[AST] CaptureListExpr's body is always a ClosureExpr (#7326)

Author: jtbandes

include/swift/AST/Expr.h

@@ -3256,48 +3256,6 @@ class SequenceExpr final : public Expr,
 };
 
 
-/// Instances of this structure represent elements of the capture list that can
-/// optionally occur in a capture expression.
-struct CaptureListEntry {
-  VarDecl *Var;
-  PatternBindingDecl *Init;
-
-  CaptureListEntry(VarDecl *Var, PatternBindingDecl *Init)
-  : Var(Var), Init(Init) {
-  }
-};
-
-/// CaptureListExpr - This expression represents the capture list on an explicit
-/// closure.  Because the capture list is evaluated outside of the closure, this
-/// CaptureList wraps the ClosureExpr.  The dynamic semantics are that evaluates
-/// the variable bindings from the capture list, then evaluates the
-/// subexpression (the closure itself) and returns the result.
-class CaptureListExpr : public Expr {
-  ArrayRef<CaptureListEntry> captureList;
-  Expr *closureBody;
-public:
-  CaptureListExpr(ArrayRef<CaptureListEntry> captureList, Expr *closureBody)
-    : Expr(ExprKind::CaptureList, /*Implicit=*/false, Type()),
-      captureList(captureList), closureBody(closureBody) {
-  }
-
-  ArrayRef<CaptureListEntry> getCaptureList() { return captureList; }
-  Expr *getClosureBody() { return closureBody; }
-  const Expr *getClosureBody() const { return closureBody; }
-
-  void setClosureBody(Expr *body) { closureBody = body; }
-
-  /// This is a bit weird, but the capture list is lexically contained within
-  /// the closure, so the ClosureExpr has the full source range.
-  SWIFT_FORWARD_SOURCE_LOCS_TO(closureBody)
-
-  // Implement isa/cast/dyncast/etc.
-  static bool classof(const Expr *E) {
-    return E->getKind() == ExprKind::CaptureList;
-  }
-};
-
-
 /// \brief A base class for closure expressions.
 class AbstractClosureExpr : public Expr, public DeclContext {
   CaptureInfo Captures;
@@ -3607,6 +3565,48 @@ class AutoClosureExpr : public AbstractClosureExpr {
   }
 };
 
+/// Instances of this structure represent elements of the capture list that can
+/// optionally occur in a capture expression.
+struct CaptureListEntry {
+  VarDecl *Var;
+  PatternBindingDecl *Init;
+
+  CaptureListEntry(VarDecl *Var, PatternBindingDecl *Init)
+  : Var(Var), Init(Init) {
+  }
+};
+
+/// CaptureListExpr - This expression represents the capture list on an explicit
+/// closure.  Because the capture list is evaluated outside of the closure, this
+/// CaptureList wraps the ClosureExpr.  The dynamic semantics are that evaluates
+/// the variable bindings from the capture list, then evaluates the
+/// subexpression (the closure itself) and returns the result.
+class CaptureListExpr : public Expr {
+  ArrayRef<CaptureListEntry> captureList;
+  ClosureExpr *closureBody;
+public:
+  CaptureListExpr(ArrayRef<CaptureListEntry> captureList,
+                  ClosureExpr *closureBody)
+    : Expr(ExprKind::CaptureList, /*Implicit=*/false, Type()),
+      captureList(captureList), closureBody(closureBody) {
+  }
+
+  ArrayRef<CaptureListEntry> getCaptureList() { return captureList; }
+  ClosureExpr *getClosureBody() { return closureBody; }
+  const ClosureExpr *getClosureBody() const { return closureBody; }
+
+  void setClosureBody(ClosureExpr *body) { closureBody = body; }
+
+  /// This is a bit weird, but the capture list is lexically contained within
+  /// the closure, so the ClosureExpr has the full source range.
+  SWIFT_FORWARD_SOURCE_LOCS_TO(closureBody)
+
+  // Implement isa/cast/dyncast/etc.
+  static bool classof(const Expr *E) {
+    return E->getKind() == ExprKind::CaptureList;
+  }
+};
+
 /// DynamicTypeExpr - "type(of: base)" - Produces a metatype value.
 ///
 /// The metatype value comes from evaluating an expression then retrieving the

lib/AST/ASTWalker.cpp

@@ -660,8 +660,8 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
         return nullptr;
     }
 
-    Expr *body = expr->getClosureBody();
-    if ((body = doIt(body)))
+    ClosureExpr *body = expr->getClosureBody();
+    if ((body = cast_or_null<ClosureExpr>(doIt(body))))
       expr->setClosureBody(body);
     else
       return nullptr;