Merge pull request swiftlang#70741 from jckarter/pattern-ownership-properties

Add methods to determine the ownership behavior of patterns.

Author: jckarter

include/swift/AST/Ownership.h

@@ -118,14 +118,22 @@ optionalityOf(ReferenceOwnership ownership) {
 }
 
 /// Different kinds of value ownership supported by Swift.
+///
+/// The order of these constants is significant. Ascending order indicates
+/// stricter requirements on the value to be used with the given ownership
+/// kind: any value can be accessed with a shared borrow (so long as there
+/// are no exclusive accesses overlapping). An exclusive `inout` borrow is
+/// only possible for mutable values which the caller already has exclusive
+/// access to or ownership of. Consumption of an owned value requires sole
+/// ownership of that value.
 enum class ValueOwnership : uint8_t {
   /// the context-dependent default ownership (sometimes shared,
   /// sometimes owned)
   Default,
-  /// an 'inout' exclusive, mutating borrow
-  InOut,
   /// a 'borrowing' nonexclusive, usually nonmutating borrow
   Shared,
+  /// an 'inout' exclusive, mutating borrow
+  InOut,
   /// a 'consuming' ownership transfer
   Owned,
 

include/swift/AST/Pattern.h

@@ -230,6 +230,16 @@ class alignas(8) Pattern : public ASTAllocated<Pattern> {
 
   /// Does this pattern have any mutable 'var' bindings?
   bool hasAnyMutableBindings() const;
+  
+  /// Get the ownership behavior of this pattern on the value being matched
+  /// against it.
+  ///
+  /// The pattern must be type-checked for this operation to be valid. If
+  /// \c mostRestrictiveSubpatterns is non-null, the pointed-to vector will be
+  /// populated with references to the subpatterns that cause the pattern to
+  /// have stricter than "shared" ownership behavior for diagnostic purposes.
+  ValueOwnership getOwnership(
+    SmallVectorImpl<Pattern*> *mostRestrictiveSubpatterns = nullptr) const;
 
   static bool classof(const Pattern *P) { return true; }
 
@@ -685,8 +695,10 @@ class ExprPattern : public Pattern {
   DeclContext *DC;
 
   /// A synthesized call to the '~=' operator comparing the match expression
-  /// on the left to the matched value on the right.
-  mutable Expr *MatchExpr = nullptr;
+  /// on the left to the matched value on the right, pairend with a record of the
+  /// ownership of the subject operand.
+  mutable llvm::PointerIntPair<Expr *, 2, ValueOwnership>
+    MatchExprAndOperandOwnership{nullptr, ValueOwnership::Default};
 
   /// An implicit variable used to represent the RHS value of the synthesized
   /// match expression.
@@ -698,6 +710,8 @@ class ExprPattern : public Pattern {
 
   friend class ExprPatternMatchRequest;
 
+  void updateMatchExpr(Expr *matchExpr) const;
+
 public:
   /// Create a new parsed unresolved ExprPattern.
   static ExprPattern *createParsed(ASTContext &ctx, Expr *E, DeclContext *DC);
@@ -711,7 +725,6 @@ class ExprPattern : public Pattern {
 
   Expr *getSubExpr() const { return SubExprAndIsResolved.getPointer(); }
   void setSubExpr(Expr *e) { SubExprAndIsResolved.setPointer(e); }
-
   DeclContext *getDeclContext() const { return DC; }
 
   void setDeclContext(DeclContext *newDC) {
@@ -722,7 +735,17 @@ class ExprPattern : public Pattern {
 
   /// The match expression if it has been computed, \c nullptr otherwise.
   /// Should only be used by the ASTDumper and ASTWalker.
-  Expr *getCachedMatchExpr() const { return MatchExpr; }
+  Expr *getCachedMatchExpr() const {
+    return MatchExprAndOperandOwnership.getPointer();
+  }
+
+  /// Return the ownership of the subject parameter for the `~=` operator being
+  /// used (and thereby, the ownership of the pattern match itself), or
+  /// \c Default if the ownership of the parameter is unresolved.
+  ValueOwnership getCachedMatchOperandOwnership() const {
+    auto ownership = MatchExprAndOperandOwnership.getInt();
+    return ownership;
+  }
 
   /// The match variable if it has been computed, \c nullptr otherwise.
   /// Should only be used by the ASTDumper and ASTWalker.
@@ -731,14 +754,18 @@ class ExprPattern : public Pattern {
   /// A synthesized call to the '~=' operator comparing the match expression
   /// on the left to the matched value on the right.
   Expr *getMatchExpr() const;
+  ValueOwnership getMatchOperandOwnership() const {
+    (void)getMatchExpr();
+    return getCachedMatchOperandOwnership();
+  }
 
   /// An implicit variable used to represent the RHS value of the synthesized
   /// match expression.
   VarDecl *getMatchVar() const;
 
   void setMatchExpr(Expr *e) {
-    assert(MatchExpr && "Should only update an existing MatchExpr");
-    MatchExpr = e;
+    assert(getCachedMatchExpr() && "Should only update an existing MatchExpr");
+    updateMatchExpr(e);
   }
 
   SourceLoc getLoc() const;

lib/AST/ASTDumper.cpp

@@ -928,7 +928,7 @@ namespace {
     using PrintBase::PrintBase;
 
     void printCommon(Pattern *P, const char *Name, StringRef Label) {
-     printHead(Name, PatternColor, Label);
+      printHead(Name, PatternColor, Label);
 
       printFlag(P->isImplicit(), "implicit", ExprModifierColor);
 
@@ -990,6 +990,22 @@ namespace {
     }
     void visitExprPattern(ExprPattern *P, StringRef label) {
       printCommon(P, "pattern_expr", label);
+      switch (P->getCachedMatchOperandOwnership()) {
+      case ValueOwnership::Default:
+        break;
+      case ValueOwnership::Shared:
+        printFieldRaw([](llvm::raw_ostream &os) { os << "borrowing"; },
+                      "ownership");
+        break;
+      case ValueOwnership::InOut:
+        printFieldRaw([](llvm::raw_ostream &os) { os << "mutating"; },
+                      "ownership");
+        break;
+      case ValueOwnership::Owned:
+        printFieldRaw([](llvm::raw_ostream &os) { os << "consuming"; },
+                      "ownership");
+        break;
+      }
       if (auto m = P->getCachedMatchExpr())
         printRec(m);
       else
@@ -2011,6 +2027,22 @@ class PrintStmt : public StmtVisitor<PrintStmt, void, StringRef>,
         printFlag(LabelItem.isDefault(), "default");
 
         if (auto *CasePattern = LabelItem.getPattern()) {
+          switch (CasePattern->getOwnership()) {
+          case ValueOwnership::Default:
+            break;
+          case ValueOwnership::Shared:
+            printFieldRaw([](llvm::raw_ostream &os) { os << "borrowing"; },
+                          "ownership");
+            break;
+          case ValueOwnership::InOut:
+            printFieldRaw([](llvm::raw_ostream &os) { os << "mutating"; },
+                          "ownership");
+            break;
+          case ValueOwnership::Owned:
+            printFieldRaw([](llvm::raw_ostream &os) { os << "consuming"; },
+                          "ownership");
+            break;
+          }
           printRec(CasePattern);
         }
         if (auto *Guard = LabelItem.getGuardExpr()) {

lib/AST/Pattern.cpp

@@ -16,6 +16,7 @@
 
 #include "swift/AST/Pattern.h"
 #include "swift/AST/ASTContext.h"
+#include "swift/AST/ASTVisitor.h"
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/Expr.h"
 #include "swift/AST/GenericEnvironment.h"
@@ -569,6 +570,49 @@ VarDecl *ExprPattern::getMatchVar() const {
       .getMatchVar();
 }
 
+void ExprPattern::updateMatchExpr(Expr *e) const {
+  class FindMatchOperatorDeclRef: public ASTWalker {
+  public:
+    ValueOwnership Ownership = ValueOwnership::Default;
+  
+    PreWalkResult<Expr *> walkToExprPre(Expr *E) override {
+      // See if this is the reference to the ~= operator used.
+      auto declRef = dyn_cast<DeclRefExpr>(E);
+      if (!declRef) {
+        return Action::Continue(E);
+      }
+      auto decl = declRef->getDecl();
+      auto declName = decl->getName();
+      if (!declName.isOperator()) {
+        return Action::Continue(E);
+      }
+      
+      if (!declName.getBaseIdentifier().is("~=")) {
+        return Action::Continue(E);
+      }
+      
+      // We found a `~=` declref. Get the value ownership from the parameter.
+      auto fnTy = decl->getInterfaceType()->castTo<AnyFunctionType>();
+      if (decl->isStatic()) {
+        fnTy = fnTy->getResult()->castTo<AnyFunctionType>();
+      }
+      // Subject value is the right-hand operand to the operator.
+      assert(fnTy->getParams().size() == 2);
+      Ownership = fnTy->getParams()[1].getValueOwnership();
+      // Operators are always normal functions or methods, so their default
+      // parameter ownership is always borrowing.
+      if (Ownership == ValueOwnership::Default) {
+        Ownership = ValueOwnership::Shared;
+      }
+      return Action::Stop();
+    }
+  };
+  FindMatchOperatorDeclRef walker;
+  e->walk(walker);
+
+  MatchExprAndOperandOwnership = {e, walker.Ownership};
+}
+  
 SourceLoc EnumElementPattern::getStartLoc() const {
   return (ParentType && !ParentType->isImplicit())
              ? ParentType->getSourceRange().Start
@@ -680,3 +724,89 @@ void swift::simple_display(llvm::raw_ostream &out, const Pattern *pattern) {
 SourceLoc swift::extractNearestSourceLoc(const Pattern *pattern) {
   return pattern->getLoc();
 }
+
+ValueOwnership
+Pattern::getOwnership(
+  SmallVectorImpl<Pattern *> *mostRestrictiveSubpatterns) const
+{
+  class GetPatternOwnership: public PatternVisitor<GetPatternOwnership, void> {
+  public:
+    ValueOwnership Ownership = ValueOwnership::Shared;
+    SmallVectorImpl<Pattern *> *RestrictingPatterns = nullptr;
+
+    void increaseOwnership(ValueOwnership newOwnership, Pattern *p) {
+      // If the new ownership is stricter than the current ownership, then
+      // clear the restricting patterns we'd collected and start over with the
+      // new stricter ownership.
+      if (newOwnership > Ownership) {
+        Ownership = newOwnership;
+        if (RestrictingPatterns) {
+          RestrictingPatterns->clear();
+        }
+      }
+      
+      if (RestrictingPatterns
+          && newOwnership == Ownership
+          && Ownership > ValueOwnership::Shared) {
+        RestrictingPatterns->push_back(p);
+      }
+    }
+
+#define USE_SUBPATTERN(Kind) \
+    void visit##Kind##Pattern(Kind##Pattern *pattern) { \
+      return visit(pattern->getSubPattern());            \
+    }
+
+    USE_SUBPATTERN(Paren)
+    USE_SUBPATTERN(Typed)
+    USE_SUBPATTERN(Binding)
+#undef USE_SUBPATTERN
+    void visitTuplePattern(TuplePattern *p) {
+      for (auto &element : p->getElements()) {
+        visit(element.getPattern());
+      }
+    }
+    
+    void visitNamedPattern(NamedPattern *p) {
+      // `var` and `let` bindings consume the matched value.
+      // TODO: borrowing/mutating/consuming parameters
+      increaseOwnership(ValueOwnership::Owned, p);
+    }
+    
+    void visitAnyPattern(AnyPattern *p) {
+      /* no change */
+    }
+    void visitBoolPattern(BoolPattern *p) {
+      /* no change */
+    }
+    
+    void visitIsPattern(IsPattern *p) {
+      // Casting currently always consumes.
+      // TODO: Sometimes maybe it doesn't need to be.
+      increaseOwnership(ValueOwnership::Owned, p);
+    }
+    
+    void visitEnumElementPattern(EnumElementPattern *p) {
+      if (p->hasSubPattern()) {
+        visit(p->getSubPattern());
+      }
+    }
+    
+    void visitOptionalSomePattern(OptionalSomePattern *p) {
+      visit(p->getSubPattern());
+    }
+    
+    void visitExprPattern(ExprPattern *p) {
+      // We can't get the ownership reliably if the pattern hasn't been resolved.
+      if (!p->isResolved()) {
+        return;
+      }
+      increaseOwnership(p->getMatchOperandOwnership(), p);
+    }
+  };
+  
+  GetPatternOwnership visitor;
+  visitor.RestrictingPatterns = mostRestrictiveSubpatterns;
+  visitor.visit(const_cast<Pattern *>(this));
+  return visitor.Ownership;
+}

lib/AST/TypeCheckRequests.cpp

@@ -1029,13 +1029,13 @@ ExprPatternMatchRequest::getCachedResult() const {
   if (!EP->MatchVar)
     return llvm::None;
 
-  return ExprPatternMatchResult(EP->MatchVar, EP->MatchExpr);
+  return ExprPatternMatchResult(EP->MatchVar, EP->getCachedMatchExpr());
 }
 
 void ExprPatternMatchRequest::cacheResult(ExprPatternMatchResult result) const {
   auto *EP = std::get<0>(getStorage());
   EP->MatchVar = result.getMatchVar();
-  EP->MatchExpr = result.getMatchExpr();
+  EP->MatchExprAndOperandOwnership.setPointer(result.getMatchExpr());
 }
 
 //----------------------------------------------------------------------------//

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 831; // mark_dependence [nonescaping]
+const uint16_t SWIFTMODULE_VERSION_MINOR = 832; // reorder ValueOwnership
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///

test/Sema/switch-ownership.swift

@@ -0,0 +1,58 @@
+// RUN: %target-swift-frontend -typecheck -dump-ast %s | %FileCheck %s
+
+struct A {
+    static func ~=(pattern: B, subject: A) -> Bool { return true }
+    static func ~=(pattern: C, subject: borrowing A) -> Bool { return true }
+    static func ~=(pattern: D, subject: consuming A) -> Bool { return true }
+}
+struct B { }
+struct C { }
+struct D { }
+struct E { }
+struct F { }
+struct G { }
+
+func ~=(pattern: E, subject: A) -> Bool { return true }
+func ~=(pattern: F, subject: borrowing A) -> Bool { return true }
+func ~=(pattern: G, subject: consuming A) -> Bool { return true }
+
+// CHECK-LABEL: (func_decl{{.*}} "test(value:)"
+func test(value: A) {
+    // CHECK: (switch_stmt
+    switch value {
+    // CHECK: (case_stmt
+    // CHECK:   (case_label_item ownership=borrowing
+    // CHECK:     (pattern_expr type="A" ownership=borrowing
+    case B():
+        break
+    // CHECK: (case_stmt
+    // CHECK:   (case_label_item ownership=borrowing
+    // CHECK:     (pattern_expr type="A" ownership=borrowing
+    case C():
+        break
+    // CHECK: (case_stmt
+    // CHECK:   (case_label_item ownership=consuming
+    // CHECK:     (pattern_expr type="A" ownership=consuming
+    case D():
+        break
+    // CHECK: (case_stmt
+    // CHECK:   (case_label_item ownership=borrowing
+    // CHECK:     (pattern_expr type="A" ownership=borrowing
+    case E():
+        break
+    // CHECK: (case_stmt
+    // CHECK:   (case_label_item ownership=borrowing
+    // CHECK:     (pattern_expr type="A" ownership=borrowing
+    case F():
+        break
+    // CHECK: (case_stmt
+    // CHECK:   (case_label_item ownership=consuming
+    // CHECK:     (pattern_expr type="A" ownership=consuming
+    case G():
+        break
+    // CHECK: (case_stmt
+    // CHECK:   (case_label_item default ownership=borrowing
+    default:
+        break
+    }
+}