[unittests] Add a fixture for Sema unit tests

unittests/Sema/SemaFixture.cpp

@@ -0,0 +1,36 @@
+//===--- SemaFixture.cpp - Helper for setting up Sema context --------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include "SemaFixture.h"
+#include "swift/AST/Module.h"
+#include "swift/AST/ParseRequests.h"
+#include "swift/Strings.h"
+#include "swift/Subsystems.h"
+
+using namespace swift;
+using namespace swift::unittest;
+
+SemaTest::SemaTest()
+    : Context(*ASTContext::get(LangOpts, TypeCheckerOpts, SearchPathOpts,
+                               ClangImporterOpts, SourceMgr, Diags)) {
+  registerParseRequestFunctions(Context.evaluator);
+  registerTypeCheckerRequestFunctions(Context.evaluator);
+  auto stdlibID = Context.getIdentifier(STDLIB_NAME);
+  auto *module = ModuleDecl::create(stdlibID, Context);
+  Context.addLoadedModule(module);
+
+  FileForLookups = new (Context) SourceFile(*module, SourceFileKind::Library,
+                                            /*buffer*/ None);
+  module->addFile(*FileForLookups);
+
+  DC = module;
+}