Sema: Remove some unreachable code from CSApply

I believe these code paths could only be reached by re-typechecking
invalid code in the old CSDiag implementation.

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -225,13 +225,6 @@ ERROR(cannot_apply_lvalue_binop_to_subelement,none,
 ERROR(cannot_apply_lvalue_binop_to_rvalue,none,
       "left side of mutating operator has immutable type %0", (Type))
 
-ERROR(cannot_subscript_base,none,
-      "cannot subscript a value of type %0",
-      (Type))
-
-ERROR(cannot_subscript_ambiguous_base,none,
-      "cannot subscript a value of incorrect or ambiguous type", ())
-
 ERROR(cannot_subscript_nil_literal,none,
       "cannot subscript a nil literal value", ())
 ERROR(conditional_cast_from_nil,none,

include/swift/AST/Expr.h

@@ -3122,24 +3122,9 @@ class LoadExpr : public ImplicitConversionExpr {
   static bool classof(const Expr *E) { return E->getKind() == ExprKind::Load; }
 };
 
-/// This is a conversion from an expression of UnresolvedType to an arbitrary
-/// other type, and from an arbitrary type to UnresolvedType.  This node does
-/// not appear in valid code, only in code involving diagnostics.
-class UnresolvedTypeConversionExpr : public ImplicitConversionExpr {
-public:
-  UnresolvedTypeConversionExpr(Expr *subExpr, Type type)
-  : ImplicitConversionExpr(ExprKind::UnresolvedTypeConversion, subExpr, type) {}
-
-  static bool classof(const Expr *E) {
-    return E->getKind() == ExprKind::UnresolvedTypeConversion;
-  }
-};
-
 /// FunctionConversionExpr - Convert a function to another function type,
 /// which might involve renaming the parameters or handling substitutions
 /// of subtypes (in the return) or supertypes (in the input).
-///
-/// FIXME: This should be a CapturingExpr.
 class FunctionConversionExpr : public ImplicitConversionExpr {
 public:
   FunctionConversionExpr(Expr *subExpr, Type type)

include/swift/AST/ExprNodes.def

@@ -150,7 +150,6 @@ ABSTRACT_EXPR(Apply, Expr)
 ABSTRACT_EXPR(ImplicitConversion, Expr)
   EXPR(Load, ImplicitConversionExpr)
   EXPR(DestructureTuple, ImplicitConversionExpr)
-  EXPR(UnresolvedTypeConversion, ImplicitConversionExpr)
   EXPR(FunctionConversion, ImplicitConversionExpr)
   EXPR(CovariantFunctionConversion, ImplicitConversionExpr)
   EXPR(CovariantReturnConversion, ImplicitConversionExpr)

lib/AST/ASTDumper.cpp

@@ -2267,11 +2267,6 @@ class PrintExpr : public ExprVisitor<PrintExpr> {
     printRec(E->getResultExpr());
     PrintWithColorRAII(OS, ParenthesisColor) << ')';
   }
-  void visitUnresolvedTypeConversionExpr(UnresolvedTypeConversionExpr *E) {
-    printCommon(E, "unresolvedtype_conversion_expr") << '\n';
-    printRec(E->getSubExpr());
-    PrintWithColorRAII(OS, ParenthesisColor) << ')';
-  }
   void visitFunctionConversionExpr(FunctionConversionExpr *E) {
     printCommon(E, "function_conversion_expr") << '\n';
     printRec(E->getSubExpr());

lib/AST/Expr.cpp

@@ -337,7 +337,6 @@ ConcreteDeclRef Expr::getReferencedDecl(bool stopAtParenExpr) const {
 
   PASS_THROUGH_REFERENCE(Load, getSubExpr);
   NO_REFERENCE(DestructureTuple);
-  NO_REFERENCE(UnresolvedTypeConversion);
   PASS_THROUGH_REFERENCE(FunctionConversion, getSubExpr);
   PASS_THROUGH_REFERENCE(CovariantFunctionConversion, getSubExpr);
   PASS_THROUGH_REFERENCE(CovariantReturnConversion, getSubExpr);
@@ -661,7 +660,6 @@ bool Expr::canAppendPostfixExpression(bool appendingPostfixOperator) const {
 
   case ExprKind::Load:
   case ExprKind::DestructureTuple:
-  case ExprKind::UnresolvedTypeConversion:
   case ExprKind::FunctionConversion:
   case ExprKind::CovariantFunctionConversion:
   case ExprKind::CovariantReturnConversion:

lib/SILGen/SILGenExpr.cpp

@@ -447,8 +447,6 @@ namespace {
     RValue visitConditionalBridgeFromObjCExpr(ConditionalBridgeFromObjCExpr *E,
                                               SGFContext C);
     RValue visitArchetypeToSuperExpr(ArchetypeToSuperExpr *E, SGFContext C);
-    RValue visitUnresolvedTypeConversionExpr(UnresolvedTypeConversionExpr *E,
-                                             SGFContext C);
     RValue visitFunctionConversionExpr(FunctionConversionExpr *E,
                                        SGFContext C);
     RValue visitCovariantFunctionConversionExpr(
@@ -957,12 +955,6 @@ RValue RValueEmitter::visitSuperRefExpr(SuperRefExpr *E, SGFContext C) {
   return RValue(SGF, E, result);
 }
 
-RValue RValueEmitter::
-visitUnresolvedTypeConversionExpr(UnresolvedTypeConversionExpr *E,
-                                  SGFContext C) {
-  llvm_unreachable("invalid code made its way into SILGen");
-}
-
 RValue RValueEmitter::visitOtherConstructorDeclRefExpr(
                                 OtherConstructorDeclRefExpr *E, SGFContext C) {
   // This should always be a child of an ApplyExpr and so will be emitted by

lib/Sema/CSApply.cpp

@@ -2679,8 +2679,7 @@ namespace {
       auto type = simplifyType(openedType);
       cs.setType(expr, type);
 
-      if (type->is<UnresolvedType>())
-        return expr;
+      assert(!type->is<UnresolvedType>());
 
       auto &ctx = cs.getASTContext();
 
@@ -2703,14 +2702,11 @@ namespace {
       ConcreteDeclRef witness = conformance.getWitnessByName(
           conformingType->getRValueType(), constrName);
 
-      auto selectedOverload = solution.getOverloadChoiceIfAvailable(
+      auto selectedOverload = solution.getOverloadChoice(
           cs.getConstraintLocator(expr, ConstraintLocator::ConstructorMember));
 
-      if (!selectedOverload)
-        return nullptr;
-
       auto fnType =
-          simplifyType(selectedOverload->openedType)->castTo<FunctionType>();
+          simplifyType(selectedOverload.openedType)->castTo<FunctionType>();
 
       auto newArg = coerceCallArguments(
           expr->getArg(), fnType, witness,
@@ -3009,18 +3005,8 @@ namespace {
       // Determine the declaration selected for this overloaded reference.
       auto memberLocator = cs.getConstraintLocator(expr,
                                                    ConstraintLocator::Member);
-      auto selectedElt = solution.getOverloadChoiceIfAvailable(memberLocator);
-
-      if (!selectedElt) {
-        // If constraint solving resolved this to an UnresolvedType, then we're
-        // in an ambiguity tolerant mode used for diagnostic generation.  Just
-        // leave this as whatever type of member reference it already is.
-        Type resultTy = simplifyType(cs.getType(expr));
-        cs.setType(expr, resultTy);
-        return expr;
-      }
+      auto selected = solution.getOverloadChoice(memberLocator);
 
-      auto selected = *selectedElt;
       if (!selected.choice.getBaseType()) {
         // This is one of the "outer alternatives", meaning the innermost
         // methods didn't work out.
@@ -3252,40 +3238,19 @@ namespace {
     Expr *visitSubscriptExpr(SubscriptExpr *expr) {
       auto *memberLocator =
           cs.getConstraintLocator(expr, ConstraintLocator::SubscriptMember);
-      auto overload = solution.getOverloadChoiceIfAvailable(memberLocator);
-
-      // Handles situation where there was a solution available but it didn't
-      // have a proper overload selected from subscript call, might be because
-      // solver was allowed to return free or unresolved types, which can
-      // happen while running diagnostics on one of the expressions.
-      if (!overload) {
-        auto *base = expr->getBase();
-        auto &de = cs.getASTContext().Diags;
-        auto baseType = cs.getType(base);
-
-        if (auto errorType = baseType->getAs<ErrorType>()) {
-          de.diagnose(base->getLoc(), diag::cannot_subscript_base,
-                      errorType->getOriginalType())
-              .highlight(base->getSourceRange());
-        } else {
-          de.diagnose(base->getLoc(), diag::cannot_subscript_ambiguous_base)
-              .highlight(base->getSourceRange());
-        }
-
-        return nullptr;
-      }
+      auto overload = solution.getOverloadChoice(memberLocator);
 
-      if (overload->choice.getKind() ==
+      if (overload.choice.getKind() ==
               OverloadChoiceKind::KeyPathDynamicMemberLookup) {
         return buildDynamicMemberLookupRef(
             expr, expr->getBase(), expr->getIndex()->getStartLoc(), SourceLoc(),
-            *overload, memberLocator);
+            overload, memberLocator);
       }
 
       return buildSubscript(
           expr->getBase(), expr->getIndex(), expr->getArgumentLabels(),
           expr->hasTrailingClosure(), cs.getConstraintLocator(expr),
-          expr->isImplicit(), expr->getAccessSemantics(), *overload);
+          expr->isImplicit(), expr->getAccessSemantics(), overload);
     }
 
     /// "Finish" an array expression by filling in the semantic expression.
@@ -4146,8 +4111,7 @@ namespace {
       expr->getSubPattern()->forEachVariable([](VarDecl *VD) {
         VD->setInvalid();
       });
-      if (!SuppressDiagnostics
-          && !cs.getType(simplified)->is<UnresolvedType>()) {
+      if (!SuppressDiagnostics) {
         auto &de = cs.getASTContext().Diags;
         de.diagnose(simplified->getLoc(), diag::pattern_in_expr,
                     expr->getSubPattern()->getKind());
@@ -4626,18 +4590,12 @@ namespace {
         // If this is an unresolved link, make sure we resolved it.
         if (kind == KeyPathExpr::Component::Kind::UnresolvedProperty ||
             kind == KeyPathExpr::Component::Kind::UnresolvedSubscript) {
-          auto foundDecl = solution.getOverloadChoiceIfAvailable(locator);
-          if (!foundDecl) {
-            // If we couldn't resolve the component, leave it alone.
-            resolvedComponents.push_back(origComponent);
-            componentTy = origComponent.getComponentType();
-            continue;
-          }
+          auto foundDecl = solution.getOverloadChoice(locator);
 
           isDynamicMember =
-              foundDecl->choice.getKind() ==
+              foundDecl.choice.getKind() ==
                   OverloadChoiceKind::DynamicMemberLookup ||
-              foundDecl->choice.getKind() ==
+              foundDecl.choice.getKind() ==
                   OverloadChoiceKind::KeyPathDynamicMemberLookup;
 
           // If this was a @dynamicMemberLookup property, then we actually
@@ -4668,11 +4626,9 @@ namespace {
         case KeyPathExpr::Component::Kind::OptionalChain: {
           didOptionalChain = true;
           // Chaining always forces the element to be an rvalue.
+          assert(!componentTy->hasUnresolvedType());
           auto objectTy =
               componentTy->getWithoutSpecifierType()->getOptionalObjectType();
-          if (componentTy->hasUnresolvedType() && !objectTy) {
-            objectTy = componentTy;
-          }
           assert(objectTy);
 
           auto loc = origComponent.getLoc();
@@ -4724,8 +4680,8 @@ namespace {
       }
 
       // Wrap a non-optional result if there was chaining involved.
+      assert(!componentTy->hasUnresolvedType());
       if (didOptionalChain && componentTy &&
-          !componentTy->hasUnresolvedType() &&
           !componentTy->getWithoutSpecifierType()->isEqual(leafTy)) {
         assert(leafTy->getOptionalObjectType()->isEqual(
             componentTy->getWithoutSpecifierType()));
@@ -4744,8 +4700,8 @@ namespace {
 
       // The final component type ought to line up with the leaf type of the
       // key path.
-      assert(!componentTy || componentTy->hasUnresolvedType()
-             || componentTy->getWithoutSpecifierType()->isEqual(leafTy));
+      assert(!componentTy->hasUnresolvedType());
+      assert(componentTy->getWithoutSpecifierType()->isEqual(leafTy));
 
       if (!isFunctionType)
         return E;
@@ -4850,18 +4806,13 @@ namespace {
 
       // Unwrap the last component type, preserving @lvalue-ness.
       auto optionalTy = components.back().getComponentType();
+      assert(!optionalTy->hasUnresolvedType());
       Type objectTy;
       if (auto lvalue = optionalTy->getAs<LValueType>()) {
         objectTy = lvalue->getObjectType()->getOptionalObjectType();
-        if (optionalTy->hasUnresolvedType() && !objectTy) {
-          objectTy = optionalTy;
-        }
         objectTy = LValueType::get(objectTy);
       } else {
         objectTy = optionalTy->getOptionalObjectType();
-        if (optionalTy->hasUnresolvedType() && !objectTy) {
-          objectTy = optionalTy;
-        }
       }
       assert(objectTy);
 
@@ -5290,11 +5241,9 @@ Expr *ExprRewriter::coerceExistential(Expr *expr, Type toType) {
   Type toInstanceType = toType;
 
   // Look through metatypes
-  while ((fromInstanceType->is<UnresolvedType>() ||
-          fromInstanceType->is<AnyMetatypeType>()) &&
+  while (fromInstanceType->is<AnyMetatypeType>() &&
          toInstanceType->is<ExistentialMetatypeType>()) {
-    if (!fromInstanceType->is<UnresolvedType>())
-      fromInstanceType = fromInstanceType->castTo<AnyMetatypeType>()->getInstanceType();
+    fromInstanceType = fromInstanceType->castTo<AnyMetatypeType>()->getInstanceType();
     toInstanceType = toInstanceType->castTo<ExistentialMetatypeType>()->getInstanceType();
   }
 
@@ -5492,11 +5441,6 @@ Expr *ExprRewriter::coerceCallArguments(
         LocatorPathElt::ApplyArgToParam(argIdx, paramIdx, flags));
   };
 
-  bool matchCanFail =
-      llvm::any_of(params, [](const AnyFunctionType::Param &param) {
-        return param.getPlainType()->hasUnresolvedType();
-      });
-
   // Determine whether this application has curried self.
   bool skipCurriedSelf = apply ? hasCurriedSelf(cs, callee, apply) : true;
   // Determine the parameter bindings.
@@ -5554,9 +5498,7 @@ Expr *ExprRewriter::coerceCallArguments(
       args, params, paramInfo, unlabeledTrailingClosureIndex,
       /*allowFixes=*/false, listener, trailingClosureMatching);
 
-  assert((matchCanFail || callArgumentMatch) &&
-         "Call arguments did not match up?");
-  (void)matchCanFail;
+  assert(callArgumentMatch && "Call arguments did not match up?");
 
   auto parameterBindings = std::move(callArgumentMatch->parameterBindings);
 
@@ -6279,8 +6221,7 @@ Expr *ExprRewriter::coerceToType(Expr *expr, Type toType,
   if (knownRestriction != solution.ConstraintRestrictions.end()) {
     switch (knownRestriction->second) {
     case ConversionRestrictionKind::DeepEquality: {
-      if (toType->hasUnresolvedType())
-        break;
+      assert(!toType->hasUnresolvedType());
 
       // HACK: Fix problem related to Swift 4 mode (with assertions),
       // since Swift 4 mode allows passing arguments with extra parens
@@ -6826,9 +6767,8 @@ Expr *ExprRewriter::coerceToType(Expr *expr, Type toType,
     break;
   }
 
-  // Unresolved types come up in diagnostics for lvalue and inout types.
-  if (fromType->hasUnresolvedType() || toType->hasUnresolvedType())
-    return cs.cacheType(new (ctx) UnresolvedTypeConversionExpr(expr, toType));
+  assert(!fromType->hasUnresolvedType());
+  assert(!toType->hasUnresolvedType());
 
   // Use an opaque type to abstract a value of the underlying concrete type.
   if (toType->getAs<OpaqueTypeArchetypeType>()) {
@@ -7401,19 +7341,14 @@ Expr *ExprRewriter::finishApply(ApplyExpr *apply, Type openedType,
   // FIXME: handle unwrapping everywhere else
   assert(!unwrapResult);
 
-  // If this is an UnresolvedType in the system, preserve it.
-  if (cs.getType(fn)->is<UnresolvedType>()) {
-    cs.setType(apply, cs.getType(fn));
-    return apply;
-  }
+  assert(!cs.getType(fn)->is<UnresolvedType>());
 
   // We have a type constructor.
   auto metaTy = cs.getType(fn)->castTo<AnyMetatypeType>();
   auto ty = metaTy->getInstanceType();
 
   // If we're "constructing" a tuple type, it's simply a conversion.
   if (auto tupleTy = ty->getAs<TupleType>()) {
-    // FIXME: Need an AST to represent this properly.
     return coerceToType(apply->getArg(), tupleTy, locator);
   }
 
@@ -7422,19 +7357,14 @@ Expr *ExprRewriter::finishApply(ApplyExpr *apply, Type openedType,
   auto *ctorLocator =
       cs.getConstraintLocator(locator, {ConstraintLocator::ApplyFunction,
                                         ConstraintLocator::ConstructorMember});
-  auto selected = solution.getOverloadChoiceIfAvailable(ctorLocator);
-  if (!selected) {
-    assert(ty->hasError() || ty->hasUnresolvedType());
-    cs.setType(apply, ty);
-    return apply;
-  }
+  auto selected = solution.getOverloadChoice(ctorLocator);
 
   assert(ty->getNominalOrBoundGenericNominal() || ty->is<DynamicSelfType>() ||
          ty->isExistentialType() || ty->is<ArchetypeType>());
 
   // Consider the constructor decl reference expr 'implicit', but the
   // constructor call expr itself has the apply's 'implicitness'.
-  Expr *declRef = buildMemberRef(fn, /*dotLoc=*/SourceLoc(), *selected,
+  Expr *declRef = buildMemberRef(fn, /*dotLoc=*/SourceLoc(), selected,
                                  DeclNameLoc(fn->getEndLoc()), locator,
                                  ctorLocator, /*implicit=*/true,
                                  AccessSemantics::Ordinary);