[PATCH] D52919: Emit diagnostic note when calling an invalid function declaration.

[James Y Knight via Phabricator via cfe-commits]

jyknight created this revision.
jyknight added a reviewer: rsmith.

The comment said it was intentionally not emitting any diagnostic
because the declaration itself was already diagnosed. However,
everywhere else that wants to not emit a diagnostic without an extra
note emits note_invalid_subexpr_in_const_expr instead, which gets
suppressed later.

This was the only place which did not emit a diagnostic note.


https://reviews.llvm.org/D52919

Files:
  clang/lib/AST/ExprConstant.cpp
  clang/test/SemaCXX/enable_if.cpp


Index: clang/test/SemaCXX/enable_if.cpp
===================================================================
--- clang/test/SemaCXX/enable_if.cpp
+++ clang/test/SemaCXX/enable_if.cpp
@@ -414,7 +414,8 @@
 
 template <int N> constexpr int callTemplated() { return templated<N>(); }
 
-constexpr int B = callTemplated<0>(); // expected-error{{initialized by a constant expression}} expected-error at -2{{no matching function for call to 'templated'}} expected-note{{in instantiation of function template}} expected-note at -9{{candidate disabled}}
+constexpr int B = 10 + // the carat for the error should be pointing to the problematic call (on the next line), not here.
+    callTemplated<0>(); // expected-error{{initialized by a constant expression}} expected-error at -3{{no matching function for call to 'templated'}} expected-note{{in instantiation of function template}} expected-note at -10{{candidate disabled}}
 static_assert(callTemplated<1>() == 1, "");
 }
 
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -4330,10 +4330,13 @@
       Declaration->isConstexpr())
     return false;
 
-  // Bail out with no diagnostic if the function declaration itself is invalid.
-  // We will have produced a relevant diagnostic while parsing it.
-  if (Declaration->isInvalidDecl())
+  // Bail out if the function declaration itself is invalid.  We will
+  // have produced a relevant diagnostic while parsing it, so just
+  // note the problematic sub-expression.
+  if (Declaration->isInvalidDecl()) {
+    Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
     return false;
+  }
 
   // Can we evaluate this function call?
   if (Definition && Definition->isConstexpr() &&


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