A few pattern cleanups + fixes

include/swift/AST/Stmt.h

@@ -84,8 +84,9 @@ class alignas(8) Stmt : public ASTAllocated<Stmt> {
     NumElements : 32
   );
 
-  SWIFT_INLINE_BITFIELD_FULL(CaseStmt, Stmt, 32,
+  SWIFT_INLINE_BITFIELD_FULL(CaseStmt, Stmt, 16+32,
     : NumPadBits,
+    NumCaseBodyVars : 16,
     NumPatterns : 32
   );
 
@@ -1210,8 +1211,8 @@ enum CaseParentKind { Switch, DoCatch };
 ///
 class CaseStmt final
     : public Stmt,
-      private llvm::TrailingObjects<CaseStmt, FallthroughStmt *,
-                                    CaseLabelItem> {
+      private llvm::TrailingObjects<CaseStmt, FallthroughStmt *, CaseLabelItem,
+                                    VarDecl *> {
   friend TrailingObjects;
 
   Stmt *ParentStmt = nullptr;
@@ -1222,15 +1223,17 @@ class CaseStmt final
 
   llvm::PointerIntPair<BraceStmt *, 1, bool> BodyAndHasFallthrough;
 
-  std::optional<MutableArrayRef<VarDecl *>> CaseBodyVariables;
-
   CaseStmt(CaseParentKind ParentKind, SourceLoc ItemIntroducerLoc,
            ArrayRef<CaseLabelItem> CaseLabelItems, SourceLoc UnknownAttrLoc,
            SourceLoc ItemTerminatorLoc, BraceStmt *Body,
-           std::optional<MutableArrayRef<VarDecl *>> CaseBodyVariables,
-           std::optional<bool> Implicit,
+           ArrayRef<VarDecl *> CaseBodyVariables, std::optional<bool> Implicit,
            NullablePtr<FallthroughStmt> fallthroughStmt);
 
+  MutableArrayRef<VarDecl *> getCaseBodyVariablesBuffer() {
+    return {getTrailingObjects<VarDecl *>(),
+            static_cast<size_t>(Bits.CaseStmt.NumCaseBodyVars)};
+  }
+
 public:
   /// Create a parsed 'case'/'default' for 'switch' statement.
   static CaseStmt *
@@ -1244,13 +1247,17 @@ 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,
-         std::optional<MutableArrayRef<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; }
 
@@ -1293,7 +1300,7 @@ class CaseStmt final
   void setBody(BraceStmt *body) { BodyAndHasFallthrough.setPointer(body); }
 
   /// True if the case block declares any patterns with local variable bindings.
-  bool hasBoundDecls() const { return CaseBodyVariables.has_value(); }
+  bool hasCaseBodyVariables() const { return !getCaseBodyVariables().empty(); }
 
   /// Get the source location of the 'case', 'default', or 'catch' of the first
   /// label.
@@ -1345,38 +1352,8 @@ class CaseStmt final
   }
 
   /// Return an ArrayRef containing the case body variables of this CaseStmt.
-  ///
-  /// Asserts if case body variables was not explicitly initialized. In contexts
-  /// where one wants a non-asserting version, \see
-  /// getCaseBodyVariablesOrEmptyArray.
   ArrayRef<VarDecl *> getCaseBodyVariables() const {
-    ArrayRef<VarDecl *> a = *CaseBodyVariables;
-    return a;
-  }
-
-  bool hasCaseBodyVariables() const { return CaseBodyVariables.has_value(); }
-
-  /// Return an MutableArrayRef containing the case body variables of this
-  /// CaseStmt.
-  ///
-  /// Asserts if case body variables was not explicitly initialized. In contexts
-  /// where one wants a non-asserting version, \see
-  /// getCaseBodyVariablesOrEmptyArray.
-  MutableArrayRef<VarDecl *> getCaseBodyVariables() {
-    return *CaseBodyVariables;
-  }
-
-  ArrayRef<VarDecl *> getCaseBodyVariablesOrEmptyArray() const {
-    if (!CaseBodyVariables)
-      return ArrayRef<VarDecl *>();
-    ArrayRef<VarDecl *> a = *CaseBodyVariables;
-    return a;
-  }
-
-  MutableArrayRef<VarDecl *> getCaseBodyVariablesOrEmptyArray() {
-    if (!CaseBodyVariables)
-      return MutableArrayRef<VarDecl *>();
-    return *CaseBodyVariables;
+    return const_cast<CaseStmt *>(this)->getCaseBodyVariablesBuffer();
   }
 
   /// Find the next case statement within the same 'switch' or 'do-catch',

lib/AST/ASTScopeLookup.cpp

@@ -378,10 +378,10 @@ bool CaseLabelItemScope::lookupLocalsOrMembers(DeclConsumer consumer) const {
 }
 
 bool CaseStmtBodyScope::lookupLocalsOrMembers(DeclConsumer consumer) const {
-  for (auto *var : stmt->getCaseBodyVariablesOrEmptyArray())
+  for (auto *var : stmt->getCaseBodyVariables()) {
     if (consumer.consume({var}))
-        return true;
-
+      return true;
+  }
   return false;
 }
 

lib/AST/ASTVerifier.cpp

@@ -2795,7 +2795,7 @@ class Verifier : public ASTWalker {
         // guarantee that all case label items bind corresponding patterns and
         // the case body var decls of a case stmt are created from the var decls
         // of the first case label items.
-        if (!caseStmt->hasBoundDecls()) {
+        if (!caseStmt->hasCaseBodyVariables()) {
           Out << "parent CaseStmt of VarDecl does not have any case body "
                  "decls?!\n";
           abort();

lib/AST/Decl.cpp

@@ -8159,50 +8159,6 @@ SourceRange AbstractStorageDecl::getTypeSourceRangeForDiagnostics() const {
   return SourceRange();
 }
 
-static std::optional<std::pair<CaseStmt *, Pattern *>>
-findParentPatternCaseStmtAndPattern(const VarDecl *inputVD) {
-  auto getMatchingPattern = [&](CaseStmt *cs) -> Pattern * {
-    // Check if inputVD is in our case body var decls if we have any. If we do,
-    // treat its pattern as our first case label item pattern.
-    for (auto *vd : cs->getCaseBodyVariablesOrEmptyArray()) {
-      if (vd == inputVD) {
-        return cs->getMutableCaseLabelItems().front().getPattern();
-      }
-    }
-
-    // Then check the rest of our case label items.
-    for (auto &item : cs->getMutableCaseLabelItems()) {
-      if (item.getPattern()->containsVarDecl(inputVD)) {
-        return item.getPattern();
-      }
-    }
-
-    // Otherwise return false if we do not find anything.
-    return nullptr;
-  };
-
-  // First find our canonical var decl. This is the VarDecl corresponding to the
-  // first case label item of the first case block in the fallthrough chain that
-  // our case block is within. Grab the case stmt associated with that var decl
-  // and start traveling down the fallthrough chain looking for the case
-  // statement that the input VD belongs to by using getMatchingPattern().
-  auto *canonicalVD = inputVD->getCanonicalVarDecl();
-  auto *caseStmt =
-      dyn_cast_or_null<CaseStmt>(canonicalVD->getParentPatternStmt());
-  if (!caseStmt)
-    return std::nullopt;
-
-  if (auto *p = getMatchingPattern(caseStmt))
-    return std::make_pair(caseStmt, p);
-
-  while ((caseStmt = caseStmt->getFallthroughDest().getPtrOrNull())) {
-    if (auto *p = getMatchingPattern(caseStmt))
-      return std::make_pair(caseStmt, p);
-  }
-
-  return std::nullopt;
-}
-
 VarDecl *VarDecl::getCanonicalVarDecl() const {
   // Any var decl without a parent var decl is canonical. This means that before
   // type checking, all var decls are canonical.
@@ -8227,16 +8183,7 @@ VarDecl *VarDecl::getCanonicalVarDecl() const {
 }
 
 Stmt *VarDecl::getRecursiveParentPatternStmt() const {
-  // If our parent is already a pattern stmt, just return that.
-  if (auto *stmt = getParentPatternStmt())
-    return stmt;
-
-  // Otherwise, see if we have a parent var decl. If we do not, then return
-  // nullptr. Otherwise, return the case stmt that we found.
-  auto result = findParentPatternCaseStmtAndPattern(this);
-  if (!result.has_value())
-    return nullptr;
-  return result->first;
+  return getCanonicalVarDecl()->getParentPatternStmt();
 }
 
 /// Return the Pattern involved in initializing this VarDecl.  Recall that the
@@ -8256,17 +8203,34 @@ Pattern *VarDecl::getParentPattern() const {
   }
 
   // If this is a statement parent, dig the pattern out of it.
-  if (auto *stmt = getParentPatternStmt()) {
+  const auto *canonicalVD = getCanonicalVarDecl();
+  if (auto *stmt = canonicalVD->getParentPatternStmt()) {
     if (auto *FES = dyn_cast<ForEachStmt>(stmt))
       return FES->getPattern();
 
     if (auto *cs = dyn_cast<CaseStmt>(stmt)) {
-      // In a case statement, search for the pattern that contains it.  This is
-      // a bit silly, because you can't have something like "case x, y:" anyway.
-      for (auto items : cs->getCaseLabelItems()) {
-        if (items.getPattern()->containsVarDecl(this))
-          return items.getPattern();
+      // In a case statement, search for the pattern that contains it.
+      auto findPattern = [](CaseStmt *cs, const VarDecl *VD) -> Pattern * {
+        for (auto items : cs->getCaseLabelItems()) {
+          if (items.getPattern()->containsVarDecl(VD))
+            return items.getPattern();
+        }
+        return nullptr;
+      };
+      if (auto *P = findPattern(cs, this))
+        return P;
+
+      // If it's not in the CaseStmt, check its fallthrough destination.
+      if (auto fallthrough = cs->getFallthroughDest()) {
+        if (auto *P = findPattern(fallthrough.get(), this))
+          return P;
       }
+
+      // Finally, check the canonical variable, this is necessary to correctly
+      // handle case body vars, we just want to take the first pattern that
+      // declares it in that case.
+      if (auto *P = findPattern(cs, canonicalVD))
+        return P;
     }
 
     if (auto *LCS = dyn_cast<LabeledConditionalStmt>(stmt)) {
@@ -8277,14 +8241,6 @@ Pattern *VarDecl::getParentPattern() const {
     }
   }
 
-  // Otherwise, check if we have to walk our case stmt's var decl list to find
-  // the pattern.
-  if (auto caseStmtPatternPair = findParentPatternCaseStmtAndPattern(this)) {
-    return caseStmtPatternPair->second;
-  }
-
-  // Otherwise, this is a case we do not know or understand. Return nullptr to
-  // signal we do not have any information.
   return nullptr;
 }
 
@@ -8345,7 +8301,7 @@ bool VarDecl::isCaseBodyVariable() const {
   auto *caseStmt = dyn_cast_or_null<CaseStmt>(getRecursiveParentPatternStmt());
   if (!caseStmt)
     return false;
-  return llvm::any_of(caseStmt->getCaseBodyVariablesOrEmptyArray(),
+  return llvm::any_of(caseStmt->getCaseBodyVariables(),
                       [&](VarDecl *vd) { return vd == this; });
 }
 

lib/AST/Pattern.cpp

@@ -208,10 +208,14 @@ namespace {
       return Action::Continue(P);
     }
 
-    // Only walk into an expression insofar as it doesn't open a new scope -
-    // that is, don't walk into a closure body.
     PreWalkResult<Expr *> walkToExprPre(Expr *E) override {
-      if (isa<ClosureExpr>(E)) {
+      // Only walk into an expression insofar as it doesn't open a new scope -
+      // that is, don't walk into a closure body, TapExpr, or
+      // SingleValueStmtExpr. Also don't walk into key paths since any nested
+      // VarDecls are invalid there, and after being diagnosed by key path
+      // resolution the ASTWalker won't visit them.
+      if (isa<ClosureExpr>(E) || isa<TapExpr>(E) ||
+          isa<SingleValueStmtExpr>(E) || isa<KeyPathExpr>(E)) {
         return Action::SkipNode(E);
       }
       return Action::Continue(E);