1 files changed, 32 insertions, 21 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index a57ee7b0ff2..e1921f0ddf7 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -1827,6 +1827,25 @@ Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
       VK, FoundD, TemplateArgs, getNonOdrUseReasonInCurrentContext(D));
   MarkDeclRefReferenced(E);
 
+  // C++ [except.spec]p17:
+  //   An exception-specification is considered to be needed when:
+  //   - in an expression, the function is the unique lookup result or
+  //     the selected member of a set of overloaded functions.
+  //
+  // We delay doing this until after we've built the function reference and
+  // marked it as used so that:
+  //  a) if the function is defaulted, we get errors from defining it before /
+  //     instead of errors from computing its exception specification, and
+  //  b) if the function is a defaulted comparison, we can use the body we
+  //     build when defining it as input to the exception specification
+  //     computation rather than computing a new body.
+  if (auto *FPT = Ty->getAs<FunctionProtoType>()) {
+    if (isUnresolvedExceptionSpec(FPT->getExceptionSpecType())) {
+      if (auto *NewFPT = ResolveExceptionSpec(NameInfo.getLoc(), FPT))
+        E->setType(Context.getQualifiedType(NewFPT, Ty.getQualifiers()));
+    }
+  }
+
   if (getLangOpts().ObjCWeak && isa<VarDecl>(D) &&
       Ty.getObjCLifetime() == Qualifiers::OCL_Weak && !isUnevaluatedContext() &&
       !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, E->getBeginLoc()))
@@ -3009,14 +3028,6 @@ ExprResult Sema::BuildDeclarationNameExpr(
     QualType type = VD->getType();
     if (type.isNull())
       return ExprError();
-    if (auto *FPT = type->getAs<FunctionProtoType>()) {
-      // C++ [except.spec]p17:
-      //   An exception-specification is considered to be needed when:
-      //   - in an expression, the function is the unique lookup result or
-      //     the selected member of a set of overloaded functions.
-      ResolveExceptionSpec(Loc, FPT);
-      type = VD->getType();
-    }
     ExprValueKind valueKind = VK_RValue;
 
     switch (D->getKind()) {
@@ -15480,19 +15491,6 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
        Func->getMemberSpecializationInfo()))
     checkSpecializationVisibility(Loc, Func);
 
-  // C++14 [except.spec]p17:
-  //   An exception-specification is considered to be needed when:
-  //   - the function is odr-used or, if it appears in an unevaluated operand,
-  //     would be odr-used if the expression were potentially-evaluated;
-  //
-  // Note, we do this even if MightBeOdrUse is false. That indicates that the
-  // function is a pure virtual function we're calling, and in that case the
-  // function was selected by overload resolution and we need to resolve its
-  // exception specification for a different reason.
-  const FunctionProtoType *FPT = Func->getType()->getAs<FunctionProtoType>();
-  if (FPT && isUnresolvedExceptionSpec(FPT->getExceptionSpecType()))
-    ResolveExceptionSpec(Loc, FPT);
-
   if (getLangOpts().CUDA)
     CheckCUDACall(Loc, Func);
 
@@ -15601,6 +15599,19 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
     });
   }
 
+  // C++14 [except.spec]p17:
+  //   An exception-specification is considered to be needed when:
+  //   - the function is odr-used or, if it appears in an unevaluated operand,
+  //     would be odr-used if the expression were potentially-evaluated;
+  //
+  // Note, we do this even if MightBeOdrUse is false. That indicates that the
+  // function is a pure virtual function we're calling, and in that case the
+  // function was selected by overload resolution and we need to resolve its
+  // exception specification for a different reason.
+  const FunctionProtoType *FPT = Func->getType()->getAs<FunctionProtoType>();
+  if (FPT && isUnresolvedExceptionSpec(FPT->getExceptionSpecType()))
+    ResolveExceptionSpec(Loc, FPT);
+
   // If this is the first "real" use, act on that.
   if (OdrUse == OdrUseContext::Used && !Func->isUsed(/*CheckUsedAttr=*/false)) {
     // Keep track of used but undefined functions.