[Sema/SILGen] Omnibus of init accessor feature improvements

- Diagnose standalone `self` within init accessors
- Diagnose references to members not listed in `initializes` or `accesses` attributes within init accessors
- Enforce that `@out` parameters are fully initialized before every terminator
- Detect and don't synthesize memberwise initializer with intersecting init accessor calls
- Diagnose situations when memberwise init cannot be synthesized due to use of not-yet-initialized properties
- Allow initialization expressions when computed property has init accessor;
- Synthesize default argument for init accessor property included in memberwise initializer.

(cherry picked from commit 5613006)
(cherry picked from commit 935142f)
(cherry picked from commit 3c924be)
(cherry picked from commit db024d9)
(cherry picked from commit f6fd0bc)
(cherry picked from commit ddcfe01)
(cherry picked from commit 4f59538)
(cherry picked from commit cffc3fd)
(cherry picked from commit 6ca9728)
(cherry picked from commit 34c8cf6)
(cherry picked from commit 8b1c9c9)
(cherry picked from commit d1554f2)
(cherry picked from commit fc895b4)
(cherry picked from commit f58d407)

Author: xedin

include/swift/AST/Decl.h

@@ -5319,6 +5319,16 @@ class AbstractStorageDecl : public ValueDecl {
   /// it.
   bool hasStorage() const;
 
+  /// Return true if this is a VarDecl that has init accessor associated
+  /// with it.
+  bool hasInitAccessor() const;
+
+  /// Return true if this is a property that either has storage
+  /// or init accessor associated with it.
+  bool supportsInitialization() const {
+    return hasStorage() || hasInitAccessor();
+  }
+
   /// Return true if this storage has the basic accessors/capability
   /// to be mutated.  This is generally constant after the accessors are
   /// installed by the parser/importer/whatever.

include/swift/AST/DeclContext.h

@@ -82,6 +82,7 @@ namespace swift {
   class SerializedDefaultArgumentInitializer;
   class SerializedTopLevelCodeDecl;
   class StructDecl;
+  class AccessorDecl;
 
 namespace serialization {
 using DeclID = llvm::PointerEmbeddedInt<unsigned, 31>;
@@ -457,6 +458,18 @@ class alignas(1 << DeclContextAlignInBits) DeclContext
     return const_cast<DeclContext*>(this)->getInnermostMethodContext();
   }
 
+  /// Returns the innermost accessor context that belongs to a property.
+  ///
+  /// This routine looks through closure, initializer, and local function
+  /// contexts to find the innermost accessor declaration.
+  ///
+  /// \returns the innermost accessor, or null if there is no such context.
+  LLVM_READONLY
+  AccessorDecl *getInnermostPropertyAccessorContext();
+  const AccessorDecl *getInnermostPropertyAccessorContext() const {
+    return const_cast<DeclContext*>(this)->getInnermostPropertyAccessorContext();
+  }
+
   /// Returns the innermost type context.
   ///
   /// This routine looks through closure, initializer, and local function

include/swift/AST/DiagnosticsSema.def

@@ -7296,7 +7296,22 @@ ERROR(init_accessor_accesses_attribute_on_other_declaration,none,
 ERROR(init_accessor_property_both_init_and_accessed,none,
       "property %0 cannot be both initialized and accessed",
       (DeclName))
-
+ERROR(invalid_use_of_self_in_init_accessor,none,
+      "'self' within init accessors can only be used to reference "
+      "properties listed in 'initializes' and 'accesses'; "
+      "init accessors are run before 'self' is fully available", ())
+ERROR(init_accessor_invalid_member_ref,none,
+      "cannot reference instance member %0; init accessors can only "
+      "refer to instance properties listed in 'initializes' and "
+      "'accesses' attributes",
+      (DeclNameRef))
+ERROR(cannot_synthesize_memberwise_due_to_property_init_order,none,
+      "cannot synthesize memberwise initializer",
+      ())
+NOTE(out_of_order_access_in_init_accessor,none,
+     "init accessor for %0 cannot access stored property %1 because it "
+     "is called before %1 is initialized",
+     (Identifier, Identifier))
 
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

include/swift/AST/TypeCheckRequests.h

@@ -4312,6 +4312,22 @@ class IsNonUserModuleRequest
   bool isCached() const { return true; }
 };
 
+class HasInitAccessorRequest
+    : public SimpleRequest<HasInitAccessorRequest, bool(AbstractStorageDecl *),
+                           RequestFlags::Cached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  // Evaluation.
+  bool evaluate(Evaluator &evaluator, AbstractStorageDecl *decl) const;
+
+public:
+  bool isCached() const { return true; }
+};
+
 class InitAccessorReferencedVariablesRequest
     : public SimpleRequest<InitAccessorReferencedVariablesRequest,
                            ArrayRef<VarDecl *>(DeclAttribute *, AccessorDecl *,

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -487,6 +487,9 @@ SWIFT_REQUEST(TypeChecker, IsNonUserModuleRequest,
 SWIFT_REQUEST(TypeChecker, TypeCheckObjCImplementationRequest,
               unsigned(ExtensionDecl *),
               Cached, NoLocationInfo)
+SWIFT_REQUEST(TypeChecker, HasInitAccessorRequest,
+              bool(AbstractStorageDecl *), Cached,
+              NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, InitAccessorReferencedVariablesRequest,
               ArrayRef<VarDecl *>(DeclAttribute *, AccessorDecl *,
                                   ArrayRef<Identifier>),

include/swift/Sema/CSFix.h

@@ -447,6 +447,10 @@ enum class FixKind : uint8_t {
 
   /// Ignore missing 'each' keyword before value pack reference.
   IgnoreMissingEachKeyword,
+
+  /// Ignore the fact that member couldn't be referenced within init accessor
+  /// because its name doesn't appear in 'initializes' or 'accesses' attributes.
+  AllowInvalidMemberReferenceInInitAccessor,
 };
 
 class ConstraintFix {
@@ -3536,6 +3540,39 @@ class IgnoreMissingEachKeyword final : public ConstraintFix {
   }
 };
 
+class AllowInvalidMemberReferenceInInitAccessor final : public ConstraintFix {
+  DeclNameRef MemberName;
+
+  AllowInvalidMemberReferenceInInitAccessor(ConstraintSystem &cs,
+                                            DeclNameRef memberName,
+                                            ConstraintLocator *locator)
+      : ConstraintFix(cs, FixKind::AllowInvalidMemberReferenceInInitAccessor,
+                      locator),
+        MemberName(memberName) {}
+
+public:
+  std::string getName() const override {
+    llvm::SmallVector<char, 16> scratch;
+    auto memberName = MemberName.getString(scratch);
+    return "allow reference to member '" + memberName.str() +
+           "' in init accessor";
+  }
+
+  bool diagnose(const Solution &solution, bool asNote = false) const override;
+
+  bool diagnoseForAmbiguity(CommonFixesArray commonFixes) const override {
+    return diagnose(*commonFixes.front().first);
+  }
+
+  static AllowInvalidMemberReferenceInInitAccessor *
+  create(ConstraintSystem &cs, DeclNameRef memberName,
+         ConstraintLocator *locator);
+
+  static bool classof(const ConstraintFix *fix) {
+    return fix->getKind() == FixKind::AllowInvalidMemberReferenceInInitAccessor;
+  }
+};
+
 } // end namespace constraints
 } // end namespace swift
 

include/swift/Sema/ConstraintSystem.h

@@ -1879,6 +1879,11 @@ struct MemberLookupResult {
     /// This is a static member being access through a protocol metatype
     /// but its result type doesn't conform to this protocol.
     UR_InvalidStaticMemberOnProtocolMetatype,
+
+    /// This is a member that doesn't appear in 'initializes' and/or
+    /// 'accesses' attributes of the init accessor and therefore canno
+    /// t be referenced in its body.
+    UR_UnavailableWithinInitAccessor,
   };
 
   /// This is a list of considered (but rejected) candidates, along with a

lib/AST/Decl.cpp

@@ -6711,6 +6711,12 @@ Type AbstractStorageDecl::getValueInterfaceType() const {
   return cast<SubscriptDecl>(this)->getElementInterfaceType();
 }
 
+bool AbstractStorageDecl::hasInitAccessor() const {
+  return evaluateOrDefault(
+      getASTContext().evaluator,
+      HasInitAccessorRequest{const_cast<AbstractStorageDecl *>(this)}, false);
+}
+
 VarDecl::VarDecl(DeclKind kind, bool isStatic, VarDecl::Introducer introducer,
                  SourceLoc nameLoc, Identifier name,
                  DeclContext *dc, StorageIsMutable_t supportsMutation)
@@ -7159,6 +7165,12 @@ bool VarDecl::isMemberwiseInitialized(bool preferDeclaredProperties) const {
       isBackingStorageForDeclaredProperty(this))
     return false;
 
+  // If this is a computed property with `init` accessor, it's
+  // memberwise initializable when it could be used to initialize
+  // other stored properties.
+  if (auto *init = getAccessor(AccessorKind::Init))
+    return init->getAttrs().hasAttribute<InitializesAttr>();
+
   // If this is a computed property, it's not memberwise initialized unless
   // the caller has asked for the declared properties and it is either a
   // `lazy` property or a property with an attached wrapper.

lib/AST/DeclContext.cpp

@@ -211,6 +211,24 @@ AbstractFunctionDecl *DeclContext::getInnermostMethodContext() {
   return nullptr;
 }
 
+AccessorDecl *DeclContext::getInnermostPropertyAccessorContext() {
+  auto dc = this;
+  do {
+    if (auto decl = dc->getAsDecl()) {
+      auto accessor = dyn_cast<AccessorDecl>(decl);
+      // If we found a non-accessor decl, we're done.
+      if (accessor == nullptr)
+        return nullptr;
+
+      auto *storage = accessor->getStorage();
+      if (isa<VarDecl>(storage) && storage->getDeclContext()->isTypeContext())
+        return accessor;
+    }
+  } while ((dc = dc->getParent()));
+
+  return nullptr;
+}
+
 bool DeclContext::isTypeContext() const {
   if (auto decl = getAsDecl())
     return isa<NominalTypeDecl>(decl) || isa<ExtensionDecl>(decl);

lib/Parse/ParseExpr.cpp

@@ -1059,14 +1059,14 @@ bool Parser::isStartOfGetSetAccessor() {
   // The only case this can happen is if the accessor label is immediately after
   // a brace (possibly preceded by attributes).  "get" is implicit, so it can't
   // be checked for.  Conveniently however, get/set properties are not allowed
-  // to have initializers, so we don't have an ambiguity, we just have to check
-  // for observing accessors.
+  // to have initializers unless they have `init` accessor, so we don't have an
+  // ambiguity, we just have to check for observing accessors and init accessor.
   //
   // If we have a 'didSet' or a 'willSet' label, disambiguate immediately as
   // an accessor block.
   Token NextToken = peekToken();
   if (NextToken.isContextualKeyword("didSet") ||
-      NextToken.isContextualKeyword("willSet"))
+      NextToken.isContextualKeyword("willSet") || NextToken.is(tok::kw_init))
     return true;
 
   // If we don't have attributes, then it cannot be an accessor block.
@@ -1087,9 +1087,9 @@ bool Parser::isStartOfGetSetAccessor() {
       skipSingle();
   }
 
-  // Check if we have 'didSet'/'willSet' after attributes.
+  // Check if we have 'didSet'/'willSet' or 'init' after attributes.
   return Tok.isContextualKeyword("didSet") ||
-         Tok.isContextualKeyword("willSet");
+         Tok.isContextualKeyword("willSet") || Tok.is(tok::kw_init);
 }
 
 /// Recover invalid uses of trailing closures in a situation