[AST] Introduce CaseStmt::createImplicit

hamishknight · hamishknight · commit c02c69a7832a · 2025-09-09T13:48:40.000+01:00
This allows us to re-use the same logic to create the case body
variables.
diff --git a/include/swift/AST/Stmt.h b/include/swift/AST/Stmt.h
@@ -1243,13 +1243,17 @@ class CaseStmt final
                                        ArrayRef<CaseLabelItem> CaseLabelItems,
                                        BraceStmt *Body);
 
+  static CaseStmt *
+  createImplicit(ASTContext &ctx, CaseParentKind parentKind,
+                 ArrayRef<CaseLabelItem> caseLabelItems, BraceStmt *body,
+                 NullablePtr<FallthroughStmt> fallthroughStmt = nullptr);
+
   static CaseStmt *
   create(ASTContext &C, CaseParentKind ParentKind, SourceLoc ItemIntroducerLoc,
          ArrayRef<CaseLabelItem> CaseLabelItems, SourceLoc UnknownAttrLoc,
          SourceLoc ItemTerminatorLoc, BraceStmt *Body,
-         ArrayRef<VarDecl *> CaseBodyVariables,
-         std::optional<bool> Implicit = std::nullopt,
-         NullablePtr<FallthroughStmt> fallthroughStmt = nullptr);
+         ArrayRef<VarDecl *> CaseBodyVariables, std::optional<bool> Implicit,
+         NullablePtr<FallthroughStmt> fallthroughStmt);
 
   CaseParentKind getParentKind() const { return ParentKind; }
 
diff --git a/lib/AST/Stmt.cpp b/lib/AST/Stmt.cpp
@@ -897,11 +897,23 @@ CaseStmt *CaseStmt::createParsedDoCatch(ASTContext &ctx, SourceLoc catchLoc,
 }
 
 CaseStmt *
-CaseStmt::create(ASTContext &ctx, CaseParentKind ParentKind, SourceLoc caseLoc,
-                 ArrayRef<CaseLabelItem> caseLabelItems,
-                 SourceLoc unknownAttrLoc, SourceLoc colonLoc, BraceStmt *body,
-                 ArrayRef<VarDecl *> caseVarDecls, std::optional<bool> implicit,
-                 NullablePtr<FallthroughStmt> fallthroughStmt) {
+CaseStmt::createImplicit(ASTContext &ctx, CaseParentKind parentKind,
+                         ArrayRef<CaseLabelItem> caseLabelItems,
+                         BraceStmt *body,
+                         NullablePtr<FallthroughStmt> fallthroughStmt) {
+  auto caseVarDecls = getCaseVarDecls(ctx, caseLabelItems);
+  return create(ctx, parentKind, /*catchLoc*/ SourceLoc(), caseLabelItems,
+                /*unknownAttrLoc*/ SourceLoc(), /*colonLoc*/ SourceLoc(), body,
+                caseVarDecls, /*implicit*/ true, fallthroughStmt);
+}
+
+CaseStmt *CaseStmt::create(ASTContext &ctx, CaseParentKind ParentKind,
+                           SourceLoc caseLoc,
+                           ArrayRef<CaseLabelItem> caseLabelItems,
+                           SourceLoc unknownAttrLoc, SourceLoc colonLoc,
+                           BraceStmt *body, ArrayRef<VarDecl *> caseVarDecls,
+                           std::optional<bool> implicit,
+                           NullablePtr<FallthroughStmt> fallthroughStmt) {
   void *mem =
       ctx.Allocate(totalSizeToAlloc<FallthroughStmt *, CaseLabelItem>(
                        fallthroughStmt.isNonNull(), caseLabelItems.size()),
diff --git a/lib/Sema/DerivedConformance/DerivedConformance.cpp b/lib/Sema/DerivedConformance/DerivedConformance.cpp
@@ -805,9 +805,8 @@ DeclRefExpr *DerivedConformance::convertEnumToIndex(SmallVectorImpl<ASTNode> &st
     assignExpr->setType(TupleType::getEmpty(C));
     auto body = BraceStmt::create(C, SourceLoc(), ASTNode(assignExpr),
                                   SourceLoc());
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     labelItem, SourceLoc(), SourceLoc(), body,
-                                     /*case body vardecls*/ std::nullopt));
+    cases.push_back(
+        CaseStmt::createImplicit(C, CaseParentKind::Switch, labelItem, body));
   }
 
   // generate: switch enumVar { }
@@ -967,9 +966,7 @@ CaseStmt *DerivedConformance::unavailableEnumElementCaseStmt(
   auto *callExpr =
       DerivedConformance::createDiagnoseUnavailableCodeReachedCallExpr(C);
   auto body = BraceStmt::create(C, SourceLoc(), {callExpr}, SourceLoc());
-  return CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(), labelItem,
-                          SourceLoc(), SourceLoc(), body, {},
-                          /*implicit*/ true);
+  return CaseStmt::createImplicit(C, CaseParentKind::Switch, labelItem, body);
 }
 
 /// Creates a named variable based on a prefix character and a numeric index.
diff --git a/lib/Sema/DerivedConformance/DerivedConformanceCodable.cpp b/lib/Sema/DerivedConformance/DerivedConformanceCodable.cpp
@@ -946,27 +946,10 @@ createEnumSwitch(ASTContext &C, DeclContext *DC, Expr *expr, EnumDecl *enumDecl,
     // .<elt>(let a0, let a1, ...)
     SmallVector<VarDecl *, 3> payloadVars;
     Pattern *subpattern = nullptr;
-    ArrayRef<VarDecl *> caseBodyVarDecls;
 
     if (createSubpattern) {
       subpattern = DerivedConformance::enumElementPayloadSubpattern(
           elt, 'a', DC, payloadVars, /* useLabels */ true);
-
-      auto hasBoundDecls = !payloadVars.empty();
-      if (hasBoundDecls) {
-        // We allocated a direct copy of our var decls for the case
-        // body.
-        auto copy = C.Allocate<VarDecl *>(payloadVars.size());
-        for (unsigned i : indices(payloadVars)) {
-          auto *vOld = payloadVars[i];
-          auto *vNew = new (C) VarDecl(
-              /*IsStatic*/ false, vOld->getIntroducer(), vOld->getNameLoc(),
-              vOld->getName(), vOld->getDeclContext());
-          vNew->setImplicit();
-          copy[i] = vNew;
-        }
-        caseBodyVarDecls = copy;
-      }
     }
 
     // CodingKeys.x
@@ -985,10 +968,8 @@ createEnumSwitch(ASTContext &C, DeclContext *DC, Expr *expr, EnumDecl *enumDecl,
                                                      subpattern, DC);
 
       auto labelItem = CaseLabelItem(pat);
-      auto stmt =
-          CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(), labelItem,
-                           SourceLoc(), SourceLoc(), caseBody,
-                           caseBodyVarDecls);
+      auto stmt = CaseStmt::createImplicit(C, CaseParentKind::Switch, labelItem,
+                                           caseBody);
       cases.push_back(stmt);
     }
   }
diff --git a/lib/Sema/DerivedConformance/DerivedConformanceCodingKey.cpp b/lib/Sema/DerivedConformance/DerivedConformanceCodingKey.cpp
@@ -222,10 +222,8 @@ deriveBodyCodingKey_enum_stringValue(AbstractFunctionDecl *strValDecl, void *) {
       auto *returnStmt = ReturnStmt::createImplicit(C, caseValue);
       auto *caseBody = BraceStmt::create(C, SourceLoc(), ASTNode(returnStmt),
                                          SourceLoc());
-      cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                       labelItem, SourceLoc(), SourceLoc(),
-                                       caseBody,
-                                       /*case body var decls*/ std::nullopt));
+      cases.push_back(CaseStmt::createImplicit(C, CaseParentKind::Switch,
+                                               labelItem, caseBody));
     }
 
     auto *selfRef = DerivedConformance::createSelfDeclRef(strValDecl);
@@ -292,9 +290,8 @@ deriveBodyCodingKey_init_stringValue(AbstractFunctionDecl *initDecl, void *) {
 
     auto *body = BraceStmt::create(C, SourceLoc(), ASTNode(assignment),
                                    SourceLoc());
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     labelItem, SourceLoc(), SourceLoc(), body,
-                                     /*case body var decls*/ std::nullopt));
+    cases.push_back(
+        CaseStmt::createImplicit(C, CaseParentKind::Switch, labelItem, body));
   }
 
   auto *anyPat = AnyPattern::createImplicit(C);
@@ -303,10 +300,8 @@ deriveBodyCodingKey_init_stringValue(AbstractFunctionDecl *initDecl, void *) {
   auto *dfltReturnStmt = new (C) FailStmt(SourceLoc(), SourceLoc());
   auto *dfltBody = BraceStmt::create(C, SourceLoc(), ASTNode(dfltReturnStmt),
                                      SourceLoc());
-  cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                   dfltLabelItem, SourceLoc(), SourceLoc(),
-                                   dfltBody,
-                                   /*case body var decls*/ std::nullopt));
+  cases.push_back(CaseStmt::createImplicit(C, CaseParentKind::Switch,
+                                           dfltLabelItem, dfltBody));
 
   auto *stringValueDecl = initDecl->getParameters()->get(0);
   auto *stringValueRef = new (C) DeclRefExpr(stringValueDecl, DeclNameLoc(),
diff --git a/lib/Sema/DerivedConformance/DerivedConformanceComparable.cpp b/lib/Sema/DerivedConformance/DerivedConformanceComparable.cpp
@@ -127,23 +127,6 @@ deriveBodyComparable_enum_hasAssociatedValues_lt(AbstractFunctionDecl *ltDecl, v
     auto *rhsElemPat = EnumElementPattern::createImplicit(
         enumType, elt, rhsSubpattern, /*DC*/ ltDecl);
 
-    auto hasBoundDecls = !lhsPayloadVars.empty();
-    ArrayRef<VarDecl *> caseBodyVarDecls;
-    if (hasBoundDecls) {
-      // We allocated a direct copy of our lhs var decls for the case
-      // body.
-      auto copy = C.Allocate<VarDecl *>(lhsPayloadVars.size());
-      for (unsigned i : indices(lhsPayloadVars)) {
-        auto *vOld = lhsPayloadVars[i];
-        auto *vNew = new (C) VarDecl(
-            /*IsStatic*/ false, vOld->getIntroducer(),
-            vOld->getNameLoc(), vOld->getName(), vOld->getDeclContext());
-        vNew->setImplicit();
-        copy[i] = vNew;
-      }
-      caseBodyVarDecls = copy;
-    }
-
     // case (.<elt>(let l0, let l1, ...), .<elt>(let r0, let r1, ...))
     auto caseTuplePattern = TuplePattern::createImplicit(C, {
       TuplePatternElt(lhsElemPat), TuplePatternElt(rhsElemPat) });
@@ -177,9 +160,8 @@ deriveBodyComparable_enum_hasAssociatedValues_lt(AbstractFunctionDecl *ltDecl, v
 
     auto body = BraceStmt::create(C, SourceLoc(), statementsInCase,
                                   SourceLoc());
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     labelItem, SourceLoc(), SourceLoc(), body,
-                                     caseBodyVarDecls));
+    cases.push_back(
+        CaseStmt::createImplicit(C, CaseParentKind::Switch, labelItem, body));
   }
 
   // default: result = <enum index>(lhs) < <enum index>(rhs)
@@ -190,10 +172,8 @@ deriveBodyComparable_enum_hasAssociatedValues_lt(AbstractFunctionDecl *ltDecl, v
     auto defaultPattern = AnyPattern::createImplicit(C);
     auto defaultItem = CaseLabelItem::getDefault(defaultPattern);
     auto body = deriveBodyComparable_enum_noAssociatedValues_lt(ltDecl, nullptr).first;
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     defaultItem, SourceLoc(), SourceLoc(),
-                                     body,
-                                     /*case body var decls*/ std::nullopt));
+    cases.push_back(
+        CaseStmt::createImplicit(C, CaseParentKind::Switch, defaultItem, body));
   }
 
   // switch (a, b) { <case statements> }
diff --git a/lib/Sema/DerivedConformance/DerivedConformanceEquatableHashable.cpp b/lib/Sema/DerivedConformance/DerivedConformanceEquatableHashable.cpp
@@ -193,23 +193,6 @@ deriveBodyEquatable_enum_hasAssociatedValues_eq(AbstractFunctionDecl *eqDecl,
     auto *rhsElemPat = EnumElementPattern::createImplicit(
         enumType, elt, rhsSubpattern, /*DC*/ eqDecl);
 
-    auto hasBoundDecls = !lhsPayloadVars.empty();
-    ArrayRef<VarDecl *> caseBodyVarDecls;
-    if (hasBoundDecls) {
-      // We allocated a direct copy of our lhs var decls for the case
-      // body.
-      auto copy = C.Allocate<VarDecl *>(lhsPayloadVars.size());
-      for (unsigned i : indices(lhsPayloadVars)) {
-        auto *vOld = lhsPayloadVars[i];
-        auto *vNew = new (C) VarDecl(
-            /*IsStatic*/ false, vOld->getIntroducer(),
-            vOld->getNameLoc(), vOld->getName(), vOld->getDeclContext());
-        vNew->setImplicit();
-        copy[i] = vNew;
-      }
-      caseBodyVarDecls = copy;
-    }
-
     // case (.<elt>(let l0, let l1, ...), .<elt>(let r0, let r1, ...))
     auto caseTuplePattern = TuplePattern::createImplicit(C, {
       TuplePatternElt(lhsElemPat), TuplePatternElt(rhsElemPat) });
@@ -244,9 +227,8 @@ deriveBodyEquatable_enum_hasAssociatedValues_eq(AbstractFunctionDecl *eqDecl,
 
     auto body = BraceStmt::create(C, SourceLoc(), statementsInCase,
                                   SourceLoc());
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     labelItem, SourceLoc(), SourceLoc(), body,
-                                     caseBodyVarDecls));
+    cases.push_back(
+        CaseStmt::createImplicit(C, CaseParentKind::Switch, labelItem, body));
   }
 
   // default: result = false
@@ -261,10 +243,8 @@ deriveBodyEquatable_enum_hasAssociatedValues_eq(AbstractFunctionDecl *eqDecl,
     auto *returnStmt = ReturnStmt::createImplicit(C, falseExpr);
     auto body = BraceStmt::create(C, SourceLoc(), ASTNode(returnStmt),
                                   SourceLoc());
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     defaultItem, SourceLoc(), SourceLoc(),
-                                     body,
-                                     /*case body var decls*/ std::nullopt));
+    cases.push_back(
+        CaseStmt::createImplicit(C, CaseParentKind::Switch, defaultItem, body));
   }
 
   // switch (a, b) { <case statements> }
@@ -735,26 +715,9 @@ deriveBodyHashable_enum_hasAssociatedValues_hashInto(
       statements.emplace_back(ASTNode(combineExpr));
     }
 
-    auto hasBoundDecls = !payloadVars.empty();
-    ArrayRef<VarDecl *> caseBodyVarDecls;
-    if (hasBoundDecls) {
-      auto copy = C.Allocate<VarDecl *>(payloadVars.size());
-      for (unsigned i : indices(payloadVars)) {
-        auto *vOld = payloadVars[i];
-        auto *vNew = new (C) VarDecl(
-            /*IsStatic*/ false, vOld->getIntroducer(),
-            vOld->getNameLoc(), vOld->getName(), vOld->getDeclContext());
-        vNew->setImplicit();
-        copy[i] = vNew;
-      }
-      caseBodyVarDecls = copy;
-    }
-
     auto body = BraceStmt::create(C, SourceLoc(), statements, SourceLoc());
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     labelItem, SourceLoc(), SourceLoc(), body,
-                                     caseBodyVarDecls,
-                                     /*implicit*/ true));
+    cases.push_back(
+        CaseStmt::createImplicit(C, CaseParentKind::Switch, labelItem, body));
   }
 
   // generate: switch enumVar { }
diff --git a/lib/Sema/DerivedConformance/DerivedConformanceRawRepresentable.cpp b/lib/Sema/DerivedConformance/DerivedConformanceRawRepresentable.cpp
@@ -129,9 +129,8 @@ deriveBodyRawRepresentable_raw(AbstractFunctionDecl *toRawDecl, void *) {
     auto body = BraceStmt::create(C, SourceLoc(),
                                   ASTNode(returnStmt), SourceLoc());
 
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     labelItem, SourceLoc(), SourceLoc(), body,
-                                     /*case body var decls*/ std::nullopt));
+    cases.push_back(
+        CaseStmt::createImplicit(C, CaseParentKind::Switch, labelItem, body));
   }
 
   auto selfRef = DerivedConformance::createSelfDeclRef(toRawDecl);
@@ -363,10 +362,8 @@ deriveBodyRawRepresentable_init(AbstractFunctionDecl *initDecl, void *) {
                                   stmts, SourceLoc());
 
     // cases.append("case \(litPat): \(body)")
-    cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                     CaseLabelItem(litPat), SourceLoc(),
-                                     SourceLoc(), body,
-                                     /*case body var decls*/ std::nullopt));
+    cases.push_back(CaseStmt::createImplicit(C, CaseParentKind::Switch,
+                                             CaseLabelItem(litPat), body));
     ++Idx;
   }
 
@@ -376,10 +373,8 @@ deriveBodyRawRepresentable_init(AbstractFunctionDecl *initDecl, void *) {
   auto dfltReturnStmt = new (C) FailStmt(SourceLoc(), SourceLoc());
   auto dfltBody = BraceStmt::create(C, SourceLoc(),
                                     ASTNode(dfltReturnStmt), SourceLoc());
-  cases.push_back(CaseStmt::create(C, CaseParentKind::Switch, SourceLoc(),
-                                   dfltLabelItem, SourceLoc(), SourceLoc(),
-                                   dfltBody,
-                                   /*case body var decls*/ std::nullopt));
+  cases.push_back(CaseStmt::createImplicit(C, CaseParentKind::Switch,
+                                           dfltLabelItem, dfltBody));
 
   auto rawDecl = initDecl->getParameters()->get(0);
   auto rawRef = new (C) DeclRefExpr(rawDecl, DeclNameLoc(), /*implicit*/true);
diff --git a/unittests/Sema/ConstraintGenerationTests.cpp b/unittests/Sema/ConstraintGenerationTests.cpp
@@ -286,10 +286,8 @@ TEST_F(SemaTest, TestSwitchExprLocator) {
       {IntegerLiteralExpr::createFromUnsigned(Context, 1, SourceLoc())});
   auto *truePattern = ExprPattern::createImplicit(
       Context, new (Context) BooleanLiteralExpr(true, SourceLoc()), DC);
-  auto *trueCase =
-      CaseStmt::create(Context, CaseParentKind::Switch, SourceLoc(),
-                       {CaseLabelItem(truePattern)}, SourceLoc(), SourceLoc(),
-                       trueBrace, /*caseBodyVars*/ std::nullopt);
+  auto *trueCase = CaseStmt::createImplicit(
+      Context, CaseParentKind::Switch, {CaseLabelItem(truePattern)}, trueBrace);
 
   // case false: 2
   auto *falseBrace = BraceStmt::createImplicit(
@@ -298,9 +296,8 @@ TEST_F(SemaTest, TestSwitchExprLocator) {
   auto *falsePattern = ExprPattern::createImplicit(
       Context, new (Context) BooleanLiteralExpr(false, SourceLoc()), DC);
   auto *falseCase =
-      CaseStmt::create(Context, CaseParentKind::Switch, SourceLoc(),
-                       {CaseLabelItem(falsePattern)}, SourceLoc(), SourceLoc(),
-                       falseBrace, /*caseBodyVars*/ std::nullopt);
+      CaseStmt::createImplicit(Context, CaseParentKind::Switch,
+                               {CaseLabelItem(falsePattern)}, falseBrace);
 
   auto *subject = new (Context) BooleanLiteralExpr(true, SourceLoc());
 
