PR38627: Fix handling of exception specification adjustment for

destructors.

We previously tried to patch up the exception specification after
completing the class, which went wrong when the exception specification
was needed within the class body (in particular, by a friend
redeclaration of the destructor in a nested class). We now mark the
destructor as having a not-yet-computed exception specification
immediately after creating it.

This requires delaying various checks against the exception
specification (where we'd previously have just got the wrong exception
specification, and now find we have an exception specification that we
can't compute yet) when those checks fire while the class is being
defined.

This also exposed an issue that we were missing a CodeSynthesisContext
for computation of exception specifications (otherwise we'd fail to make
the module containing the definition of the class visible when computing
its members' exception specs). Adding that incidentally also gives us a
diagnostic quality improvement.

This has also exposed an pre-existing problem: making the exception
specification evaluation context a non-SFINAE context (as it should be)
results in a bootstrap failure; PR38850 filed for this.

llvm-svn: 341499

1 files changed, 30 insertions, 17 deletions

diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index ec9dab8f53a..f3e1563c3a8 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -230,6 +230,16 @@ Sema::UpdateExceptionSpec(FunctionDecl *FD,
     Context.adjustExceptionSpec(Redecl, ESI);
 }
 
+static bool exceptionSpecNotKnownYet(const FunctionDecl *FD) {
+  auto *MD = dyn_cast<CXXMethodDecl>(FD);
+  if (!MD)
+    return false;
+
+  auto EST = MD->getType()->castAs<FunctionProtoType>()->getExceptionSpecType();
+  return EST == EST_Unparsed ||
+         (EST == EST_Unevaluated && MD->getParent()->isBeingDefined());
+};
+
 static bool CheckEquivalentExceptionSpecImpl(
     Sema &S, const PartialDiagnostic &DiagID, const PartialDiagnostic &NoteID,
     const FunctionProtoType *Old, SourceLocation OldLoc,
@@ -278,6 +288,14 @@ bool Sema::CheckEquivalentExceptionSpec(FunctionDecl *Old, FunctionDecl *New) {
     ReturnValueOnError = false;
   }
 
+  // If we're befriending a member function of a class that's currently being
+  // defined, we might not be able to work out its exception specification yet.
+  // If not, defer the check until later.
+  if (exceptionSpecNotKnownYet(Old) || exceptionSpecNotKnownYet(New)) {
+    DelayedEquivalentExceptionSpecChecks.push_back({New, Old});
+    return false;
+  }
+
   // Check the types as written: they must match before any exception
   // specification adjustment is applied.
   if (!CheckEquivalentExceptionSpecImpl(
@@ -904,26 +922,21 @@ bool Sema::CheckOverridingFunctionExceptionSpec(const CXXMethodDecl *New,
   if (New->getType()->castAs<FunctionProtoType>()->getExceptionSpecType() ==
       EST_Unparsed)
     return false;
-  if (getLangOpts().CPlusPlus11 && isa<CXXDestructorDecl>(New)) {
-    // Don't check uninstantiated template destructors at all. We can only
-    // synthesize correct specs after the template is instantiated.
-    if (New->getParent()->isDependentType())
-      return false;
-    if (New->getParent()->isBeingDefined()) {
-      // The destructor might be updated once the definition is finished. So
-      // remember it and check later.
-      DelayedExceptionSpecChecks.push_back(std::make_pair(New, Old));
-      return false;
-    }
-  }
-  // If the old exception specification hasn't been parsed yet, remember that
-  // we need to perform this check when we get to the end of the outermost
+
+  // Don't check uninstantiated template destructors at all. We can only
+  // synthesize correct specs after the template is instantiated.
+  if (isa<CXXDestructorDecl>(New) && New->getParent()->isDependentType())
+    return false;
+
+  // If the old exception specification hasn't been parsed yet, or the new
+  // exception specification can't be computed yet, remember that we need to
+  // perform this check when we get to the end of the outermost
   // lexically-surrounding class.
-  if (Old->getType()->castAs<FunctionProtoType>()->getExceptionSpecType() ==
-      EST_Unparsed) {
-    DelayedExceptionSpecChecks.push_back(std::make_pair(New, Old));
+  if (exceptionSpecNotKnownYet(Old) || exceptionSpecNotKnownYet(New)) {
+    DelayedOverridingExceptionSpecChecks.push_back({New, Old});
     return false;
   }
+
   unsigned DiagID = diag::err_override_exception_spec;
   if (getLangOpts().MicrosoftExt)
     DiagID = diag::ext_override_exception_spec;