Sema: Replace early return with ASSERT

It seems that we end up with a null Type in one place in
StmtChecker::visitSwitchStmt(), so add a null check there,
and a FIXME to investigate further.

Author: slavapestov

lib/Sema/TypeCheckConstraints.cpp

@@ -1192,10 +1192,7 @@ TypeChecker::coerceToRValue(ASTContext &Context, Expr *expr,
                             llvm::function_ref<Type(Expr *)> getType,
                             llvm::function_ref<void(Expr *, Type)> setType) {
   Type exprTy = getType(expr);
-
-  // If expr has no type, just assume it's the right expr.
-  if (!exprTy)
-    return expr;
+  ASSERT(exprTy);
 
   // If the type is already materializable, then we're already done.
   if (!exprTy->hasLValueType())

lib/Sema/TypeCheckStmt.cpp

@@ -1702,6 +1702,11 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
     // Type-check the subject expression.
     Expr *subjectExpr = switchStmt->getSubjectExpr();
     auto resultTy = TypeChecker::typeCheckExpression(subjectExpr, DC);
+
+    // FIXME: What's happening here?
+    if (!resultTy)
+      return switchStmt;
+
     auto limitExhaustivityChecks = !resultTy;
     if (Expr *newSubjectExpr =
             TypeChecker::coerceToRValue(getASTContext(), subjectExpr))