* [PATCH] c++: local alias in typename in lambda [PR105518]
@ 2022-12-14 17:48 Patrick Palka
2022-12-15 14:50 ` Jason Merrill
0 siblings, 1 reply; 2+ messages in thread
From: Patrick Palka @ 2022-12-14 17:48 UTC (permalink / raw)
To: gcc-patches; +Cc: jason, Patrick Palka
We substitute the qualifying scope of a TYPENAME_TYPE directly using
tsubst_aggr_type (so that we can pass entering_scope=true) instead of
going through tsubst, which means we don't properly reuse typedefs
during this substitution. This ends up causing us to reject the below
testcase because we substitute the TYPENAME_TYPE impl::type as if it
were written without the typedef impl for A<t>, and thus we expect the
non-capturing lambda to capture t.
This patch fixes this by making tsubst_aggr_type delegate typedefs
to tsubst so that get properly reused, and then adjusting the result
appropriately if entering_scope is true. In passing, this refactors
tsubst_aggr_type into two functions, one that's intended to be called
directly and a more minimal one that's intended to be called only from
the RECORD/UNION/ENUMERAL_TYPE cases of tsubst (and contains only the
necessary bits for that call site).
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk? Patch generated with -w to suppress noisy whitespace changes.
PR c++/105518
gcc/cp/ChangeLog:
* pt.cc (tsubst_aggr_type): Handle typedefs by delegating to
tsubst and adjusting the result if entering_scope. Split out
the main part of the function into ...
(tsubst_aggr_type_1) ... here.
(tsubst): Use tsubst_aggr_type_1 instead of tsubst_aggr_type.
Handle TYPE_PTRMEMFUNC_P RECORD_TYPEs here instead of in
tsubst_aggr_type_1.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/lambda/lambda-alias1.C: New test.
---
gcc/cp/pt.cc | 58 ++++++++++++++-----
.../g++.dg/cpp0x/lambda/lambda-alias1.C | 23 ++++++++
2 files changed, 65 insertions(+), 16 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-alias1.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 81b7787fd3d..86862e56410 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -185,6 +185,7 @@ static tree tsubst_template_parms (tree, tree, tsubst_flags_t);
static void tsubst_each_template_parm_constraints (tree, tree, tsubst_flags_t);
tree most_specialized_partial_spec (tree, tsubst_flags_t);
static tree tsubst_aggr_type (tree, tree, tsubst_flags_t, tree, int);
+static tree tsubst_aggr_type_1 (tree, tree, tsubst_flags_t, tree, int);
static tree tsubst_arg_types (tree, tree, tree, tsubst_flags_t, tree);
static tree tsubst_function_type (tree, tree, tsubst_flags_t, tree);
static bool check_specialization_scope (void);
@@ -13845,23 +13846,49 @@ tsubst_aggr_type (tree t,
if (t == NULL_TREE)
return NULL_TREE;
- /* If T is an alias template specialization, we want to substitute that
- rather than strip it, especially if it's dependent_alias_template_spec_p.
- It should be OK not to handle entering_scope in this case, since
- DECL_CONTEXT will never be an alias template specialization. We only get
- here with an alias when tsubst calls us for TYPENAME_TYPE. */
- if (alias_template_specialization_p (t, nt_transparent))
- return tsubst (t, args, complain, in_decl);
+ /* Handle typedefs via tsubst so that they get reused. */
+ if (typedef_variant_p (t))
+ {
+ t = tsubst (t, args, complain, in_decl);
+ if (t == error_mark_node)
+ return error_mark_node;
+
+ /* The effect of entering_scope is that when substitution yields a
+ dependent specialization A<T>, lookup_template_class prefers to
+ return A's primary template type instead of the implicit instantiation.
+ So when entering_scope, we mirror this behavior by inspecting
+ TYPE_CANONICAL appropriately, taking advantage of the fact that
+ lookup_template_class links the two types by setting TYPE_CANONICAL of
+ the latter to the former. */
+ if (entering_scope
+ && CLASS_TYPE_P (t)
+ && dependent_type_p (t)
+ && TYPE_CANONICAL (t) == TREE_TYPE (TYPE_TI_TEMPLATE (t)))
+ t = TYPE_CANONICAL (t);
+ return t;
+ }
switch (TREE_CODE (t))
{
case RECORD_TYPE:
- if (TYPE_PTRMEMFUNC_P (t))
- return tsubst (TYPE_PTRMEMFUNC_FN_TYPE (t), args, complain, in_decl);
-
- /* Fall through. */
case ENUMERAL_TYPE:
case UNION_TYPE:
+ return tsubst_aggr_type_1 (t, args, complain, in_decl, entering_scope);
+
+ default:
+ return tsubst (t, args, complain, in_decl);
+ }
+}
+
+/* The part of tsubst_aggr_type that's shared with tsubst. */
+
+static tree
+tsubst_aggr_type_1 (tree t,
+ tree args,
+ tsubst_flags_t complain,
+ tree in_decl,
+ int entering_scope)
+{
if (TYPE_TEMPLATE_INFO (t) && uses_template_parms (t))
{
tree argvec;
@@ -13892,10 +13919,6 @@ tsubst_aggr_type (tree t,
else
/* This is not a template type, so there's nothing to do. */
return t;
-
- default:
- return tsubst (t, args, complain, in_decl);
- }
}
/* Map from a FUNCTION_DECL to a vec of default argument instantiations,
@@ -15812,9 +15835,12 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
switch (code)
{
case RECORD_TYPE:
+ if (TYPE_PTRMEMFUNC_P (t))
+ return tsubst (TYPE_PTRMEMFUNC_FN_TYPE (t), args, complain, in_decl);
+ /* Fall through. */
case UNION_TYPE:
case ENUMERAL_TYPE:
- return tsubst_aggr_type (t, args, complain, in_decl,
+ return tsubst_aggr_type_1 (t, args, complain, in_decl,
/*entering_scope=*/0);
case ERROR_MARK:
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-alias1.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-alias1.C
new file mode 100644
index 00000000000..4ac69935054
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-alias1.C
@@ -0,0 +1,23 @@
+// PR c++/105518
+// { dg-do compile { target c++11 } }
+
+struct integral_constant {
+ constexpr operator int() const { return 42; }
+};
+
+template<int N>
+struct A {
+ using type = A;
+ static constexpr int value = N;
+};
+
+template<class T>
+void f(T t) {
+ using impl = A<t>;
+ [] (int) {
+ typename impl::type a; // { dg-bogus "'t' is not captured" }
+ return a.value;
+ }(0);
+}
+
+template void f(integral_constant);
--
2.39.0.56.g57e2c6ebbe
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] c++: local alias in typename in lambda [PR105518]
2022-12-14 17:48 [PATCH] c++: local alias in typename in lambda [PR105518] Patrick Palka
@ 2022-12-15 14:50 ` Jason Merrill
0 siblings, 0 replies; 2+ messages in thread
From: Jason Merrill @ 2022-12-15 14:50 UTC (permalink / raw)
To: Patrick Palka, gcc-patches
On 12/14/22 12:48, Patrick Palka wrote:
> We substitute the qualifying scope of a TYPENAME_TYPE directly using
> tsubst_aggr_type (so that we can pass entering_scope=true) instead of
> going through tsubst, which means we don't properly reuse typedefs
> during this substitution. This ends up causing us to reject the below
> testcase because we substitute the TYPENAME_TYPE impl::type as if it
> were written without the typedef impl for A<t>, and thus we expect the
> non-capturing lambda to capture t.
>
> This patch fixes this by making tsubst_aggr_type delegate typedefs
> to tsubst so that get properly reused, and then adjusting the result
> appropriately if entering_scope is true. In passing, this refactors
> tsubst_aggr_type into two functions, one that's intended to be called
> directly and a more minimal one that's intended to be called only from
> the RECORD/UNION/ENUMERAL_TYPE cases of tsubst (and contains only the
> necessary bits for that call site).
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk? Patch generated with -w to suppress noisy whitespace changes.
OK.
> PR c++/105518
>
> gcc/cp/ChangeLog:
>
> * pt.cc (tsubst_aggr_type): Handle typedefs by delegating to
> tsubst and adjusting the result if entering_scope. Split out
> the main part of the function into ...
> (tsubst_aggr_type_1) ... here.
> (tsubst): Use tsubst_aggr_type_1 instead of tsubst_aggr_type.
> Handle TYPE_PTRMEMFUNC_P RECORD_TYPEs here instead of in
> tsubst_aggr_type_1.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp0x/lambda/lambda-alias1.C: New test.
> ---
> gcc/cp/pt.cc | 58 ++++++++++++++-----
> .../g++.dg/cpp0x/lambda/lambda-alias1.C | 23 ++++++++
> 2 files changed, 65 insertions(+), 16 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-alias1.C
>
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 81b7787fd3d..86862e56410 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -185,6 +185,7 @@ static tree tsubst_template_parms (tree, tree, tsubst_flags_t);
> static void tsubst_each_template_parm_constraints (tree, tree, tsubst_flags_t);
> tree most_specialized_partial_spec (tree, tsubst_flags_t);
> static tree tsubst_aggr_type (tree, tree, tsubst_flags_t, tree, int);
> +static tree tsubst_aggr_type_1 (tree, tree, tsubst_flags_t, tree, int);
> static tree tsubst_arg_types (tree, tree, tree, tsubst_flags_t, tree);
> static tree tsubst_function_type (tree, tree, tsubst_flags_t, tree);
> static bool check_specialization_scope (void);
> @@ -13845,23 +13846,49 @@ tsubst_aggr_type (tree t,
> if (t == NULL_TREE)
> return NULL_TREE;
>
> - /* If T is an alias template specialization, we want to substitute that
> - rather than strip it, especially if it's dependent_alias_template_spec_p.
> - It should be OK not to handle entering_scope in this case, since
> - DECL_CONTEXT will never be an alias template specialization. We only get
> - here with an alias when tsubst calls us for TYPENAME_TYPE. */
> - if (alias_template_specialization_p (t, nt_transparent))
> - return tsubst (t, args, complain, in_decl);
> + /* Handle typedefs via tsubst so that they get reused. */
> + if (typedef_variant_p (t))
> + {
> + t = tsubst (t, args, complain, in_decl);
> + if (t == error_mark_node)
> + return error_mark_node;
> +
> + /* The effect of entering_scope is that when substitution yields a
> + dependent specialization A<T>, lookup_template_class prefers to
> + return A's primary template type instead of the implicit instantiation.
> + So when entering_scope, we mirror this behavior by inspecting
> + TYPE_CANONICAL appropriately, taking advantage of the fact that
> + lookup_template_class links the two types by setting TYPE_CANONICAL of
> + the latter to the former. */
> + if (entering_scope
> + && CLASS_TYPE_P (t)
> + && dependent_type_p (t)
> + && TYPE_CANONICAL (t) == TREE_TYPE (TYPE_TI_TEMPLATE (t)))
> + t = TYPE_CANONICAL (t);
> + return t;
> + }
>
> switch (TREE_CODE (t))
> {
> case RECORD_TYPE:
> - if (TYPE_PTRMEMFUNC_P (t))
> - return tsubst (TYPE_PTRMEMFUNC_FN_TYPE (t), args, complain, in_decl);
> -
> - /* Fall through. */
> case ENUMERAL_TYPE:
> case UNION_TYPE:
> + return tsubst_aggr_type_1 (t, args, complain, in_decl, entering_scope);
> +
> + default:
> + return tsubst (t, args, complain, in_decl);
> + }
> +}
> +
> +/* The part of tsubst_aggr_type that's shared with tsubst. */
> +
> +static tree
> +tsubst_aggr_type_1 (tree t,
> + tree args,
> + tsubst_flags_t complain,
> + tree in_decl,
> + int entering_scope)
> +{
> if (TYPE_TEMPLATE_INFO (t) && uses_template_parms (t))
> {
> tree argvec;
> @@ -13892,10 +13919,6 @@ tsubst_aggr_type (tree t,
> else
> /* This is not a template type, so there's nothing to do. */
> return t;
> -
> - default:
> - return tsubst (t, args, complain, in_decl);
> - }
> }
>
> /* Map from a FUNCTION_DECL to a vec of default argument instantiations,
> @@ -15812,9 +15835,12 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> switch (code)
> {
> case RECORD_TYPE:
> + if (TYPE_PTRMEMFUNC_P (t))
> + return tsubst (TYPE_PTRMEMFUNC_FN_TYPE (t), args, complain, in_decl);
> + /* Fall through. */
> case UNION_TYPE:
> case ENUMERAL_TYPE:
> - return tsubst_aggr_type (t, args, complain, in_decl,
> + return tsubst_aggr_type_1 (t, args, complain, in_decl,
> /*entering_scope=*/0);
>
> case ERROR_MARK:
> diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-alias1.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-alias1.C
> new file mode 100644
> index 00000000000..4ac69935054
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-alias1.C
> @@ -0,0 +1,23 @@
> +// PR c++/105518
> +// { dg-do compile { target c++11 } }
> +
> +struct integral_constant {
> + constexpr operator int() const { return 42; }
> +};
> +
> +template<int N>
> +struct A {
> + using type = A;
> + static constexpr int value = N;
> +};
> +
> +template<class T>
> +void f(T t) {
> + using impl = A<t>;
> + [] (int) {
> + typename impl::type a; // { dg-bogus "'t' is not captured" }
> + return a.value;
> + }(0);
> +}
> +
> +template void f(integral_constant);
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