c++: replace in_template_function

All uses of in_template_function except for the one in cp_make_fname_decl
seem like they could be generalized to consider any template context.
To that end this patch replaces the predicate with a generalized
in_template_context predicate that returns true if we're inside any
template context.  If we legitimately need to consider only function
contexts, as in cp_make_fname_decl, we can just additionally check e.g.
current_function_decl.

One concrete benefit of this, which the adjusted testcase below
demonstrates, is that we no longer instantiate/odr-use entities based on
uses within a non-function template.

gcc/cp/ChangeLog:

	* class.cc (build_base_path): Check in_template_context instead
	of in_template_function.
	(resolves_to_fixed_type_p): Likewise.
	* cp-tree.h (in_template_context): Define.
	(in_template_function): Remove.
	* decl.cc (cp_make_fname_decl): Check current_function_decl
	and in_template_context instead of in_template_function.
	* decl2.cc (mark_used): Check in_template_context instead of
	in_template_function.
	* pt.cc (in_template_function): Remove.
	* semantics.cc (enforce_access): Check in_template_context
	instead of current_template_parms directly.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Waddress-of-packed-member2.C: No longer expect a()
	to be marked as odr-used.

7 files changed, 7 insertions, 26 deletions

diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc
index bc84f4f..7787592 100644
--- a/gcc/cp/class.cc
+++ b/gcc/cp/class.cc
@@ -344,7 +344,7 @@ build_base_path (enum tree_code code,
 
   bool uneval = (cp_unevaluated_operand != 0
 		 || processing_template_decl
-		 || in_template_function ());
+		 || in_template_context);
 
   /* For a non-pointer simple base reference, express it as a COMPONENT_REF
      without taking its address (and so causing lambda capture, 91933).  */
@@ -8055,7 +8055,7 @@ resolves_to_fixed_type_p (tree instance, int* nonnull)
   /* processing_template_decl can be false in a template if we're in
      instantiate_non_dependent_expr, but we still want to suppress
      this check.  */
-  if (in_template_function ())
+  if (in_template_context)
     {
       /* In a template we only care about the type of the result.  */
       if (nonnull)
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index a1b882f..ce2095c 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1924,6 +1924,7 @@ extern GTY(()) struct saved_scope *scope_chain;
 #define current_template_parms scope_chain->template_parms
 #define current_template_depth \
   (current_template_parms ? TMPL_PARMS_DEPTH (current_template_parms) : 0)
+#define in_template_context (current_template_parms != NULL_TREE)
 
 #define processing_template_decl scope_chain->x_processing_template_decl
 #define processing_specialization scope_chain->x_processing_specialization
@@ -7353,7 +7354,6 @@ extern tree lookup_template_variable		(tree, tree);
 extern bool uses_template_parms			(tree);
 extern bool uses_template_parms_level		(tree, int);
 extern bool uses_outer_template_parms_in_constraints (tree);
-extern bool in_template_function		(void);
 extern bool need_generic_capture		(void);
 extern tree instantiate_class_template		(tree);
 extern tree instantiate_template		(tree, tree, tsubst_flags_t);
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index a672e48..3985c6d 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -5021,7 +5021,7 @@ cp_make_fname_decl (location_t loc, tree id, int type_dep)
   tree domain = NULL_TREE;
   tree init = NULL_TREE;
 
-  if (!(type_dep && in_template_function ()))
+  if (!(type_dep && current_function_decl && in_template_context))
     {
       const char *name = NULL;
       bool release_name = false;
diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index b510cda..b402bef 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -5782,7 +5782,7 @@ mark_used (tree decl, tsubst_flags_t complain /* = tf_warning_or_error */)
 	  && DECL_OMP_DECLARE_REDUCTION_P (decl)))
     maybe_instantiate_decl (decl);
 
-  if (processing_template_decl || in_template_function ())
+  if (processing_template_decl || in_template_context)
     return true;
 
   /* Check this too in case we're within instantiate_non_dependent_expr.  */
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 7fb3e75..244b0b0 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -10951,25 +10951,6 @@ uses_template_parms (tree t)
     return instantiation_dependent_expression_p (t);
 }
 
-/* Returns true iff we're processing an incompletely instantiated function
-   template.  Useful instead of processing_template_decl because the latter
-   is set to 0 during instantiate_non_dependent_expr.  */
-
-bool
-in_template_function (void)
-{
-  /* Inspect the less volatile cfun->decl instead of current_function_decl;
-     the latter might get set for e.g. access checking during satisfaction.  */
-  tree fn = cfun ? cfun->decl : NULL_TREE;
-  bool ret;
-  ++processing_template_decl;
-  ret = (fn && DECL_LANG_SPECIFIC (fn)
-	 && DECL_TEMPLATE_INFO (fn)
-	 && any_dependent_template_arguments_p (DECL_TI_ARGS (fn)));
-  --processing_template_decl;
-  return ret;
-}
-
 /* Returns true if T depends on any template parameter with level LEVEL.  */
 
 bool
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 05df628..0843b5e 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -346,7 +346,7 @@ enforce_access (tree basetype_path, tree decl, tree diag_decl,
     }
 
   tree cs = current_scope ();
-  if (current_template_parms
+  if (in_template_context
       && (CLASS_TYPE_P (cs) || TREE_CODE (cs) == FUNCTION_DECL))
     if (tree template_info = get_template_info (cs))
       {
diff --git a/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member2.C b/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member2.C
index e9bf7ca..d619b28 100644
--- a/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member2.C
+++ b/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member2.C
@@ -1,7 +1,7 @@
 // PR c++/89973
 // { dg-do compile { target c++14 } }
 
-constexpr int a(); // { dg-warning "used but never defined" }
+constexpr int a();
 
 template <typename>
 constexpr void *b = a(); // { dg-error "invalid conversion" }