c++/modules: Ensure type of partial spec VAR_DECL is consistent with its template...

We were erroring because the TEMPLATE_DECL of the existing partial
specialisation has an undeduced return type, but the imported
declaration did not.

The root cause is similar to what was fixed in r13-2744-g4fac53d6522189,
where modules streaming code assumes that a TEMPLATE_DECL and its
DECL_TEMPLATE_RESULT will always have the same TREE_TYPE.  That commit
fixed the issue by ensuring that when the type of a variable is deduced
the TEMPLATE_DECL is updated as well, but missed handling partial
specialisations.  This patch ensures that the same adjustment is made
there as well.

	PR c++/120644

gcc/cp/ChangeLog:

	* decl.cc (cp_finish_decl): Also propagate type to partial
	templates.
	* module.cc (trees_out::decl_value): Add assertion that the
	TREE_TYPE of a streamed template decl matches its inner.
	(trees_in::is_matching_decl): Clarify function return type
	deduction should only occur for non-TEMPLATE_DECL.
	* pt.cc (template_for_substitution): Handle partial specs.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/auto-7.h: New test.
	* g++.dg/modules/auto-7_a.H: New test.
	* g++.dg/modules/auto-7_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>
Reviewed-by: Patrick Palka <ppalka@redhat.com>

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 4fe97ffbf8f9d01145a49e69e6e0a12239cb5332..83c8e283b56a930d77c9ce949318ec7f75923852 100644 (file)
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -8923,10 +8923,12 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
       cp_apply_type_quals_to_decl (cp_type_quals (type), decl);
 
       /* Update the type of the corresponding TEMPLATE_DECL to match.  */
-      if (DECL_LANG_SPECIFIC (decl)
-         && DECL_TEMPLATE_INFO (decl)
-         && DECL_TEMPLATE_RESULT (DECL_TI_TEMPLATE (decl)) == decl)
-       TREE_TYPE (DECL_TI_TEMPLATE (decl)) = type;
+      if (DECL_LANG_SPECIFIC (decl) && DECL_TEMPLATE_INFO (decl))
+       {
+         tree tmpl = template_for_substitution (decl);
+         if (DECL_TEMPLATE_RESULT (tmpl) == decl)
+           TREE_TYPE (tmpl) = type;
+       }
     }
 
   if (ensure_literal_type_for_constexpr_object (decl) == error_mark_node)

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 42a1b83e164396de1a32c2e8d82a20dbb502ad4d..846e532c4380a3ec11f83eb637a089de27d4135e 100644 (file)
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -8213,6 +8213,10 @@ trees_out::decl_value (tree decl, depset *dep)
       inner = DECL_TEMPLATE_RESULT (decl);
       inner_tag = insert (inner, WK_value);
 
+      /* On stream-in we assume that a template and its result will
+        have the same type.  */
+      gcc_checking_assert (TREE_TYPE (decl) == TREE_TYPE (inner));
+
       if (streaming_p ())
        {
          int code = TREE_CODE (inner);
@@ -12325,7 +12329,8 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
        {
          dump (dumper::MERGE)
            && dump ("Propagating deduced return type to %N", existing);
-         FNDECL_USED_AUTO (e_inner) = true;
+         gcc_checking_assert (existing == e_inner);
+         FNDECL_USED_AUTO (existing) = true;
          DECL_SAVED_AUTO_RETURN_TYPE (existing) = TREE_TYPE (e_type);
          TREE_TYPE (existing) = change_return_type (TREE_TYPE (d_type), e_type);
        }

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c7a0066a11ac01467ad123d14264652750fd01c9..3362a6f8f9ca81c0f1d263b0c1bf7bfab28e9229 100644 (file)
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27537,6 +27537,10 @@ tree
 template_for_substitution (tree decl)
 {
   tree tmpl = DECL_TI_TEMPLATE (decl);
+  if (VAR_P (decl))
+    if (tree partial = most_specialized_partial_spec (decl, tf_none))
+      if (partial != error_mark_node)
+       tmpl = TI_TEMPLATE (partial);
 
   /* Set TMPL to the template whose DECL_TEMPLATE_RESULT is the pattern
      for the instantiation.  This is not always the most general

diff --git a/gcc/testsuite/g++.dg/modules/auto-7.h b/gcc/testsuite/g++.dg/modules/auto-7.h
new file mode 100644 (file)
index 0000000..324b60c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/auto-7.h
@@ -0,0 +1,12 @@
+// PR c++/120644
+
+enum class E { E0, E1 };
+
+template <typename T>
+constexpr auto fmt_kind = E::E0;
+
+template <typename T>
+class opt{};
+
+template <typename T>
+constexpr auto fmt_kind<opt<T>> = E::E1;

diff --git a/gcc/testsuite/g++.dg/modules/auto-7_a.H b/gcc/testsuite/g++.dg/modules/auto-7_a.H
new file mode 100644 (file)
index 0000000..40cb0f8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/auto-7_a.H
@@ -0,0 +1,5 @@
+// PR c++/120644
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+
+#include "auto-7.h"

diff --git a/gcc/testsuite/g++.dg/modules/auto-7_b.C b/gcc/testsuite/g++.dg/modules/auto-7_b.C
new file mode 100644 (file)
index 0000000..c6ad37f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/auto-7_b.C
@@ -0,0 +1,5 @@
+// PR c++/120644
+// { dg-additional-options "-fmodules -fno-module-lazy" }
+
+#include "auto-7.h"
+import "auto-7_a.H";