AST: Small cleanup for ASTContext::getOverrideGenericSignature()

Author: slavapestov

lib/AST/ASTContext.cpp

@@ -4354,42 +4354,28 @@ ASTContext::getOverrideGenericSignature(const ValueDecl *base,
   auto derivedGenericCtx = derived->getAsGenericContext();
   auto &ctx = base->getASTContext();
 
-  if (!baseGenericCtx) {
+  if (!baseGenericCtx || !derivedGenericCtx)
     return nullptr;
-  }
 
   auto baseClass = base->getDeclContext()->getSelfClassDecl();
-
-  if (!baseClass) {
+  if (!baseClass)
     return nullptr;
-  }
 
   auto derivedClass = derived->getDeclContext()->getSelfClassDecl();
-  auto baseClassSig = baseClass->getGenericSignature();
-
-  if (!derivedClass) {
+  if (!derivedClass)
     return nullptr;
-  }
 
-  if (derivedClass->getSuperclass().isNull()) {
+  if (derivedClass->getSuperclass().isNull())
     return nullptr;
-  }
 
-  if (!derivedGenericCtx || !derivedGenericCtx->isGeneric()) {
+  if (baseGenericCtx->getGenericSignature().isNull() ||
+      derivedGenericCtx->getGenericSignature().isNull())
     return nullptr;
-  }
-
-  if (derivedClass->getGenericSignature().isNull() &&
-      !baseGenericCtx->isGeneric()) {
-    return nullptr;
-  }
 
+  auto baseClassSig = baseClass->getGenericSignature();
   auto subMap = derivedClass->getSuperclass()->getContextSubstitutionMap(
       derivedClass->getModuleContext(), baseClass);
 
-  if (baseGenericCtx->getGenericSignature().isNull()) {
-    return nullptr;
-  }
   unsigned derivedDepth = 0;
 
   auto key = OverrideSignatureKey(baseGenericCtx->getGenericSignature(),
@@ -4405,9 +4391,11 @@ ASTContext::getOverrideGenericSignature(const ValueDecl *base,
     derivedDepth = derivedSig->getGenericParams().back()->getDepth() + 1;
 
   SmallVector<GenericTypeParamType *, 2> addedGenericParams;
-  for (auto gp : *derivedGenericCtx->getGenericParams()) {
-    addedGenericParams.push_back(
-        gp->getDeclaredInterfaceType()->castTo<GenericTypeParamType>());
+  if (auto *gpList = derivedGenericCtx->getGenericParams()) {
+    for (auto gp : *gpList) {
+      addedGenericParams.push_back(
+          gp->getDeclaredInterfaceType()->castTo<GenericTypeParamType>());
+    }
   }
 
   unsigned baseDepth = 0;