adc_decomp_type)
- && current_function_decl
- && DECL_TEMPLATE_INFO (current_function_decl))
- outer_targs = DECL_TI_ARGS (current_function_decl);
+ if (context == adc_return_type
+ || context == adc_variable_type
+ || context == adc_decomp_type)
+ if (tree fn = current_function_decl)
+ if (DECL_TEMPLATE_INFO (fn) || LAMBDA_FUNCTION_P (fn))
+ {
+ outer_targs = DECL_TEMPLATE_INFO (fn)
+ ? DECL_TI_ARGS (fn) : NULL_TREE;
+ if (LAMBDA_FUNCTION_P (fn))
+ {
+ /* As in satisfy_declaration_constraints. */
+ tree regen_args = lambda_regenerating_args (fn);
+ if (outer_targs)
+ outer_targs = add_to_template_args (regen_args, outer_targs);
+ else
+ outer_targs = regen_args;
+ }
+ }
tree full_targs = add_to_template_args (outer_targs, targs);
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda18.C b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda18.C
new file mode 100644
index 00000000000..f1058daf317
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda18.C
@@ -0,0 +1,14 @@
+// PR c++/103706
+// { dg-do compile { target c++20 } }
+
+template<class T, class U> concept C = __is_same(U, int);
+
+template<class T> void f() {
+ []() -> C<T> auto {
+ C<T> auto x = T(); // { dg-error "constraints" }
+ return T(); // { dg-error "constraints" }
+ }();
+}
+
+template void f<int>(); // { dg-bogus "" }
+template void f<char>(); // { dg-message "required from here" }
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