Refactor cast<>'s in if conditionals, which can only assert on failure.

Summary:
This patch refactors several instances of cast<> used in if
conditionals.  Since cast<> asserts on failure, the else branch can
never be taken.

In some cases, the fix is to replace cast<> with dyn_cast<>.  While
others required the removal of the conditional and some minor
refactoring.

A discussion can be seen here: http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20190318/265044.html

Differential Revision: https://reviews.llvm.org/D59529

llvm-svn: 356441

1 files changed, 25 insertions, 28 deletions

diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index cff5ac66ca6..9158e902c9a 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -8460,44 +8460,41 @@ Error ASTImporter::ImportDefinition_New(Decl *From) {
   if (!To)
     return llvm::make_error<ImportError>();
 
-  if (auto *FromDC = cast<DeclContext>(From)) {
-    ASTNodeImporter Importer(*this);
+  auto *FromDC = cast<DeclContext>(From);
+  ASTNodeImporter Importer(*this);
 
-    if (auto *ToRecord = dyn_cast<RecordDecl>(To)) {
-      if (!ToRecord->getDefinition()) {
-        return Importer.ImportDefinition(
-            cast<RecordDecl>(FromDC), ToRecord,
-            ASTNodeImporter::IDK_Everything);
-      }
+  if (auto *ToRecord = dyn_cast<RecordDecl>(To)) {
+    if (!ToRecord->getDefinition()) {
+      return Importer.ImportDefinition(
+          cast<RecordDecl>(FromDC), ToRecord,
+          ASTNodeImporter::IDK_Everything);
     }
+  }
 
-    if (auto *ToEnum = dyn_cast<EnumDecl>(To)) {
-      if (!ToEnum->getDefinition()) {
-        return Importer.ImportDefinition(
-            cast<EnumDecl>(FromDC), ToEnum, ASTNodeImporter::IDK_Everything);
-      }
+  if (auto *ToEnum = dyn_cast<EnumDecl>(To)) {
+    if (!ToEnum->getDefinition()) {
+      return Importer.ImportDefinition(
+          cast<EnumDecl>(FromDC), ToEnum, ASTNodeImporter::IDK_Everything);
     }
+  }
 
-    if (auto *ToIFace = dyn_cast<ObjCInterfaceDecl>(To)) {
-      if (!ToIFace->getDefinition()) {
-        return Importer.ImportDefinition(
-            cast<ObjCInterfaceDecl>(FromDC), ToIFace,
-            ASTNodeImporter::IDK_Everything);
-      }
+  if (auto *ToIFace = dyn_cast<ObjCInterfaceDecl>(To)) {
+    if (!ToIFace->getDefinition()) {
+      return Importer.ImportDefinition(
+          cast<ObjCInterfaceDecl>(FromDC), ToIFace,
+          ASTNodeImporter::IDK_Everything);
     }
+  }
 
-    if (auto *ToProto = dyn_cast<ObjCProtocolDecl>(To)) {
-      if (!ToProto->getDefinition()) {
-        return Importer.ImportDefinition(
-            cast<ObjCProtocolDecl>(FromDC), ToProto,
-            ASTNodeImporter::IDK_Everything);
-      }
+  if (auto *ToProto = dyn_cast<ObjCProtocolDecl>(To)) {
+    if (!ToProto->getDefinition()) {
+      return Importer.ImportDefinition(
+          cast<ObjCProtocolDecl>(FromDC), ToProto,
+          ASTNodeImporter::IDK_Everything);
     }
-
-    return Importer.ImportDeclContext(FromDC, true);
   }
 
-  return Error::success();
+  return Importer.ImportDeclContext(FromDC, true);
 }
 
 void ASTImporter::ImportDefinition(Decl *From) {