[CSDiagnostics] Move check inside getDeclContext()

(cherry picked from commit 2339b5f)

Author: theblixguy

lib/Sema/CSDiagnostics.cpp

@@ -2958,10 +2958,10 @@ bool MissingGenericArgumentsFailure::diagnoseForAnchor(
   if (!diagnosed)
     return false;
 
-  if (!hasDecl())
+  auto *DC = getDeclContext();
+  if (!DC)
     return true;
 
-  auto *DC = getDeclContext();
   if (auto *SD = dyn_cast<SubscriptDecl>(DC)) {
     emitDiagnostic(SD, diag::note_call_to_subscript, SD->getFullName());
     return true;
@@ -3011,15 +3011,14 @@ bool MissingGenericArgumentsFailure::diagnoseParameter(
     emitDiagnostic(loc, diag::unbound_generic_parameter, GP);
   }
 
-  if (!hasDecl())
+  Type baseTyForNote;
+  auto *DC = getDeclContext();
+  if (!DC)
     return true;
 
   if (!hasLoc(GP))
     return true;
 
-  Type baseTyForNote;
-  auto *DC = getDeclContext();
-
   if (auto *NTD =
           dyn_cast_or_null<NominalTypeDecl>(DC->getSelfNominalTypeDecl())) {
     baseTyForNote = NTD->getDeclaredType();
@@ -3040,6 +3039,9 @@ void MissingGenericArgumentsFailure::emitGenericSignatureNote(
   auto &TC = getTypeChecker();
   auto *paramDC = getDeclContext();
 
+  if (!paramDC)
+    return;
+
   auto *GTD = dyn_cast<GenericTypeDecl>(paramDC);
   if (!GTD || anchor.is<Expr *>())
     return;

lib/Sema/CSDiagnostics.h

@@ -1334,10 +1334,10 @@ class MissingGenericArgumentsFailure final : public FailureDiagnostic {
 
   DeclContext *getDeclContext() const {
     auto *GP = Parameters.front();
-    return GP->getDecl()->getDeclContext();
-  }
+    auto *decl = GP->getDecl();
 
-  bool hasDecl() const { return Parameters.front()->getDecl() != nullptr; }
+    return decl ? decl->getDeclContext() : nullptr;
+  }
 
   bool diagnoseAsError() override;
 

validation-test/compiler_crashers_2_fixed/sr11236.swift

@@ -10,4 +10,3 @@ public func myTri<T: Comparable, U: Comparable> (retval: UnsafeMutablePointer<U>
   retval.initialize(to: trichotomy(x: x, y: y))
 }
 
-print("Hello, World!")