[PATCH] c++: Output less irrelevant info for function template decl [PR100716]

[Matthias Kretz <m.kretz@gsi.de>]

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From: Matthias Kretz <kretz@kde.org>

Ensure dump_template_decl for function templates never prints template 
parameters after the function name (it did with -fno-pretty-templates) and 
skip output of irrelevant & confusing "[with T = T]" in dump_substitution.

gcc/cp/ChangeLog:

	PR c++/100716
	* error.c (dump_template_bindings): Include code to print
	"[with" and ']', conditional on whether anything is printed at
	all. This is tied to whether a semicolon is needed to separate
	multiple template parameters. If the template argument repeats
	the template parameter (T = T), then skip the parameter.
	(dump_substitution): Moved code to print "[with" and ']' to
	dump_template_bindings.
	(dump_function_decl): Partial revert of PR50828, which masked
	TFF_TEMPLATE_NAME for all of dump_function_decl. Now
	TFF_TEMPLATE_NAME is masked for the scope of the function and
	only carries through to dump_function_name.
	(dump_function_name): Avoid calling dump_template_parms if
	TFF_TEMPLATE_NAME is set.

gcc/testsuite/ChangeLog:

	PR c++/100716
	* g++.dg/diagnostic/pr100716.C: New test.
	* g++.dg/diagnostic/pr100716-1.C: Same test with
	-fno-pretty-templates.
---
 gcc/cp/error.c                               | 59 +++++++++++++++-----
 gcc/testsuite/g++.dg/diagnostic/pr100716-1.C | 54 ++++++++++++++++++
 gcc/testsuite/g++.dg/diagnostic/pr100716.C   | 54 ++++++++++++++++++
 3 files changed, 152 insertions(+), 15 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/diagnostic/pr100716-1.C
 create mode 100644 gcc/testsuite/g++.dg/diagnostic/pr100716.C


--
──────────────────────────────────────────────────────────────────────────
 Dr. Matthias Kretz                           https://mattkretz.github.io
 GSI Helmholtz Centre for Heavy Ion Research               https://gsi.de
 std::experimental::simd              https://github.com/VcDevel/std-simd
──────────────────────────────────────────────────────────────────────────

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diff --git a/gcc/cp/error.c b/gcc/cp/error.c
index 010fbce41a7..bc0b68f07e0 100644
--- a/gcc/cp/error.c
+++ b/gcc/cp/error.c
@@ -381,7 +381,32 @@ static void
 dump_template_bindings (cxx_pretty_printer *pp, tree parms, tree args,
                         vec<tree, va_gc> *typenames)
 {
-  bool need_semicolon = false;
+  struct prepost_semicolon
+  {
+    cxx_pretty_printer *pp;
+    bool need_semicolon = false;
+
+    void operator()()
+    {
+      if (need_semicolon)
+	pp_separate_with_semicolon (pp);
+      else
+	{
+	  pp_cxx_whitespace (pp);
+	  pp_cxx_left_bracket (pp);
+	  pp->translate_string ("with");
+	  pp_cxx_whitespace (pp);
+	  need_semicolon = true;
+	}
+    }
+
+    ~prepost_semicolon()
+    {
+      if (need_semicolon)
+	pp_cxx_right_bracket (pp);
+    }
+  } semicolon_or_introducer = {pp};
+
   int i;
   tree t;
 
@@ -405,10 +430,19 @@ dump_template_bindings (cxx_pretty_printer *pp, tree parms, tree args,
 	  if (lvl_args && NUM_TMPL_ARGS (lvl_args) > arg_idx)
 	    arg = TREE_VEC_ELT (lvl_args, arg_idx);
 
-	  if (need_semicolon)
-	    pp_separate_with_semicolon (pp);
-	  dump_template_parameter (pp, TREE_VEC_ELT (p, i),
-                                   TFF_PLAIN_IDENTIFIER);
+	  tree parm_i = TREE_VEC_ELT (p, i);
+	  /* Skip this parameter if it just noise such as "T = T".  */
+	  if (arg && TREE_CODE (arg) == TEMPLATE_TYPE_PARM
+		&& TREE_CODE (parm_i) == TREE_LIST
+		&& TREE_CODE (TREE_VALUE (parm_i)) == TYPE_DECL
+		&& TREE_CODE (TREE_TYPE (TREE_VALUE (parm_i)))
+		     == TEMPLATE_TYPE_PARM
+		&& DECL_NAME (TREE_VALUE (parm_i))
+		     == DECL_NAME (TREE_CHAIN (arg)))
+	    continue;
+
+	  semicolon_or_introducer();
+	  dump_template_parameter (pp, parm_i, TFF_PLAIN_IDENTIFIER);
 	  pp_cxx_whitespace (pp);
 	  pp_equal (pp);
 	  pp_cxx_whitespace (pp);
@@ -424,7 +458,6 @@ dump_template_bindings (cxx_pretty_printer *pp, tree parms, tree args,
 	    pp_string (pp, M_("<missing>"));
 
 	  ++arg_idx;
-	  need_semicolon = true;
 	}
 
       parms = TREE_CHAIN (parms);
@@ -446,8 +479,7 @@ dump_template_bindings (cxx_pretty_printer *pp, tree parms, tree args,
 
   FOR_EACH_VEC_SAFE_ELT (typenames, i, t)
     {
-      if (need_semicolon)
-	pp_separate_with_semicolon (pp);
+      semicolon_or_introducer();
       dump_type (pp, t, TFF_PLAIN_IDENTIFIER);
       pp_cxx_whitespace (pp);
       pp_equal (pp);
@@ -1652,12 +1684,7 @@ dump_substitution (cxx_pretty_printer *pp,
       && !(flags & TFF_NO_TEMPLATE_BINDINGS))
     {
       vec<tree, va_gc> *typenames = t ? find_typenames (t) : NULL;
-      pp_cxx_whitespace (pp);
-      pp_cxx_left_bracket (pp);
-      pp->translate_string ("with");
-      pp_cxx_whitespace (pp);
       dump_template_bindings (pp, template_parms, template_args, typenames);
-      pp_cxx_right_bracket (pp);
     }
 }
 
@@ -1698,7 +1725,8 @@ dump_function_decl (cxx_pretty_printer *pp, tree t, int flags)
   bool constexpr_p;
   tree ret = NULL_TREE;
 
-  flags &= ~(TFF_UNQUALIFIED_NAME | TFF_TEMPLATE_NAME);
+  int dump_function_name_flags = flags & ~TFF_UNQUALIFIED_NAME;
+  flags = dump_function_name_flags & ~TFF_TEMPLATE_NAME;
   if (TREE_CODE (t) == TEMPLATE_DECL)
     t = DECL_TEMPLATE_RESULT (t);
 
@@ -1782,7 +1810,7 @@ dump_function_decl (cxx_pretty_printer *pp, tree t, int flags)
   else
     dump_scope (pp, CP_DECL_CONTEXT (t), flags);
 
-  dump_function_name (pp, t, flags);
+  dump_function_name (pp, t, dump_function_name_flags);
 
   if (!(flags & TFF_NO_FUNCTION_ARGUMENTS))
     {
@@ -2006,6 +2034,7 @@ dump_function_name (cxx_pretty_printer *pp, tree t, int flags)
   dump_module_suffix (pp, t);
 
   if (DECL_TEMPLATE_INFO (t)
+      && !(flags & TFF_TEMPLATE_NAME)
       && !DECL_FRIEND_PSEUDO_TEMPLATE_INSTANTIATION (t)
       && (TREE_CODE (DECL_TI_TEMPLATE (t)) != TEMPLATE_DECL
 	  || PRIMARY_TEMPLATE_P (DECL_TI_TEMPLATE (t))))
diff --git a/gcc/testsuite/g++.dg/diagnostic/pr100716-1.C b/gcc/testsuite/g++.dg/diagnostic/pr100716-1.C
new file mode 100644
index 00000000000..93490da6a83
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/pr100716-1.C
@@ -0,0 +1,54 @@
+// { dg-options "-fno-pretty-templates" }
+
+template<typename T>
+  struct A
+  {
+    template<typename U>
+      void f() {} // { dg-line Af }
+
+    template<typename U>
+      void g(U) {} // { dg-line Ag }
+  };
+
+template<typename T>
+  struct B
+  {
+    template<typename U>
+      void f(U) {} // { dg-line Bf }
+
+    template<typename U>
+      void g(U, T) {} // { dg-line Bg }
+  };
+
+struct C
+{
+  template<typename U>
+    void f(U) {} // { dg-line Cf }
+
+  template<typename U>
+    void g() {} // { dg-line Cg }
+};
+
+int main()
+{
+  A<int>().f(0); // { dg-error "no matching function for call to 'A<int>::f\\(int\\)'" }
+  // { dg-message "candidate: 'template<class U> void A<int>::f\\(\\)'" "" { target *-*-* } Af }
+
+  A<int>().g(); // { dg-error "no matching function for call to 'A<int>::g\\(\\)'" }
+  // { dg-message "candidate: 'template<class U> void A<int>::g\\(U\\)'" "" { target *-*-* } Ag }
+
+  B<int>().f(); // { dg-error "no matching function for call to 'B<int>::f\\(\\)'" }
+  // { dg-message "candidate: 'template<class U> void B<int>::f\\(U\\)'" "" { target *-*-* } Bf }
+
+  B<int>().g(); // { dg-error "no matching function for call to 'B<int>::g\\(\\)'" }
+  // { dg-message "candidate: 'template<class U> void B<int>::g\\(U, int\\)'" "" { target *-*-* } Bg }
+
+  B<float>().g(0); // { dg-error "no matching function for call to 'B<float>::g\\(int\\)'" }
+  // { dg-message "candidate: 'template<class U> void B<float>::g\\(U, float\\)'" "" { target *-*-* } Bg }
+
+  C().f(); // { dg-error "no matching function for call to 'C::f\\(\\)'" }
+  // { dg-message "candidate: 'template<class U> void C::f\\(U\\)'" "" { target *-*-* } Cf }
+
+  C().g(0); // { dg-error "no matching function for call to 'C::g\\(int\\)'" }
+  // { dg-message "candidate: 'template<class U> void C::g\\(\\)'" "" { target *-*-* } Cg }
+}
diff --git a/gcc/testsuite/g++.dg/diagnostic/pr100716.C b/gcc/testsuite/g++.dg/diagnostic/pr100716.C
new file mode 100644
index 00000000000..4a1f0a4e10a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/pr100716.C
@@ -0,0 +1,54 @@
+// { dg-options "-fpretty-templates" }
+
+template<typename T>
+  struct A
+  {
+    template<typename U>
+      void f() {} // { dg-line Af }
+
+    template<typename U>
+      void g(U) {} // { dg-line Ag }
+  };
+
+template<typename T>
+  struct B
+  {
+    template<typename U>
+      void f(U) {} // { dg-line Bf }
+
+    template<typename U>
+      void g(U, T) {} // { dg-line Bg }
+  };
+
+struct C
+{
+  template<typename U>
+    void f(U) {} // { dg-line Cf }
+
+  template<typename U>
+    void g() {} // { dg-line Cg }
+};
+
+int main()
+{
+  A<int>().f(0); // { dg-error "no matching function for call to 'A<int>::f\\(int\\)'" }
+  // { dg-message "candidate: 'template<class U> void A<T>::f\\(\\) \\\[with T = int\\\]'" "" { target *-*-* } Af }
+
+  A<int>().g(); // { dg-error "no matching function for call to 'A<int>::g\\(\\)'" }
+  // { dg-message "candidate: 'template<class U> void A<T>::g\\(U\\) \\\[with T = int\\\]'" "" { target *-*-* } Ag }
+
+  B<int>().f(); // { dg-error "no matching function for call to 'B<int>::f\\(\\)'" }
+  // { dg-message "candidate: 'template<class U> void B<T>::f\\(U\\) \\\[with T = int\\\]'" "" { target *-*-* } Bf }
+
+  B<int>().g(); // { dg-error "no matching function for call to 'B<int>::g\\(\\)'" }
+  // { dg-message "candidate: 'template<class U> void B<T>::g\\(U, T\\) \\\[with T = int\\\]'" "" { target *-*-* } Bg }
+
+  B<float>().g(0); // { dg-error "no matching function for call to 'B<float>::g\\(int\\)'" }
+  // { dg-message "candidate: 'template<class U> void B<T>::g\\(U, T\\) \\\[with T = float\\\]'" "" { target *-*-* } Bg }
+
+  C().f(); // { dg-error "no matching function for call to 'C::f\\(\\)'" }
+  // { dg-message "candidate: 'template<class U> void C::f\\(U\\)'" "" { target *-*-* } Cf }
+
+  C().g(0); // { dg-error "no matching function for call to 'C::g\\(int\\)'" }
+  // { dg-message "candidate: 'template<class U> void C::g\\(\\)'" "" { target *-*-* } Cg }
+}