Sema: Remove OneWayExpr and Builtin.one_way

Author: slavapestov

include/swift/AST/Expr.h

@@ -6413,33 +6413,6 @@ class SingleValueStmtExpr : public Expr {
   }
 };
 
-/// Expression node that effects a "one-way" constraint in
-/// the constraint system, allowing type information to flow from the
-/// subexpression outward but not the other way.
-///
-/// One-way expressions are generally implicit and synthetic, introduced by
-/// the type checker. However, there is a built-in expression of the
-/// form \c Builtin.one_way(x) that forms a one-way constraint coming out
-/// of expression `x` that can be used for testing purposes.
-class OneWayExpr : public Expr {
-  Expr *SubExpr;
-
-public:
-  /// Construct an implicit one-way expression from the given subexpression.
-  OneWayExpr(Expr *subExpr)
-     : Expr(ExprKind::OneWay, /*isImplicit=*/true), SubExpr(subExpr) { }
-
-  SourceLoc getLoc() const { return SubExpr->getLoc(); }
-  SourceRange getSourceRange() const { return SubExpr->getSourceRange(); }
-
-  Expr *getSubExpr() const { return SubExpr; }
-  void setSubExpr(Expr *subExpr) { SubExpr = subExpr; }
-
-  static bool classof(const Expr *E) {
-    return E->getKind() == ExprKind::OneWay;
-  }
-};
-
 class TypeJoinExpr final : public Expr,
                            private llvm::TrailingObjects<TypeJoinExpr, Expr *> {
   friend TrailingObjects;

include/swift/AST/ExprNodes.def

@@ -214,7 +214,6 @@ EXPR(KeyPath, Expr)
 EXPR(CurrentContextIsolation, Expr)
 EXPR(SingleValueStmt, Expr)
 UNCHECKED_EXPR(KeyPathDot, Expr)
-UNCHECKED_EXPR(OneWay, Expr)
 EXPR(Tap, Expr)
 UNCHECKED_EXPR(TypeJoin, Expr)
 EXPR(MacroExpansion, Expr)

lib/AST/ASTDumper.cpp

@@ -3339,12 +3339,6 @@ class PrintExpr : public ExprVisitor<PrintExpr, void, StringRef>,
     printFoot();
   }
 
-  void visitOneWayExpr(OneWayExpr *E, StringRef label) {
-    printCommon(E, "one_way_expr", label);
-    printRec(E->getSubExpr());
-    printFoot();
-  }
-
   void visitTapExpr(TapExpr *E, StringRef label) {
     printCommon(E, "tap_expr", label);
     printDeclRefField(E->getVar(), "var");

lib/AST/ASTPrinter.cpp

@@ -4884,10 +4884,6 @@ void PrintAST::visitCoerceExpr(CoerceExpr *expr) {
   printType(expr->getCastType());
 }
 
-void PrintAST::visitOneWayExpr(OneWayExpr *expr) {
-  llvm_unreachable("Not representable in source code");
-}
-
 void PrintAST::printClosure(AbstractClosureExpr *closure, CaptureListExpr *captureList) {
 
 }

lib/AST/ASTWalker.cpp

@@ -1332,18 +1332,6 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
     return E;
   }
 
-  Expr *visitOneWayExpr(OneWayExpr *E) {
-    if (auto oldSubExpr = E->getSubExpr()) {
-      if (auto subExpr = doIt(oldSubExpr)) {
-        E->setSubExpr(subExpr);
-      } else {
-        return nullptr;
-      }
-    }
-
-    return E;
-  }
-
   Expr *visitTapExpr(TapExpr *E) {
     if (auto oldSubExpr = E->getSubExpr()) {
       if (auto subExpr = doIt(oldSubExpr)) {

lib/AST/Expr.cpp

@@ -461,7 +461,6 @@ ConcreteDeclRef Expr::getReferencedDecl(bool stopAtParenExpr) const {
   NO_REFERENCE(KeyPath);
   NO_REFERENCE(KeyPathDot);
   PASS_THROUGH_REFERENCE(CurrentContextIsolation, getActor);
-  PASS_THROUGH_REFERENCE(OneWay, getSubExpr);
   NO_REFERENCE(Tap);
   NO_REFERENCE(TypeJoin);
   SIMPLE_REFERENCE(MacroExpansion, getMacroRef);
@@ -662,7 +661,6 @@ bool Expr::canAppendPostfixExpression(bool appendingPostfixOperator) const {
   case ExprKind::Error:
   case ExprKind::CodeCompletion:
   case ExprKind::LazyInitializer:
-  case ExprKind::OneWay:
     return false;
 
   case ExprKind::NilLiteral:
@@ -1037,7 +1035,6 @@ bool Expr::isValidParentOfTypeExpr(Expr *typeExpr) const {
   case ExprKind::ObjCSelector:
   case ExprKind::KeyPath:
   case ExprKind::KeyPathDot:
-  case ExprKind::OneWay:
   case ExprKind::Tap:
   case ExprKind::SingleValueStmt:
   case ExprKind::TypeJoin:

lib/Sema/CSApply.cpp

@@ -5469,11 +5469,6 @@ namespace {
       llvm_unreachable("Handled by the walker directly");
     }
 
-    Expr *visitOneWayExpr(OneWayExpr *E) {
-      auto type = simplifyType(cs.getType(E));
-      return coerceToType(E->getSubExpr(), type, cs.getConstraintLocator(E));
-    }
-
     Expr *visitTapExpr(TapExpr *E) {
       auto type = simplifyType(cs.getType(E));
 

lib/Sema/CSGen.cpp

@@ -3163,14 +3163,6 @@ namespace {
       llvm_unreachable("Handled by the walker directly");
     }
 
-    Type visitOneWayExpr(OneWayExpr *expr) {
-      auto locator = CS.getConstraintLocator(expr);
-      auto resultTypeVar = CS.createTypeVariable(locator, 0);
-      CS.addConstraint(ConstraintKind::OneWayEqual, resultTypeVar,
-                       CS.getType(expr->getSubExpr()), locator);
-      return resultTypeVar;
-    }
-
     Type visitTapExpr(TapExpr *expr) {
       DeclContext *varDC = expr->getVar()->getDeclContext();
       ASSERT(varDC != nullptr);
@@ -3333,7 +3325,6 @@ namespace {
                                JoinInout,
                                JoinMeta,
                                JoinNonexistent,
-                               OneWay,
     };
 
     static TypeOperation getTypeOperation(UnresolvedDotExpr *UDE,
@@ -3347,7 +3338,6 @@ namespace {
 
       return llvm::StringSwitch<TypeOperation>(
                  UDE->getName().getBaseIdentifier().str())
-          .Case("one_way", TypeOperation::OneWay)
           .Case("type_join", TypeOperation::Join)
           .Case("type_join_inout", TypeOperation::JoinInout)
           .Case("type_join_meta", TypeOperation::JoinMeta)
@@ -3361,7 +3351,6 @@ namespace {
 
       switch (op) {
       case TypeOperation::None:
-      case TypeOperation::OneWay:
         llvm_unreachable(
             "We should have a valid type operation at this point!");
 
@@ -3558,12 +3547,7 @@ namespace {
           auto typeOperation =
               ConstraintGenerator::getTypeOperation(UDE, CS.getASTContext());
 
-          if (typeOperation == ConstraintGenerator::TypeOperation::OneWay) {
-            // For a one-way constraint, create the OneWayExpr node.
-            auto *unaryArg = apply->getArgs()->getUnlabeledUnaryExpr();
-            assert(unaryArg);
-            expr = new (CS.getASTContext()) OneWayExpr(unaryArg);
-          } else if (typeOperation !=
+          if (typeOperation !=
                          ConstraintGenerator::TypeOperation::None) {
             // Handle the Builtin.type_join* family of calls by replacing
             // them with dot_self_expr of type_expr with the type being the