Merge pull request swiftlang#71123 from hamishknight/sema-expr-return

Move the single-expr return transform from Parse to Sema

Author: hamishknight

include/swift/AST/AnyFunctionRef.h

@@ -94,18 +94,6 @@ class AnyFunctionRef {
     return !TheFunction.get<AbstractClosureExpr *>()->getType().isNull();
   }
 
-  bool hasSingleExpressionBody() const {
-    if (auto *AFD = TheFunction.dyn_cast<AbstractFunctionDecl *>())
-      return AFD->hasSingleExpressionBody();
-    return TheFunction.get<AbstractClosureExpr *>()->hasSingleExpressionBody();
-  }
-
-  Expr *getSingleExpressionBody() const {
-    if (auto *AFD = TheFunction.dyn_cast<AbstractFunctionDecl *>())
-      return AFD->getSingleExpressionBody();
-    return TheFunction.get<AbstractClosureExpr *>()->getSingleExpressionBody();
-  }
-
   ParameterList *getParameters() const {
     if (auto *AFD = TheFunction.dyn_cast<AbstractFunctionDecl *>())
       return AFD->getParameters();
@@ -152,33 +140,31 @@ class AnyFunctionRef {
     return cast<AutoClosureExpr>(ACE)->getBody();
   }
 
-  void setParsedBody(BraceStmt *stmt, bool isSingleExpression) {
+  void setParsedBody(BraceStmt *stmt) {
     if (auto *AFD = TheFunction.dyn_cast<AbstractFunctionDecl *>()) {
       AFD->setBody(stmt, AbstractFunctionDecl::BodyKind::Parsed);
-      AFD->setHasSingleExpressionBody(isSingleExpression);
       return;
     }
 
     auto *ACE = TheFunction.get<AbstractClosureExpr *>();
     if (auto *CE = dyn_cast<ClosureExpr>(ACE)) {
-      CE->setBody(stmt, isSingleExpression);
+      CE->setBody(stmt);
       CE->setBodyState(ClosureExpr::BodyState::ReadyForTypeChecking);
       return;
     }
 
     llvm_unreachable("autoclosures don't have statement bodies");
   }
 
-  void setTypecheckedBody(BraceStmt *stmt, bool isSingleExpression) {
+  void setTypecheckedBody(BraceStmt *stmt) {
     if (auto *AFD = TheFunction.dyn_cast<AbstractFunctionDecl *>()) {
       AFD->setBody(stmt, AbstractFunctionDecl::BodyKind::TypeChecked);
-      AFD->setHasSingleExpressionBody(isSingleExpression);
       return;
     }
 
     auto *ACE = TheFunction.get<AbstractClosureExpr *>();
     if (auto *CE = dyn_cast<ClosureExpr>(ACE)) {
-      CE->setBody(stmt, isSingleExpression);
+      CE->setBody(stmt);
       CE->setBodyState(ClosureExpr::BodyState::TypeCheckedWithSignature);
       return;
     }

include/swift/AST/Decl.h

@@ -464,7 +464,7 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   SWIFT_INLINE_BITFIELD(SubscriptDecl, VarDecl, 2,
     StaticSpelling : 2
   );
-  SWIFT_INLINE_BITFIELD(AbstractFunctionDecl, ValueDecl, 3+2+2+2+8+1+1+1+1+1+1+1,
+  SWIFT_INLINE_BITFIELD(AbstractFunctionDecl, ValueDecl, 3+2+2+2+8+1+1+1+1+1+1,
     /// \see AbstractFunctionDecl::BodyKind
     BodyKind : 3,
 
@@ -492,9 +492,6 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
     /// Whether the function body throws.
     Throws : 1,
 
-    /// Whether this member's body consists of a single expression.
-    HasSingleExpressionBody : 1,
-
     /// Whether peeking into this function detected nested type declarations.
     /// This is set when skipping over the decl at parsing.
     HasNestedTypeDeclarations : 1,
@@ -7177,7 +7174,6 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
     Bits.AbstractFunctionDecl.Overridden = false;
     Bits.AbstractFunctionDecl.Async = Async;
     Bits.AbstractFunctionDecl.Throws = Throws;
-    Bits.AbstractFunctionDecl.HasSingleExpressionBody = false;
     Bits.AbstractFunctionDecl.HasNestedTypeDeclarations = false;
     Bits.AbstractFunctionDecl.DistributedThunk = false;
   }
@@ -7211,17 +7207,6 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
   }
 
 public:
-  void setHasSingleExpressionBody(bool Has = true) { 
-    Bits.AbstractFunctionDecl.HasSingleExpressionBody = Has;
-  }
-
-  bool hasSingleExpressionBody() const {
-    return Bits.AbstractFunctionDecl.HasSingleExpressionBody;
-  }
-
-  Expr *getSingleExpressionBody() const;
-  void setSingleExpressionBody(Expr *NewBody);
-
   /// Returns the string for the base name, or "_" if this is unnamed.
   StringRef getNameStr() const {
     assert(!getName().isSpecial() && "Cannot get string for special names");

include/swift/AST/Expr.h

@@ -3591,6 +3591,22 @@ class ArchetypeToSuperExpr : public ImplicitConversionExpr {
   }
 };
 
+/// An expression that models an implicit conversion from an uninhabited value
+/// to any type. It cannot be evaluated.
+class UnreachableExpr : public ImplicitConversionExpr {
+  UnreachableExpr(Expr *subExpr, Type ty)
+      : ImplicitConversionExpr(ExprKind::Unreachable, subExpr, ty) {}
+
+public:
+  static UnreachableExpr *create(ASTContext &ctx, Expr *subExpr, Type ty) {
+    return new (ctx) UnreachableExpr(subExpr, ty);
+  }
+
+  static bool classof(const Expr *E) {
+    return E->getKind() == ExprKind::Unreachable;
+  }
+};
+
 /// The builtin unary '&' operator, which converts the
 /// given lvalue into an 'inout' argument value.
 class InOutExpr : public Expr {
@@ -3927,9 +3943,7 @@ class AbstractClosureExpr : public DeclContext, public Expr {
   bool hasSingleExpressionBody() const;
 
   /// Retrieve the body for closure that has a single expression for
-  /// its body.
-  ///
-  /// Only valid when \c hasSingleExpressionBody() is true.
+  /// its body, or \c nullptr if there is no single expression body.
   Expr *getSingleExpressionBody() const;
 
   /// Returns the body of closures that have a body
@@ -4055,9 +4069,9 @@ class ClosureExpr : public AbstractClosureExpr {
   /// The explicitly-specified result type.
   llvm::PointerIntPair<TypeExpr *, 2, BodyState> ExplicitResultTypeAndBodyState;
 
-  /// The body of the closure, along with a bit indicating whether it
-  /// was originally just a single expression.
-  llvm::PointerIntPair<BraceStmt *, 1, bool> Body;
+  /// The body of the closure.
+  BraceStmt *Body;
+
 public:
   ClosureExpr(const DeclAttributes &attributes,
               SourceRange bracketRange, VarDecl *capturedSelfDecl,
@@ -4083,11 +4097,8 @@ class ClosureExpr : public AbstractClosureExpr {
   SourceLoc getEndLoc() const;
   SourceLoc getLoc() const;
 
-  BraceStmt *getBody() const { return Body.getPointer(); }
-  void setBody(BraceStmt *S, bool isSingleExpression) {
-    Body.setPointer(S);
-    Body.setInt(isSingleExpression);
-  }
+  BraceStmt *getBody() const { return Body; }
+  void setBody(BraceStmt *S) { Body = S; }
 
   DeclAttributes &getAttrs() { return Attributes; }
   const DeclAttributes &getAttrs() const { return Attributes; }
@@ -4202,13 +4213,11 @@ class ClosureExpr : public AbstractClosureExpr {
   /// ... even if the closure has been coerced to return Void by the type
   /// checker. This function does not return true for empty closures.
   bool hasSingleExpressionBody() const {
-    return Body.getInt();
+    return getSingleExpressionBody();
   }
 
   /// Retrieve the body for closure that has a single expression for
-  /// its body.
-  ///
-  /// Only valid when \c hasSingleExpressionBody() is true.
+  /// its body, or \c nullptr if there is no single expression body.
   Expr *getSingleExpressionBody() const;
 
   /// Is this a completely empty closure?

include/swift/AST/ExprNodes.def

@@ -183,6 +183,7 @@ ABSTRACT_EXPR(ImplicitConversion, Expr)
   EXPR(ForeignObjectConversion, ImplicitConversionExpr)
   EXPR(UnevaluatedInstance, ImplicitConversionExpr)
   EXPR(UnderlyingToOpaque, ImplicitConversionExpr)
+  EXPR(Unreachable, ImplicitConversionExpr)
   EXPR(DifferentiableFunction, ImplicitConversionExpr)
   EXPR(LinearFunction, ImplicitConversionExpr)
   EXPR(DifferentiableFunctionExtractOriginal, ImplicitConversionExpr)

include/swift/AST/Stmt.h

@@ -99,6 +99,12 @@ class alignas(8) Stmt : public ASTAllocated<Stmt> {
     : NumPadBits,
     CaseCount : 32
   );
+    
+  SWIFT_INLINE_BITFIELD(ReturnStmt, Stmt, 1,
+    /// Whether the result is an implied return, e.g for an implicit single
+    /// expression return.
+    IsImplied : 1
+  );
 
   SWIFT_INLINE_BITFIELD_FULL(YieldStmt, Stmt, 32,
     : NumPadBits,
@@ -244,7 +250,9 @@ class ReturnStmt : public Stmt {
 
   ReturnStmt(SourceLoc returnLoc, Expr *result, bool isImplicit)
       : Stmt(StmtKind::Return, isImplicit), ReturnLoc(returnLoc),
-        Result(result) {}
+        Result(result) {
+    Bits.ReturnStmt.IsImplied = false;
+  }
 
 public:
   static ReturnStmt *createParsed(ASTContext &ctx, SourceLoc returnLoc,
@@ -261,11 +269,25 @@ class ReturnStmt : public Stmt {
     return createImplicit(ctx, SourceLoc(), result);
   }
 
+  /// Create an implicit implied ReturnStmt for a single expression body.
+  static ReturnStmt *forSingleExprBody(ASTContext &ctx, Expr *result) {
+    assert(result && "Result must be present to be implied");
+    auto *RS = createImplicit(ctx, result);
+    RS->Bits.ReturnStmt.IsImplied = true;
+    return RS;
+  }
+
   SourceLoc getReturnLoc() const { return ReturnLoc; }
 
   SourceLoc getStartLoc() const;
   SourceLoc getEndLoc() const;
 
+  /// Whether the result is an implied return, e.g for an implicit single
+  /// expression return.
+  bool isImplied() const {
+    return Bits.ReturnStmt.IsImplied;
+  }
+
   bool hasResult() const { return Result != 0; }
   Expr *getResult() const {
     assert(Result && "ReturnStmt doesn't have a result");

include/swift/AST/TypeCheckRequests.h

@@ -4128,9 +4128,9 @@ class PreCheckReturnStmtRequest
   bool isCached() const { return true; }
 };
 
-/// Performs some pre-checking of a function body, including inserting and
-/// removing implict returns where needed. This request is currently
-/// side-effectful, as it will mutate the body in-place.
+/// Performs some pre-checking of a function body, including inserting implicit
+/// returns where needed. This request is currently side-effectful, as it will
+/// mutate the body in-place.
 ///
 /// Note this request is currently uncached as:
 /// - The result will ultimately be cached by TypeCheckFunctionBodyRequest.
@@ -4152,6 +4152,23 @@ class PreCheckFunctionBodyRequest
   BraceStmt *evaluate(Evaluator &evaluator, AbstractFunctionDecl *AFD) const;
 };
 
+/// Performs some pre-checking of a closure's body, including inserting implicit
+/// returns where needed. This request is currently side-effectful, as it will
+/// mutate the body in-place. Like PreCheckFunctionBodyRequest, it is currently
+/// uncached.
+class PreCheckClosureBodyRequest
+    : public SimpleRequest<PreCheckClosureBodyRequest,
+                           BraceStmt *(ClosureExpr *),
+                           RequestFlags::Uncached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  BraceStmt *evaluate(Evaluator &evaluator, ClosureExpr *closure) const;
+};
+
 /// The result of the query for whether a statement can produce a single value.
 class IsSingleValueStmtResult {
 public:

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -350,6 +350,9 @@ SWIFT_REQUEST(TypeChecker, TangentStoredPropertyRequest,
 SWIFT_REQUEST(TypeChecker, PreCheckFunctionBodyRequest,
               BraceStmt *(AbstractFunctionDecl *),
               Uncached, NoLocationInfo)
+SWIFT_REQUEST(TypeChecker, PreCheckClosureBodyRequest,
+              BraceStmt *(ClosureExpr *),
+              Uncached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, TypeCheckFunctionBodyRequest,
               BraceStmt *(AbstractFunctionDecl *), SeparatelyCached,
               NoLocationInfo)

include/swift/Sema/CompletionContextFinder.h

@@ -73,12 +73,6 @@ class CompletionContextFinder : public ASTWalker {
 
   PostWalkResult<Expr *> walkToExprPost(Expr *E) override;
 
-  /// Check whether code completion expression is located inside of a
-  /// multi-statement closure.
-  bool locatedInMultiStmtClosure() const {
-    return hasContext(ContextKind::MultiStmtClosure);
-  }
-
   bool locatedInStringInterpolation() const {
     return hasContext(ContextKind::StringInterpolation);
   }

include/swift/Sema/ConstraintLocator.h

@@ -47,16 +47,17 @@ class ProtocolConformance;
 /// specified error messages when the conversion fails.
 ///
 enum ContextualTypePurpose : uint8_t {
-  CTP_Unused,           ///< No contextual type is specified.
-  CTP_Initialization,   ///< Pattern binding initialization.
-  CTP_ReturnStmt,       ///< Value specified to a 'return' statement.
-  CTP_ReturnSingleExpr, ///< Value implicitly returned from a function.
-  CTP_YieldByValue,     ///< By-value yield operand.
-  CTP_YieldByReference, ///< By-reference yield operand.
-  CTP_ThrowStmt,        ///< Value specified to a 'throw' statement.
-  CTP_DiscardStmt,      ///< Value specified to a 'discard' statement.
-  CTP_EnumCaseRawValue, ///< Raw value specified for "case X = 42" in enum.
-  CTP_DefaultParameter, ///< Default value in parameter 'foo(a : Int = 42)'.
+  CTP_Unused,            ///< No contextual type is specified.
+  CTP_Initialization,    ///< Pattern binding initialization.
+  CTP_ReturnStmt,        ///< Value specified to a 'return' statement.
+  CTP_ImpliedReturnStmt, ///< Value from an implied 'return', e.g a single expr
+                         ///  function body.
+  CTP_YieldByValue,      ///< By-value yield operand.
+  CTP_YieldByReference,  ///< By-reference yield operand.
+  CTP_ThrowStmt,         ///< Value specified to a 'throw' statement.
+  CTP_DiscardStmt,       ///< Value specified to a 'discard' statement.
+  CTP_EnumCaseRawValue,  ///< Raw value specified for "case X = 42" in enum.
+  CTP_DefaultParameter,  ///< Default value in parameter 'foo(a : Int = 42)'.
 
   /// Default value in @autoclosure parameter
   /// 'foo(a : @autoclosure () -> Int = 42)'.
@@ -819,11 +820,13 @@ class LocatorPathElt::TypeParameterRequirement final
 
 class LocatorPathElt::ClosureBody final : public StoredIntegerElement<1> {
   public:
-  ClosureBody(bool hasExplicitReturn = false)
-    : StoredIntegerElement(ConstraintLocator::ClosureBody, hasExplicitReturn) {}
+  ClosureBody(bool hasImpliedReturn)
+    : StoredIntegerElement(ConstraintLocator::ClosureBody, hasImpliedReturn) {}
 
-  /// Indicates whether body of the closure has any `return` statements.
-  bool hasExplicitReturn() const { return bool(getValue()); }
+  /// Indicates whether body of the closure has an implied `return` statement,
+  /// this is the case for single expression bodies where the `return` was not
+  /// written explicitly.
+  bool hasImpliedReturn() const { return bool(getValue()); }
 
   static bool classof(const LocatorPathElt *elt) {
     return elt->getKind() == ConstraintLocator::ClosureBody;

lib/AST/ASTBridging.cpp

@@ -1019,7 +1019,7 @@ BridgedClosureExpr_createParsed(BridgedASTContext cContext,
   auto *out = new (context) ClosureExpr(
       attributes, bracketRange, nullptr, nullptr, asyncLoc, throwsLoc,
       /*FIXME:thrownType=*/nullptr, arrowLoc, inLoc, nullptr, declContext);
-  out->setBody(body.unbridged(), true);
+  out->setBody(body.unbridged());
   out->setParameterList(params);
   return out;
 }