Revert "[5.8] Introduce if/switch expressions"

Author: hamishknight

include/swift/AST/ASTScope.h

@@ -955,7 +955,6 @@ class PatternEntryInitializerScope final : public AbstractPatternEntryScope {
 
 protected:
   bool lookupLocalsOrMembers(DeclConsumer) const override;
-  bool isLabeledStmtLookupTerminator() const override;
 };
 
 /// The scope introduced by a conditional clause initializer in an

include/swift/AST/ASTTypeIDZone.def

@@ -26,7 +26,6 @@ SWIFT_TYPEID(Fingerprint)
 SWIFT_TYPEID(GenericSignature)
 SWIFT_TYPEID(ImplicitImportList)
 SWIFT_TYPEID(ImplicitMemberAction)
-SWIFT_TYPEID(IsSingleValueStmtResult)
 SWIFT_TYPEID(ParamSpecifier)
 SWIFT_TYPEID(PropertyWrapperAuxiliaryVariables)
 SWIFT_TYPEID(PropertyWrapperInitializerInfo)

include/swift/AST/ASTTypeIDs.h

@@ -41,7 +41,6 @@ class GenericParamList;
 class GenericSignature;
 class GenericTypeParamType;
 class InfixOperatorDecl;
-class IsSingleValueStmtResult;
 class IterableDeclContext;
 class ModuleDecl;
 struct ImplicitImportList;

include/swift/AST/CASTBridging.h

@@ -169,9 +169,6 @@ void *SwiftVarDecl_create(void *ctx, BridgedIdentifier _Nullable name,
                           void *initExpr, void *loc, _Bool isStatic,
                           _Bool isLet, void *dc);
 
-void *SingleValueStmtExpr_createWithWrappedBranches(void *ctx, void *S,
-                                                    void *DC, _Bool mustBeExpr);
-
 void *IfStmt_create(void *ctx, void *ifLoc, void *cond, void *_Nullable then,
                     void *_Nullable elseLoc, void *_Nullable elseStmt);
 

include/swift/AST/DiagnosticsSema.def

@@ -1080,29 +1080,6 @@ ERROR(ternary_expr_cases_mismatch,none,
       "result values in '? :' expression have mismatching types %0 and %1",
       (Type, Type))
 
-// Statements as expressions
-ERROR(single_value_stmt_branches_mismatch,none,
-      "branches have mismatching types %0 and %1",
-      (Type, Type))
-ERROR(single_value_stmt_out_of_place,none,
-      "'%0' may only be used as expression in return, throw, or as the source "
-      "of an assignment",
-      (StmtKind))
-ERROR(single_value_stmt_must_be_unlabeled,none,
-      "'%0' cannot have a jump label when used as expression",
-      (StmtKind))
-ERROR(if_expr_must_be_syntactically_exhaustive,none,
-      "'if' must have an unconditional 'else' to be used as expression",
-      ())
-ERROR(single_value_stmt_branch_must_end_in_throw,none,
-      "non-expression branch of '%0' expression may only end with a 'throw'",
-      (StmtKind))
-ERROR(cannot_jump_in_single_value_stmt,none,
-      "cannot '%0' in '%1' when used as expression",
-      (StmtKind, StmtKind))
-ERROR(effect_marker_on_single_value_stmt,none,
-      "'%0' may not be used on '%1' expression", (StringRef, StmtKind))
-
 ERROR(did_not_call_function_value,none,
       "function value was used as a property; add () to call it",
       ())

include/swift/AST/Expr.h

@@ -4350,10 +4350,6 @@ class OpaqueValueExpr : public Expr {
     Bits.OpaqueValueExpr.IsPlaceholder = isPlaceholder;
   }
 
-  static OpaqueValueExpr *
-  createImplicit(ASTContext &ctx, Type Ty, bool isPlaceholder = false,
-                 AllocationArena arena = AllocationArena::Permanent);
-
   /// Whether this opaque value expression represents a placeholder that
   /// is injected before type checking to act as a placeholder for some
   /// value to be specified later.
@@ -5969,63 +5965,6 @@ class KeyPathDotExpr : public Expr {
   }
 };
 
-/// An expression that may wrap a statement which produces a single value.
-class SingleValueStmtExpr : public Expr {
-public:
-  enum class Kind {
-    If, Switch
-  };
-
-private:
-  Stmt *S;
-  DeclContext *DC;
-
-  SingleValueStmtExpr(Stmt *S, DeclContext *DC)
-      : Expr(ExprKind::SingleValueStmt, /*isImplicit*/ true), S(S), DC(DC) {}
-
-public:
-  /// Creates a new SingleValueStmtExpr wrapping a statement.
-  static SingleValueStmtExpr *create(ASTContext &ctx, Stmt *S, DeclContext *DC);
-
-  /// Creates a new SingleValueStmtExpr wrapping a statement, and recursively
-  /// attempts to wrap any branches of that statement that can become single
-  /// value statement expressions.
-  ///
-  /// If \p mustBeExpr is true, branches will be eagerly wrapped even if they
-  /// may not be valid SingleValueStmtExprs (which Sema will later diagnose).
-  static SingleValueStmtExpr *createWithWrappedBranches(ASTContext &ctx,
-                                                        Stmt *S,
-                                                        DeclContext *DC,
-                                                        bool mustBeExpr);
-
-  /// Attempt to look through valid parent expressions to a child
-  /// SingleValueStmtExpr.
-  static SingleValueStmtExpr *tryDigOutSingleValueStmtExpr(Expr *E);
-
-  /// Retrieve the wrapped statement.
-  Stmt *getStmt() const { return S; }
-  void setStmt(Stmt *newS) { S = newS; }
-
-  /// Retrieve the kind of statement being wrapped.
-  Kind getStmtKind() const;
-
-  /// Retrieve the complete set of branches for the underlying statement.
-  ArrayRef<Stmt *> getBranches(SmallVectorImpl<Stmt *> &scratch) const;
-
-  /// Retrieve the single expression branches of the statement, excluding
-  /// branches that either have multiple expressions, or have statements.
-  ArrayRef<Expr *>
-  getSingleExprBranches(SmallVectorImpl<Expr *> &scratch) const;
-
-  DeclContext *getDeclContext() const { return DC; }
-
-  SourceRange getSourceRange() const;
-
-  static bool classof(const Expr *E) {
-    return E->getKind() == ExprKind::SingleValueStmt;
-  }
-};
-
 /// 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.
@@ -6059,10 +5998,6 @@ class TypeJoinExpr final : public Expr,
 
   DeclRefExpr *Var;
 
-  /// If this is joining the expression branches for a SingleValueStmtExpr,
-  /// this holds the expr node. Otherwise, it is \c nullptr.
-  SingleValueStmtExpr *SVE;
-
   size_t numTrailingObjects() const {
     return getNumElements();
   }
@@ -6071,34 +6006,11 @@ class TypeJoinExpr final : public Expr,
     return { getTrailingObjects<Expr *>(), getNumElements() };
   }
 
-  TypeJoinExpr(llvm::PointerUnion<DeclRefExpr *, TypeBase *> result,
-               ArrayRef<Expr *> elements, SingleValueStmtExpr *SVE);
-
-  static TypeJoinExpr *
-  createImpl(ASTContext &ctx,
-             llvm::PointerUnion<DeclRefExpr *, TypeBase *> varOrType,
-             ArrayRef<Expr *> elements,
-             AllocationArena arena = AllocationArena::Permanent,
-             SingleValueStmtExpr *SVE = nullptr);
+  TypeJoinExpr(DeclRefExpr *var, ArrayRef<Expr *> elements);
 
 public:
-  static TypeJoinExpr *
-  create(ASTContext &ctx, DeclRefExpr *var, ArrayRef<Expr *> exprs,
-         AllocationArena arena = AllocationArena::Permanent) {
-    return createImpl(ctx, var, exprs, arena);
-  }
-
-  static TypeJoinExpr *
-  create(ASTContext &ctx, Type joinType, ArrayRef<Expr *> exprs,
-         AllocationArena arena = AllocationArena::Permanent) {
-    return createImpl(ctx, joinType.getPointer(), exprs, arena);
-  }
-
-  /// Create a join for the branch types of a SingleValueStmtExpr.
-  static TypeJoinExpr *
-  forBranchesOfSingleValueStmtExpr(ASTContext &ctx, Type joinType,
-                                   SingleValueStmtExpr *SVE,
-                                   AllocationArena arena);
+  static TypeJoinExpr *create(ASTContext &ctx, DeclRefExpr *var,
+                              ArrayRef<Expr *> exprs);
 
   SourceLoc getLoc() const { return SourceLoc(); }
   SourceRange getSourceRange() const { return SourceRange(); }
@@ -6122,10 +6034,6 @@ class TypeJoinExpr final : public Expr,
     getMutableElements()[i] = E;
   }
 
-  /// If this is joining the expression branches for a SingleValueStmtExpr,
-  /// this returns the expr node. Otherwise, returns \c nullptr.
-  SingleValueStmtExpr *getSingleValueStmtExpr() const { return SVE; }
-
   unsigned getNumElements() const { return Bits.TypeJoinExpr.NumElements; }
 
   static bool classof(const Expr *E) {

include/swift/AST/ExprNodes.def

@@ -204,7 +204,6 @@ EXPR(LazyInitializer, Expr)
 EXPR(EditorPlaceholder, Expr)
 EXPR(ObjCSelector, Expr)
 EXPR(KeyPath, Expr)
-EXPR(SingleValueStmt, Expr)
 UNCHECKED_EXPR(KeyPathDot, Expr)
 UNCHECKED_EXPR(OneWay, Expr)
 EXPR(Tap, Expr)

include/swift/AST/Stmt.h

@@ -35,15 +35,13 @@ class ASTContext;
 class ASTWalker;
 class Decl;
 class DeclContext;
-class Evaluator;
 class Expr;
 class FuncDecl;
 class Pattern;
 class PatternBindingDecl;
 class VarDecl;
 class CaseStmt;
 class DoCatchStmt;
-class IsSingleValueStmtResult;
 class SwitchStmt;
 
 enum class StmtKind {
@@ -135,12 +133,7 @@ class alignas(8) Stmt : public ASTAllocated<Stmt> {
 
   SourceRange getSourceRange() const;
   SourceLoc TrailingSemiLoc;
-
-  /// Whether the statement can produce a single value, and as such may be
-  /// treated as an expression.
-  IsSingleValueStmtResult mayProduceSingleValue(Evaluator &eval) const;
-  IsSingleValueStmtResult mayProduceSingleValue(ASTContext &ctx) const;
-
+  
   /// isImplicit - Determines whether this statement was implicitly-generated,
   /// rather than explicitly written in the AST.
   bool isImplicit() const { return Bits.Stmt.Implicit; }
@@ -211,10 +204,6 @@ class BraceStmt final : public Stmt,
 
   ASTNode findAsyncNode();
 
-  /// If this brace is wrapping a single expression, returns it. Otherwise
-  /// returns \c nullptr.
-  Expr *getSingleExpressionElement() const;
-
   static bool classof(const Stmt *S) { return S->getKind() == StmtKind::Brace; }
 };
 
@@ -722,14 +711,7 @@ class IfStmt : public LabeledConditionalStmt {
 
   Stmt *getElseStmt() const { return Else; }
   void setElseStmt(Stmt *s) { Else = s; }
-
-  /// Retrieve the complete set of branches for this if statement, including
-  /// else if statements.
-  ArrayRef<Stmt *> getBranches(SmallVectorImpl<Stmt *> &scratch) const;
-
-  /// Whether the if statement has an unconditional \c else.
-  bool isSyntacticallyExhaustive() const;
-
+  
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Stmt *S) { return S->getKind() == StmtKind::If; }
 };
@@ -1301,10 +1283,7 @@ class SwitchStmt final : public LabeledStmt,
   AsCaseStmtRange getCases() const {
     return AsCaseStmtRange(getRawCases(), AsCaseStmtWithSkippingNonCaseStmts());
   }
-
-  /// Retrieve the complete set of branches for this switch statement.
-  ArrayRef<Stmt *> getBranches(SmallVectorImpl<Stmt *> &scratch) const;
-
+  
   static bool classof(const Stmt *S) {
     return S->getKind() == StmtKind::Switch;
   }