Re: [PATCH 2/2] c++: Respect current_constraint_diagnosis_depth in diagnose_compound_requirement

[Jason Merrill via Gcc-patches]

On 3/27/20 12:20 AM, Patrick Palka wrote:

On Mon, 9 Mar 2020, Patrick Palka wrote:

The first patch tries to avoid changing our current default diagnostics.  But
for the sake of consistency we arguably should also respect
current_constraint_diagnosis_depth in diagnose_compound_requirement() like we do
in the other error-replaying diagnostic routine.  But doing so would be a change
to our default diagnostics behavior, so the change has been split out into this
separate patch for separate consideration.

Ping.  Here's a rebased version of this patch.

OK.

-- >8 --

gcc/cp/ChangeLog:

        * constraint.cc (diagnose_compound_requirement): When diagnosing a
        compound requirement, maybe replay the satisfaction failure, subject to
        the current diagnosis depth.

gcc/testsuite/ChangeLog:

        * g++.dg/concepts/diagnostic1.C: Pass -fconcepts-diagnostics-depth=2.
        * g++.dg/concepts/diagnostic5.C: Adjust expected diagnostics.
        * g++.dg/cpp2a/concepts-requires5.C: Pass
        -fconcepts-diagnostics-depth=2.
---
  gcc/cp/constraint.cc                          | 28 +++++++++++++------
  gcc/testsuite/g++.dg/concepts/diagnostic1.C   |  1 +
  gcc/testsuite/g++.dg/concepts/diagnostic5.C   |  5 +---
  gcc/testsuite/g++.dg/cpp2a/concepts-iconv1.C  |  1 +
  .../g++.dg/cpp2a/concepts-requires5.C         |  2 +-
  5 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 76c520318c3..571c7cbdd38 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3308,20 +3308,30 @@ diagnose_compound_requirement (tree req, tree args, 
tree in_decl)
          if (!type_deducible_p (expr, type, placeholder, args, quiet))
            {
              tree orig_expr = TREE_OPERAND (req, 0);
-             inform (loc, "%qE does not satisfy return-type-requirement",
-                     orig_expr);
-
-             /* Further explain the reason for the error.  */
-             type_deducible_p (expr, type, placeholder, args, noisy);
+             if (diagnosing_failed_constraint::replay_errors_p ())
+               {
+                 inform (loc,
+                         "%qE does not satisfy return-type-requirement, "
+                         "because", orig_expr);
+                 /* Further explain the reason for the error.  */
+                 type_deducible_p (expr, type, placeholder, args, noisy);
+               }
+             else
+               inform (loc, "%qE does not satisfy return-type-requirement",
+                       orig_expr);
            }
        }
        else if (!expression_convertible_p (expr, type, quiet))
        {
          tree orig_expr = TREE_OPERAND (req, 0);
-         inform (loc, "cannot convert %qE to %qT", orig_expr, type);
-
-         /* Further explain the reason for the error.  */
-         expression_convertible_p (expr, type, noisy);
+         if (diagnosing_failed_constraint::replay_errors_p ())
+           {
+             inform (loc, "cannot convert %qE to %qT because", orig_expr, 
type);
+             /* Further explain the reason for the error.  */
+             expression_convertible_p (expr, type, noisy);
+           }
+         else
+           inform (loc, "cannot convert %qE to %qT", orig_expr, type);
        }
      }
  }
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic1.C 
b/gcc/testsuite/g++.dg/concepts/diagnostic1.C
index 7da08db2792..c6589e2e671 100644
--- a/gcc/testsuite/g++.dg/concepts/diagnostic1.C
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic1.C
@@ -1,6 +1,7 @@
  // PR c++/67159
  // { dg-do compile { target c++17_only } }
  // { dg-options "-fconcepts" }
+// { dg-additional-options "-fconcepts-diagnostics-depth=2" }

template <class T, class U>

  concept bool SameAs = __is_same_as(T, U);
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic5.C 
b/gcc/testsuite/g++.dg/concepts/diagnostic5.C
index 2641dc18423..0d890d6f548 100644
--- a/gcc/testsuite/g++.dg/concepts/diagnostic5.C
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic5.C
@@ -4,8 +4,7 @@
  template<typename T>
    concept c1 = requires { typename T::blah; };
  // { dg-message "satisfaction of .c1<T>. .with T = char." "" { target *-*-* } 
.-1 }
-// { dg-message "satisfaction of .c1<char\\*>." "" { target *-*-* } .-2 }
-// { dg-message ".typename T::blah. is invalid" "" { target *-*-* } .-3 }
+// { dg-message ".typename T::blah. is invalid" "" { target *-*-* } .-2 }

template<typename T>

    concept c2 = requires (T x) { *x; };
@@ -27,8 +26,6 @@ template<typename T>
    concept c5 = requires (T x) { { &x } -> c1; };
  // { dg-message "satisfaction of .c5<T>. .with T = char." "" { target *-*-* } 
.-1 }
  // { dg-message "in requirements with .char x." "" { target *-*-* } .-2 }
-// { dg-message "does not satisfy return-type-requirement" "" { target *-*-* } 
.-3 }
-// { dg-error "deduced expression type does not satisfy" "" { target *-*-* } 
.-4 }

template<typename T>

    requires (c1<T> || c2<T>) || (c3<T> || c4<T>) || c5<T> // { dg-message "49: no 
operand" }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-iconv1.C 
b/gcc/testsuite/g++.dg/cpp2a/concepts-iconv1.C
index 4d521c30748..4e2d13f8eb3 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-iconv1.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-iconv1.C
@@ -1,5 +1,6 @@
  // PR c++/67240
  // { dg-do compile { target c++2a } }
+// { dg-additional-options "-fconcepts-diagnostics-depth=2" }

template <class T, class U> concept Same = __is_same_as(T,U); diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires5.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires5.C

index 133d29e45a4..2f912b13d6a 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-requires5.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires5.C
@@ -1,5 +1,5 @@
  // { dg-do compile { target c++2a } }
-// { dg-additional-options -fconcepts-ts }
+// { dg-additional-options "-fconcepts-ts -fconcepts-diagnostics-depth=2" }

// Test conversion requirements (not in C++20)