Revert "[clang][Interp] Fix CheckCallable for undefined-and-not-constexpr fns"

This reverts commit d00b355.

This breaks the ms-constexpr test:
https://lab.llvm.org/buildbot/#/builders/144/builds/2605

Author: tbaederr

clang/lib/AST/Interp/Interp.cpp

@@ -579,61 +579,57 @@ bool CheckCallable(InterpState &S, CodePtr OpPC, const Function *F) {
     return false;
   }
 
-  if (F->isConstexpr() && F->hasBody() && F->getDecl()->isConstexpr())
-    return true;
-
-  // Implicitly constexpr.
-  if (F->isLambdaStaticInvoker())
-    return true;
-
-  const SourceLocation &Loc = S.Current->getLocation(OpPC);
-  if (S.getLangOpts().CPlusPlus11) {
-    const FunctionDecl *DiagDecl = F->getDecl();
+  if (!F->isConstexpr() || !F->hasBody()) {
+    const SourceLocation &Loc = S.Current->getLocation(OpPC);
+    if (S.getLangOpts().CPlusPlus11) {
+      const FunctionDecl *DiagDecl = F->getDecl();
 
-    // Invalid decls have been diagnosed before.
-    if (DiagDecl->isInvalidDecl())
-      return false;
+      // Invalid decls have been diagnosed before.
+      if (DiagDecl->isInvalidDecl())
+        return false;
 
-    // If this function is not constexpr because it is an inherited
-    // non-constexpr constructor, diagnose that directly.
-    const auto *CD = dyn_cast<CXXConstructorDecl>(DiagDecl);
-    if (CD && CD->isInheritingConstructor()) {
-      const auto *Inherited = CD->getInheritedConstructor().getConstructor();
-      if (!Inherited->isConstexpr())
-        DiagDecl = CD = Inherited;
-    }
+      // If this function is not constexpr because it is an inherited
+      // non-constexpr constructor, diagnose that directly.
+      const auto *CD = dyn_cast<CXXConstructorDecl>(DiagDecl);
+      if (CD && CD->isInheritingConstructor()) {
+        const auto *Inherited = CD->getInheritedConstructor().getConstructor();
+        if (!Inherited->isConstexpr())
+          DiagDecl = CD = Inherited;
+      }
 
-    // FIXME: If DiagDecl is an implicitly-declared special member function
-    // or an inheriting constructor, we should be much more explicit about why
-    // it's not constexpr.
-    if (CD && CD->isInheritingConstructor()) {
-      S.FFDiag(Loc, diag::note_constexpr_invalid_inhctor, 1)
+      // FIXME: If DiagDecl is an implicitly-declared special member function
+      // or an inheriting constructor, we should be much more explicit about why
+      // it's not constexpr.
+      if (CD && CD->isInheritingConstructor()) {
+        S.FFDiag(Loc, diag::note_constexpr_invalid_inhctor, 1)
           << CD->getInheritedConstructor().getConstructor()->getParent();
-      S.Note(DiagDecl->getLocation(), diag::note_declared_at);
-    } else {
-      // Don't emit anything if the function isn't defined and we're checking
-      // for a constant expression. It might be defined at the point we're
-      // actually calling it.
-      bool IsExtern = DiagDecl->getStorageClass() == SC_Extern;
-      if (!DiagDecl->isDefined() && !IsExtern && DiagDecl->isConstexpr() &&
-          S.checkingPotentialConstantExpression())
-        return false;
+        S.Note(DiagDecl->getLocation(), diag::note_declared_at);
+      } else {
+        // Don't emit anything if the function isn't defined and we're checking
+        // for a constant expression. It might be defined at the point we're
+        // actually calling it.
+        bool IsExtern = DiagDecl->getStorageClass() == SC_Extern;
+        if (!DiagDecl->isDefined() && !IsExtern &&
+            S.checkingPotentialConstantExpression())
+          return false;
 
-      // If the declaration is defined, declared 'constexpr' _and_ has a body,
-      // the below diagnostic doesn't add anything useful.
-      if (DiagDecl->isDefined() && DiagDecl->isConstexpr() &&
-          DiagDecl->hasBody())
-        return false;
+        // If the declaration is defined, declared 'constexpr' _and_ has a body,
+        // the below diagnostic doesn't add anything useful.
+        if (DiagDecl->isDefined() && DiagDecl->isConstexpr() &&
+            DiagDecl->hasBody())
+          return false;
 
-      S.FFDiag(Loc, diag::note_constexpr_invalid_function, 1)
+        S.FFDiag(Loc, diag::note_constexpr_invalid_function, 1)
           << DiagDecl->isConstexpr() << (bool)CD << DiagDecl;
-      S.Note(DiagDecl->getLocation(), diag::note_declared_at);
+        S.Note(DiagDecl->getLocation(), diag::note_declared_at);
+      }
+    } else {
+      S.FFDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
     }
-  } else {
-    S.FFDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
+    return false;
   }
 
-  return false;
+  return true;
 }
 
 bool CheckCallDepth(InterpState &S, CodePtr OpPC) {

clang/lib/AST/Interp/Interp.h

@@ -2531,14 +2531,14 @@ inline bool Call(InterpState &S, CodePtr OpPC, const Function *Func,
       if (!CheckInvoke(S, OpPC, ThisPtr))
         return false;
     }
+
+    if (S.checkingPotentialConstantExpression())
+      return false;
   }
 
   if (!CheckCallable(S, OpPC, Func))
     return false;
 
-  if (Func->hasThisPointer() && S.checkingPotentialConstantExpression())
-    return false;
-
   if (!CheckCallDepth(S, OpPC))
     return false;