From c27f79e3eb9f245bfe98064ad2582366a9a41750 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Sun, 24 Feb 2019 16:48:50 +0000
Subject: [PATCH 01/18] Make Self available to instance member functions
 (SE-0068?)

---
 lib/Sema/TypeCheckConstraints.cpp | 10 +++++++
 test/decl/func/dynamic_self.swift | 46 +++++++++++++++++++++++++++++--
 2 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/lib/Sema/TypeCheckConstraints.cpp b/lib/Sema/TypeCheckConstraints.cpp
index dd9cdcd38a92c..b6fc8f8f31b7e 100644
--- a/lib/Sema/TypeCheckConstraints.cpp
+++ b/lib/Sema/TypeCheckConstraints.cpp
@@ -551,6 +551,16 @@ resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE, DeclContext *DC) {
     };
 
     if (!isConfused) {
+      if (Name.getBaseName().userFacingName() == "Self") {
+        DeclName selfName(Context.getIdentifier("self"));
+        auto selfInstance = lookupUnqualified(DC, selfName, Loc, lookupOptions);
+        if (!selfInstance.empty()) {
+          ValueDecl *D = selfInstance.front().getValueDecl();
+          Expr *E = new (Context) DeclRefExpr(D, nameLoc, /*Implicit=*/false);
+          return new (Context) DynamicTypeExpr(Loc, Loc, E, Loc, Type());
+        }
+      }
+
       TypoCorrectionResults corrections(*this, Name, nameLoc);
       performTypoCorrection(DC, UDRE->getRefKind(), Type(),
                             lookupOptions, corrections);
diff --git a/test/decl/func/dynamic_self.swift b/test/decl/func/dynamic_self.swift
index 89c380b9de1d0..be2aaa4d477d7 100644
--- a/test/decl/func/dynamic_self.swift
+++ b/test/decl/func/dynamic_self.swift
@@ -89,7 +89,7 @@ class C1 {
 
     if b { return self.init(int: 5) }
 
-    return Self() // expected-error{{use of unresolved identifier 'Self'; did you mean 'self'?}}
+    return Self() // expected-error{{non-nominal type 'Self.Type' does not support explicit initialization}}
   }
 
   // This used to crash because metatype construction went down a
@@ -412,4 +412,46 @@ class SelfOperator {
 func useSelfOperator() {
   let s = SelfOperator()
   _ = s + s
-}
\ No newline at end of file
+}
+
+// These references to Self are now possible
+
+class A<T> {
+  let b: Int
+  required init(a: Int) {
+    print("\(Self).\(#function)")
+    b = a
+  }
+  static func z() {
+    print("\(Self.self).\(#function)")
+  }
+  class func y() {
+    print("\(Self).\(#function)")
+  }
+  func x() {
+    print("\(Self.self).\(#function)")
+    Self.y()
+    Self.z()
+    _ = Self.init(a: 77)
+  }
+}
+
+class B: A<Int> {
+  let a: Int
+  required convenience init(a: Int) {
+    print("\(Self).\(#function)")
+    self.init()
+  }
+  init() {
+    print("\(Self.self).\(#function)")
+    Self.y()
+    Self.z()
+    a = 99
+    super.init(a: 88)
+  }
+  override class func y() {
+    print("\(Self).\(#function)")
+  }
+}
+
+B().x()

From d08b319bd5bc13b5b5165372fa48df4ffd90b9f9 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Tue, 26 Feb 2019 19:32:13 +0000
Subject: [PATCH 02/18] Works for value types and static functions.

---
 lib/Sema/TypeCheckConstraints.cpp | 19 ++++++++++++++-----
 lib/Sema/TypeCheckType.cpp        |  2 ++
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/lib/Sema/TypeCheckConstraints.cpp b/lib/Sema/TypeCheckConstraints.cpp
index b6fc8f8f31b7e..d400a25b53502 100644
--- a/lib/Sema/TypeCheckConstraints.cpp
+++ b/lib/Sema/TypeCheckConstraints.cpp
@@ -551,12 +551,21 @@ resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE, DeclContext *DC) {
     };
 
     if (!isConfused) {
-      if (Name.getBaseName().userFacingName() == "Self") {
-        DeclName selfName(Context.getIdentifier("self"));
-        auto selfInstance = lookupUnqualified(DC, selfName, Loc, lookupOptions);
-        if (!selfInstance.empty()) {
-          ValueDecl *D = selfInstance.front().getValueDecl();
+      if (Name == Context.Id_Self) {
+//        return new (Context) TypeExpr(TypeLoc::withoutLoc(
+//            DynamicSelfType::get(
+//              DC->getInnermostTypeContext()
+//                                 ->getSelfTypeInContext()
+//                                 //->getDeclaredInterfaceType()
+//                                 , Context)));
+        auto selfs = lookupUnqualified(DC, Context.Id_self, Loc, lookupOptions);
+        if (!selfs.empty()) {
+          ValueDecl *D = selfs.front().getValueDecl();
           Expr *E = new (Context) DeclRefExpr(D, nameLoc, /*Implicit=*/false);
+          if (auto func = dyn_cast<AbstractFunctionDecl>(
+                                        DC->getInnermostMethodContext()))
+            if (func->isStatic())
+              return E;
           return new (Context) DynamicTypeExpr(Loc, Loc, E, Loc, Type());
         }
       }
diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index a61611f8d96a7..5d84c30d08608 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1061,6 +1061,8 @@ static Type diagnoseUnknownType(TypeResolution resolution,
         // type. Fix this by replacing 'Self' with the nominal type name.
         assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
 
+        return nominal->getDeclaredInterfaceType();
+
         // Produce a Fix-It replacing 'Self' with the nominal type name.
         auto name = getDeclNameFromContext(dc, nominal);
         diags.diagnose(comp->getIdLoc(), diag::self_in_nominal, name)

From 598dcffd2092ea9ca7b08e1295b9cb43654f43f1 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Wed, 27 Feb 2019 21:29:38 +0000
Subject: [PATCH 03/18] Further experiments with TypeExpr

---
 lib/Sema/TypeCheckConstraints.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/Sema/TypeCheckConstraints.cpp b/lib/Sema/TypeCheckConstraints.cpp
index d400a25b53502..e739c0bbb9aee 100644
--- a/lib/Sema/TypeCheckConstraints.cpp
+++ b/lib/Sema/TypeCheckConstraints.cpp
@@ -558,6 +558,17 @@ resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE, DeclContext *DC) {
 //                                 ->getSelfTypeInContext()
 //                                 //->getDeclaredInterfaceType()
 //                                 , Context)));
+//        return new (Context) TypeExpr(TypeLoc::withoutLoc(
+//            DC->getInnermostTypeContext()
+//                                 ->getSelfTypeInContext()));
+
+//        Type SelfType = DC->getInnermostTypeContext()->getSelfInterfaceType();
+//        if (ClassType::classof(SelfType.getPointer()))
+//          SelfType = DynamicSelfType::get(SelfType, Context);
+//        return new (Context) TypeExpr(TypeLoc(new (Context)
+//                FixedTypeRepr(DC//->getInnermostTypeContext()
+//                              ->mapTypeIntoContext(SelfType), Loc)));
+
         auto selfs = lookupUnqualified(DC, Context.Id_self, Loc, lookupOptions);
         if (!selfs.empty()) {
           ValueDecl *D = selfs.front().getValueDecl();

From 0de016ccf49538af0218796b1070b0cf0df9bf91 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Wed, 27 Feb 2019 22:59:04 +0000
Subject: [PATCH 04/18] Move Self processing off diagnostic path

---
 lib/Sema/TypeCheckType.cpp | 87 +++++++++-----------------------------
 1 file changed, 20 insertions(+), 67 deletions(-)

diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index 5d84c30d08608..f5b6b9f8051a8 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1002,36 +1002,6 @@ static Type resolveTypeDecl(TypeDecl *typeDecl, SourceLoc loc,
   return type;
 }
 
-static std::string getDeclNameFromContext(DeclContext *dc,
-                                          NominalTypeDecl *nominal) {
-  // We don't allow an unqualified reference to a type inside an
-  // extension if the type is itself nested inside another type,
-  // eg:
-  //
-  // extension A.B { ... B ... }
-  //
-  // Instead, you must write 'A.B'. Calculate the right name to use
-  // for fixits.
-  if (!isa<ExtensionDecl>(dc)) {
-    SmallVector<Identifier, 2> idents;
-    auto *parentNominal = nominal;
-    while (parentNominal != nullptr) {
-      idents.push_back(parentNominal->getName());
-      parentNominal = parentNominal->getDeclContext()->getSelfNominalTypeDecl();
-    }
-    std::reverse(idents.begin(), idents.end());
-    std::string result;
-    for (auto ident : idents) {
-      if (!result.empty())
-        result += ".";
-      result += ident.str();
-    }
-    return result;
-  } else {
-    return nominal->getName().str();
-  }
-}
-
 /// Diagnose a reference to an unknown type.
 ///
 /// This routine diagnoses a reference to an unknown type, and
@@ -1051,43 +1021,6 @@ static Type diagnoseUnknownType(TypeResolution resolution,
 
   // Unqualified lookup case.
   if (parentType.isNull()) {
-    if (comp->getIdentifier() == ctx.Id_Self &&
-        !isa<GenericIdentTypeRepr>(comp)) {
-      DeclContext *nominalDC = nullptr;
-      NominalTypeDecl *nominal = nullptr;
-      if ((nominalDC = dc->getInnermostTypeContext()) &&
-          (nominal = nominalDC->getSelfNominalTypeDecl())) {
-        // Attempt to refer to 'Self' within a non-protocol nominal
-        // type. Fix this by replacing 'Self' with the nominal type name.
-        assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
-
-        return nominal->getDeclaredInterfaceType();
-
-        // Produce a Fix-It replacing 'Self' with the nominal type name.
-        auto name = getDeclNameFromContext(dc, nominal);
-        diags.diagnose(comp->getIdLoc(), diag::self_in_nominal, name)
-          .fixItReplace(comp->getIdLoc(), name);
-
-        // If this is a requirement, replacing 'Self' with a valid type will
-        // result in additional unnecessary diagnostics (does not refer to a
-        // generic parameter or associated type). Simply return an error type.
-        if (options.is(TypeResolverContext::GenericRequirement))
-          return ErrorType::get(ctx);
-
-        auto type = resolution.mapTypeIntoContext(
-          dc->getInnermostTypeContext()->getSelfInterfaceType());
-
-        comp->overwriteIdentifier(nominal->getName());
-        comp->setValue(nominal, nominalDC->getParent());
-        return type;
-      }
-      // Attempt to refer to 'Self' from a free function.
-      diags.diagnose(comp->getIdLoc(), diag::dynamic_self_non_method,
-                     dc->getParent()->isLocalContext());
-
-      return ErrorType::get(ctx);
-    }
-
     // Try ignoring access control.
     DeclContext *lookupDC = dc;
     NameLookupOptions relookupOptions = lookupOptions;
@@ -1320,6 +1253,26 @@ resolveTopLevelIdentTypeComponent(TypeResolution resolution,
     return ErrorType::get(ctx);
   }
 
+  if (comp->getIdentifier() == ctx.Id_Self &&
+      !isa<GenericIdentTypeRepr>(comp)) {
+    DeclContext *nominalDC = nullptr;
+    NominalTypeDecl *nominal = nullptr;
+    auto dc = resolution.getDeclContext();
+    if ((nominalDC = dc->getInnermostTypeContext()) &&
+        (nominal = nominalDC->getSelfNominalTypeDecl())) {
+      // Attempt to refer to 'Self' within a non-protocol nominal
+      // type. Fix this by replacing 'Self' with the nominal type name.
+      assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
+
+      return nominal->getDeclaredInterfaceType();
+    }
+    // Attempt to refer to 'Self' from a free function.
+    diags.diagnose(comp->getIdLoc(), diag::dynamic_self_non_method,
+                   dc->getParent()->isLocalContext());
+
+    return ErrorType::get(ctx);
+  }
+
   // If we found nothing, complain and give ourselves a chance to recover.
   if (current.isNull()) {
     // If we're not allowed to complain or we couldn't fix the

From 87880650b4f1e84010b1ad5c188e5248bf7ebf93 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Wed, 27 Feb 2019 22:59:31 +0000
Subject: [PATCH 05/18] diagnostic instead of assertion fail

---
 include/swift/AST/DiagnosticsSema.def | 3 +++
 lib/Sema/ConstraintSystem.cpp         | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index 6715b5295147e..c088afcff746a 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -162,6 +162,9 @@ ERROR(cannot_pass_rvalue_mutating_getter,none,
       "cannot use mutating getter on immutable value of type %0",
       (Type))
 
+ERROR(invalid_generic_context,none,
+      "generic type can not be used in this context", ())
+
 ERROR(expression_too_complex,none,
       "the compiler is unable to type-check this expression in reasonable time; "
       "try breaking up the expression into distinct sub-expressions", ())
diff --git a/lib/Sema/ConstraintSystem.cpp b/lib/Sema/ConstraintSystem.cpp
index 2412542f2c583..623e425478121 100644
--- a/lib/Sema/ConstraintSystem.cpp
+++ b/lib/Sema/ConstraintSystem.cpp
@@ -535,7 +535,10 @@ static void checkNestedTypeConstraints(ConstraintSystem &cs, Type type,
 
 Type ConstraintSystem::openUnboundGenericType(
     Type type, ConstraintLocatorBuilder locator) {
-  assert(!type->hasTypeParameter());
+  if (type->hasTypeParameter()) {
+    TC.diagnose(locator.getAnchor()->getLoc(), diag::invalid_generic_context);
+    return ErrorType::get(getASTContext());
+  }
 
   checkNestedTypeConstraints(*this, type, locator);
 

From c703a22cb9487c7318dc4c55e4559331ab6bcd04 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Fri, 1 Mar 2019 17:11:12 +0000
Subject: [PATCH 06/18] TypeExpr of DynamicSelfType now working.

---
 include/swift/AST/DiagnosticsSema.def |  2 +-
 lib/Sema/TypeCheckConstraints.cpp     | 22 ++++-----------
 lib/Sema/TypeCheckType.cpp            | 40 +++++++++++++--------------
 3 files changed, 27 insertions(+), 37 deletions(-)

diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index c088afcff746a..1e09ee1c34d58 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -163,7 +163,7 @@ ERROR(cannot_pass_rvalue_mutating_getter,none,
       (Type))
 
 ERROR(invalid_generic_context,none,
-      "generic type can not be used in this context", ())
+      "generic type cannot be used in this context", ())
 
 ERROR(expression_too_complex,none,
       "the compiler is unable to type-check this expression in reasonable time; "
diff --git a/lib/Sema/TypeCheckConstraints.cpp b/lib/Sema/TypeCheckConstraints.cpp
index e739c0bbb9aee..fa1b49b71959c 100644
--- a/lib/Sema/TypeCheckConstraints.cpp
+++ b/lib/Sema/TypeCheckConstraints.cpp
@@ -552,22 +552,12 @@ resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE, DeclContext *DC) {
 
     if (!isConfused) {
       if (Name == Context.Id_Self) {
-//        return new (Context) TypeExpr(TypeLoc::withoutLoc(
-//            DynamicSelfType::get(
-//              DC->getInnermostTypeContext()
-//                                 ->getSelfTypeInContext()
-//                                 //->getDeclaredInterfaceType()
-//                                 , Context)));
-//        return new (Context) TypeExpr(TypeLoc::withoutLoc(
-//            DC->getInnermostTypeContext()
-//                                 ->getSelfTypeInContext()));
-
-//        Type SelfType = DC->getInnermostTypeContext()->getSelfInterfaceType();
-//        if (ClassType::classof(SelfType.getPointer()))
-//          SelfType = DynamicSelfType::get(SelfType, Context);
-//        return new (Context) TypeExpr(TypeLoc(new (Context)
-//                FixedTypeRepr(DC//->getInnermostTypeContext()
-//                              ->mapTypeIntoContext(SelfType), Loc)));
+        Type SelfType = DC->getInnermostTypeContext()->getSelfInterfaceType();
+        if (SelfType->is<ClassType>() || SelfType->is<BoundGenericClassType>())
+          SelfType = DynamicSelfType::get(SelfType, Context);
+        SelfType = DC->mapTypeIntoContext(SelfType);
+        return new (Context) TypeExpr(TypeLoc(new (Context)
+                FixedTypeRepr(SelfType, Loc), SelfType));
 
         auto selfs = lookupUnqualified(DC, Context.Id_self, Loc, lookupOptions);
         if (!selfs.empty()) {
diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index f5b6b9f8051a8..ad3a4954684c6 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1253,28 +1253,28 @@ resolveTopLevelIdentTypeComponent(TypeResolution resolution,
     return ErrorType::get(ctx);
   }
 
-  if (comp->getIdentifier() == ctx.Id_Self &&
-      !isa<GenericIdentTypeRepr>(comp)) {
-    DeclContext *nominalDC = nullptr;
-    NominalTypeDecl *nominal = nullptr;
-    auto dc = resolution.getDeclContext();
-    if ((nominalDC = dc->getInnermostTypeContext()) &&
-        (nominal = nominalDC->getSelfNominalTypeDecl())) {
-      // Attempt to refer to 'Self' within a non-protocol nominal
-      // type. Fix this by replacing 'Self' with the nominal type name.
-      assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
-
-      return nominal->getDeclaredInterfaceType();
-    }
-    // Attempt to refer to 'Self' from a free function.
-    diags.diagnose(comp->getIdLoc(), diag::dynamic_self_non_method,
-                   dc->getParent()->isLocalContext());
-
-    return ErrorType::get(ctx);
-  }
-
   // If we found nothing, complain and give ourselves a chance to recover.
   if (current.isNull()) {
+    if (comp->getIdentifier() == ctx.Id_Self &&
+        !isa<GenericIdentTypeRepr>(comp)) {
+      DeclContext *nominalDC = nullptr;
+      NominalTypeDecl *nominal = nullptr;
+      auto dc = resolution.getDeclContext();
+      if ((nominalDC = dc->getInnermostTypeContext()) &&
+          (nominal = nominalDC->getSelfNominalTypeDecl())) {
+        // Attempt to refer to 'Self' within a non-protocol nominal
+        // type. Fix this by replacing 'Self' with the nominal type name.
+        assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
+
+        return nominal->getDeclaredInterfaceType();
+      }
+      // Attempt to refer to 'Self' from a free function.
+      diags.diagnose(comp->getIdLoc(), diag::dynamic_self_non_method,
+                     dc->getParent()->isLocalContext());
+
+      return ErrorType::get(ctx);
+    }
+
     // If we're not allowed to complain or we couldn't fix the
     // source, bail out.
     if (options.contains(TypeResolutionFlags::SilenceErrors))

From 49548917b61d9b5f0ac1993802290be706a1d369 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Fri, 1 Mar 2019 19:00:11 +0000
Subject: [PATCH 07/18] Update tests for availability of Self

---
 lib/Sema/ConstraintSystem.cpp       |  4 +-
 lib/Sema/TypeCheckConstraints.cpp   | 24 ++++------
 lib/Sema/TypeCheckType.cpp          | 10 ++--
 test/decl/ext/generic.swift         |  2 +-
 test/decl/func/dynamic_self.swift   | 74 ++++++++++++++++++++++-------
 test/decl/nested/type_in_type.swift |  1 -
 test/type/self.swift                |  8 ++--
 7 files changed, 79 insertions(+), 44 deletions(-)

diff --git a/lib/Sema/ConstraintSystem.cpp b/lib/Sema/ConstraintSystem.cpp
index 623e425478121..bb2d928ac6702 100644
--- a/lib/Sema/ConstraintSystem.cpp
+++ b/lib/Sema/ConstraintSystem.cpp
@@ -536,7 +536,9 @@ static void checkNestedTypeConstraints(ConstraintSystem &cs, Type type,
 Type ConstraintSystem::openUnboundGenericType(
     Type type, ConstraintLocatorBuilder locator) {
   if (type->hasTypeParameter()) {
-    TC.diagnose(locator.getAnchor()->getLoc(), diag::invalid_generic_context);
+    auto castExpr = dyn_cast<ExplicitCastExpr>(locator.getAnchor());
+    TC.diagnose(castExpr ? castExpr->getCastTypeLoc().getLoc() :
+                locator.getAnchor()->getLoc(), diag::invalid_generic_context);
     return ErrorType::get(getASTContext());
   }
 
diff --git a/lib/Sema/TypeCheckConstraints.cpp b/lib/Sema/TypeCheckConstraints.cpp
index fa1b49b71959c..eac1970b15549 100644
--- a/lib/Sema/TypeCheckConstraints.cpp
+++ b/lib/Sema/TypeCheckConstraints.cpp
@@ -552,22 +552,14 @@ resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE, DeclContext *DC) {
 
     if (!isConfused) {
       if (Name == Context.Id_Self) {
-        Type SelfType = DC->getInnermostTypeContext()->getSelfInterfaceType();
-        if (SelfType->is<ClassType>() || SelfType->is<BoundGenericClassType>())
-          SelfType = DynamicSelfType::get(SelfType, Context);
-        SelfType = DC->mapTypeIntoContext(SelfType);
-        return new (Context) TypeExpr(TypeLoc(new (Context)
-                FixedTypeRepr(SelfType, Loc), SelfType));
-
-        auto selfs = lookupUnqualified(DC, Context.Id_self, Loc, lookupOptions);
-        if (!selfs.empty()) {
-          ValueDecl *D = selfs.front().getValueDecl();
-          Expr *E = new (Context) DeclRefExpr(D, nameLoc, /*Implicit=*/false);
-          if (auto func = dyn_cast<AbstractFunctionDecl>(
-                                        DC->getInnermostMethodContext()))
-            if (func->isStatic())
-              return E;
-          return new (Context) DynamicTypeExpr(Loc, Loc, E, Loc, Type());
+        if (DeclContext *typeContext = DC->getInnermostTypeContext()){
+          Type SelfType = typeContext->getSelfInterfaceType();
+
+          if (typeContext->getSelfClassDecl())
+            SelfType = DynamicSelfType::get(SelfType, Context);
+          SelfType = DC->mapTypeIntoContext(SelfType);
+          return new (Context) TypeExpr(TypeLoc(new (Context)
+                                                FixedTypeRepr(SelfType, Loc)));
         }
       }
 
diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index ad3a4954684c6..4f8de787473d9 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1255,6 +1255,11 @@ resolveTopLevelIdentTypeComponent(TypeResolution resolution,
 
   // If we found nothing, complain and give ourselves a chance to recover.
   if (current.isNull()) {
+    // If we're not allowed to complain or we couldn't fix the
+    // source, bail out.
+    if (options.contains(TypeResolutionFlags::SilenceErrors))
+      return ErrorType::get(ctx);
+
     if (comp->getIdentifier() == ctx.Id_Self &&
         !isa<GenericIdentTypeRepr>(comp)) {
       DeclContext *nominalDC = nullptr;
@@ -1275,11 +1280,6 @@ resolveTopLevelIdentTypeComponent(TypeResolution resolution,
       return ErrorType::get(ctx);
     }
 
-    // If we're not allowed to complain or we couldn't fix the
-    // source, bail out.
-    if (options.contains(TypeResolutionFlags::SilenceErrors))
-      return ErrorType::get(ctx);
-
     return diagnoseUnknownType(resolution, nullptr, SourceRange(), comp,
                                options, lookupOptions);
   }
diff --git a/test/decl/ext/generic.swift b/test/decl/ext/generic.swift
index 66327d330c270..8a539153c3bd1 100644
--- a/test/decl/ext/generic.swift
+++ b/test/decl/ext/generic.swift
@@ -149,7 +149,7 @@ extension Array where Element == String { }
 extension GenericClass : P3 where T : P3 { }
 
 extension GenericClass where Self : P3 { }
-// expected-error@-1{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'GenericClass'?}} {{30-34=GenericClass}}
+// expected-error@-1{{type 'GenericClass<T>' in conformance requirement does not refer to a generic parameter or associated type}}
 
 protocol P4 {
   associatedtype T
diff --git a/test/decl/func/dynamic_self.swift b/test/decl/func/dynamic_self.swift
index be2aaa4d477d7..b04b941e1b6fc 100644
--- a/test/decl/func/dynamic_self.swift
+++ b/test/decl/func/dynamic_self.swift
@@ -10,23 +10,23 @@ func inFunction() {
 }
 
 struct S0 {
-  func f() -> Self { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'S0'?}}{{15-19=S0}}
+  func f() -> Self { }
 
-  func g(_ ds: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'S0'?}}{{16-20=S0}}
+  func g(_ ds: Self) { }
 }
 
 enum E0 {
-  func f() -> Self { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'E0'?}}{{15-19=E0}}
+  func f() -> Self { }
 
-  func g(_ ds: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'E0'?}}{{16-20=E0}}
+  func g(_ ds: Self) { }
 }
 
 class C0 {
   func f() -> Self { } // okay
 
-  func g(_ ds: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C0'?}}{{16-20=C0}}
+  func g(_ ds: Self) { }
 
-  func h(_ ds: Self) -> Self { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C0'?}}{{16-20=C0}}
+  func h(_ ds: Self) -> Self { }
 }
 
 protocol P0 {
@@ -73,7 +73,7 @@ class C1 {
     if !b { return type(of: self).init(int: 5) }
 
     // Can't utter Self within the body of a method.
-    var _: Self = self // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C1'?}} {{12-16=C1}}
+    var _: Self = self
 
     // Okay to return 'self', because it has the appropriate type.
     return self // okay
@@ -85,11 +85,11 @@ class C1 {
     var x: Int = self // expected-error{{cannot convert value of type 'Self.Type' to specified type 'Int'}}
 
     // Can't utter Self within the body of a method.
-    var c1 = C1(int: 5) as Self // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C1'?}} {{28-32=C1}}
+    var c1 = C1(int: 5) as Self
 
     if b { return self.init(int: 5) }
 
-    return Self() // expected-error{{non-nominal type 'Self.Type' does not support explicit initialization}}
+    return Self() // expected-error{{non-nominal type 'Self' does not support explicit initialization}}
   }
 
   // This used to crash because metatype construction went down a
@@ -419,27 +419,29 @@ func useSelfOperator() {
 class A<T> {
   let b: Int
   required init(a: Int) {
-    print("\(Self).\(#function)")
+    print("\(Self.self).\(#function)")
+    Self.y()
     b = a
   }
   static func z() {
     print("\(Self.self).\(#function)")
   }
   class func y() {
-    print("\(Self).\(#function)")
+    print("\(Self.self).\(#function)")
+    Self.z()
   }
-  func x() {
+  func x() -> A? {
     print("\(Self.self).\(#function)")
     Self.y()
     Self.z()
-    _ = Self.init(a: 77)
+    return Self.init(a: 77)
   }
 }
 
 class B: A<Int> {
   let a: Int
   required convenience init(a: Int) {
-    print("\(Self).\(#function)")
+    print("\(Self.self).\(#function)")
     self.init()
   }
   init() {
@@ -450,8 +452,48 @@ class B: A<Int> {
     super.init(a: 88)
   }
   override class func y() {
-    print("\(Self).\(#function)")
+    print("override \(Self.self).\(#function)")
+  }
+}
+
+struct S2 {
+  let x = 99
+  static func x() {
+    Self.y()
+  }
+  static func y() {
+    print("y()")
+  }
+  func foo(a: [Self]) -> Self? {
+    Self.x()
+    return Self.init() as Self
+  }
+}
+
+struct S3<T> {
+  let x = 99
+  static func x() {
+    Self.y()
+  }
+  static func y() {
+    print("y()")
+  }
+  func foo(a: [Self]) -> Self? {
+    Self.x()
+    return Self.init() as? Self
+    // expected-error@-1 {{cannot convert return expression of type 'S3<T>?' to return type 'S3<T>?'}}
+    // expected-error@-2 {{generic type cannot be used in this context}}
+    // expected-error@-3 {{generic type cannot be used in this context}}
   }
 }
 
-B().x()
+enum E {
+  static func f() {
+    print("f()")
+  }
+  case e
+  func h(h: Self) -> Self {
+    Self.f()
+    return .e
+  }
+}
diff --git a/test/decl/nested/type_in_type.swift b/test/decl/nested/type_in_type.swift
index 6543b11344d78..6945639a0afda 100644
--- a/test/decl/nested/type_in_type.swift
+++ b/test/decl/nested/type_in_type.swift
@@ -417,7 +417,6 @@ extension OuterGeneric.MidNonGeneric {
   }
 
   func doMoreStuffWrong() -> Self {
-    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'OuterGeneric.MidNonGeneric'?}}
 
   }
 }
diff --git a/test/type/self.swift b/test/type/self.swift
index 815842946a6ea..9108f563894a8 100644
--- a/test/type/self.swift
+++ b/test/type/self.swift
@@ -1,15 +1,15 @@
 // RUN: %target-typecheck-verify-swift -swift-version 5
 
 struct S0<T> {
-  func foo(_ other: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'S0'?}}{{21-25=S0}}
+  func foo(_ other: Self) { }
 }
 
 class C0<T> {
-  func foo(_ other: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C0'?}}{{21-25=C0}}
+  func foo(_ other: Self) { }
 }
 
 enum E0<T> {
-  func foo(_ other: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'E0'?}}{{21-25=E0}}
+  func foo(_ other: Self) { }
 }
 
 // rdar://problem/21745221
@@ -23,7 +23,7 @@ extension X {
 }
 
 extension X.Inner {
-  func foo(_ other: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'X.Inner'?}}{{21-25=X.Inner}}
+  func foo(_ other: Self) { }
 }
 
 // SR-695

From 588b6509e5585dc8fa70bb448bc3b8dafbb061cb Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Wed, 6 Mar 2019 12:40:46 +0000
Subject: [PATCH 08/18] Cast to Self fixed!

---
 include/swift/AST/DiagnosticsSema.def |  3 -
 lib/Sema/ConstraintSystem.cpp         |  7 +-
 lib/Sema/TypeCheckType.cpp            | 11 ++-
 test/decl/func/dynamic_self.swift     | 86 +-----------------------
 test/type/self.swift                  | 96 +++++++++++++++++++++++++++
 5 files changed, 106 insertions(+), 97 deletions(-)

diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index 1e09ee1c34d58..6715b5295147e 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -162,9 +162,6 @@ ERROR(cannot_pass_rvalue_mutating_getter,none,
       "cannot use mutating getter on immutable value of type %0",
       (Type))
 
-ERROR(invalid_generic_context,none,
-      "generic type cannot be used in this context", ())
-
 ERROR(expression_too_complex,none,
       "the compiler is unable to type-check this expression in reasonable time; "
       "try breaking up the expression into distinct sub-expressions", ())
diff --git a/lib/Sema/ConstraintSystem.cpp b/lib/Sema/ConstraintSystem.cpp
index bb2d928ac6702..2412542f2c583 100644
--- a/lib/Sema/ConstraintSystem.cpp
+++ b/lib/Sema/ConstraintSystem.cpp
@@ -535,12 +535,7 @@ static void checkNestedTypeConstraints(ConstraintSystem &cs, Type type,
 
 Type ConstraintSystem::openUnboundGenericType(
     Type type, ConstraintLocatorBuilder locator) {
-  if (type->hasTypeParameter()) {
-    auto castExpr = dyn_cast<ExplicitCastExpr>(locator.getAnchor());
-    TC.diagnose(castExpr ? castExpr->getCastTypeLoc().getLoc() :
-                locator.getAnchor()->getLoc(), diag::invalid_generic_context);
-    return ErrorType::get(getASTContext());
-  }
+  assert(!type->hasTypeParameter());
 
   checkNestedTypeConstraints(*this, type, locator);
 
diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index 4f8de787473d9..2a297ae656110 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1267,11 +1267,16 @@ resolveTopLevelIdentTypeComponent(TypeResolution resolution,
       auto dc = resolution.getDeclContext();
       if ((nominalDC = dc->getInnermostTypeContext()) &&
           (nominal = nominalDC->getSelfNominalTypeDecl())) {
-        // Attempt to refer to 'Self' within a non-protocol nominal
-        // type. Fix this by replacing 'Self' with the nominal type name.
         assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
 
-        return nominal->getDeclaredInterfaceType();
+        Type SelfType = nominal->getDeclaredInterfaceType();
+
+// Causes assertion failure:
+// Assertion failed: (hasSelfMetadataParam() && "This method can only be called if the " "SILFunction has a self-metadata parameter"), function getSelfMetadataArgument, file /Volumes/Elements/swift-self/swift/include/swift/SIL/SILFunction.h, line 935.
+//        if (nominalDC->getSelfClassDecl())
+//          SelfType = DynamicSelfType::get(SelfType, ctx);
+
+        return resolution.mapTypeIntoContext(SelfType);
       }
       // Attempt to refer to 'Self' from a free function.
       diags.diagnose(comp->getIdLoc(), diag::dynamic_self_non_method,
diff --git a/test/decl/func/dynamic_self.swift b/test/decl/func/dynamic_self.swift
index b04b941e1b6fc..26a44c01e84f4 100644
--- a/test/decl/func/dynamic_self.swift
+++ b/test/decl/func/dynamic_self.swift
@@ -412,88 +412,4 @@ class SelfOperator {
 func useSelfOperator() {
   let s = SelfOperator()
   _ = s + s
-}
-
-// These references to Self are now possible
-
-class A<T> {
-  let b: Int
-  required init(a: Int) {
-    print("\(Self.self).\(#function)")
-    Self.y()
-    b = a
-  }
-  static func z() {
-    print("\(Self.self).\(#function)")
-  }
-  class func y() {
-    print("\(Self.self).\(#function)")
-    Self.z()
-  }
-  func x() -> A? {
-    print("\(Self.self).\(#function)")
-    Self.y()
-    Self.z()
-    return Self.init(a: 77)
-  }
-}
-
-class B: A<Int> {
-  let a: Int
-  required convenience init(a: Int) {
-    print("\(Self.self).\(#function)")
-    self.init()
-  }
-  init() {
-    print("\(Self.self).\(#function)")
-    Self.y()
-    Self.z()
-    a = 99
-    super.init(a: 88)
-  }
-  override class func y() {
-    print("override \(Self.self).\(#function)")
-  }
-}
-
-struct S2 {
-  let x = 99
-  static func x() {
-    Self.y()
-  }
-  static func y() {
-    print("y()")
-  }
-  func foo(a: [Self]) -> Self? {
-    Self.x()
-    return Self.init() as Self
-  }
-}
-
-struct S3<T> {
-  let x = 99
-  static func x() {
-    Self.y()
-  }
-  static func y() {
-    print("y()")
-  }
-  func foo(a: [Self]) -> Self? {
-    Self.x()
-    return Self.init() as? Self
-    // expected-error@-1 {{cannot convert return expression of type 'S3<T>?' to return type 'S3<T>?'}}
-    // expected-error@-2 {{generic type cannot be used in this context}}
-    // expected-error@-3 {{generic type cannot be used in this context}}
-  }
-}
-
-enum E {
-  static func f() {
-    print("f()")
-  }
-  case e
-  func h(h: Self) -> Self {
-    Self.f()
-    return .e
-  }
-}
+}
\ No newline at end of file
diff --git a/test/type/self.swift b/test/type/self.swift
index 9108f563894a8..0858bfeb71c34 100644
--- a/test/type/self.swift
+++ b/test/type/self.swift
@@ -43,3 +43,99 @@ final class FinalMario : Mario {
     }
 }
 
+// These references to Self are now possible (SE-0068)
+
+class A<T> {
+  let b: Int
+  required init(a: Int) {
+    print("\(Self.self).\(#function)")
+    Self.y()
+    b = a
+  }
+  static func z(n: Self? = nil) {
+    print("\(Self.self).\(#function)")
+  }
+  class func y() {
+    print("\(Self.self).\(#function)")
+    Self.z()
+  }
+  func x() -> A? {
+    print("\(Self.self).\(#function)")
+    Self.y()
+    Self.z()
+    let _: Self = Self.init(a: 66)
+    return Self.init(a: 77) as? Self as? A
+    // expected-warning@-1 {{conditional cast from 'Self' to 'A<T>' always succeeds}}
+    // expected-warning@-2 {{conditional downcast from 'A<T>?' to 'A<T>' does nothing}}
+  }
+}
+
+class B: A<Int> {
+  let a: Int
+  required convenience init(a: Int) {
+    print("\(Self.self).\(#function)")
+    self.init()
+  }
+  init() {
+    print("\(Self.self).\(#function)")
+    Self.y()
+    Self.z()
+    a = 99
+    super.init(a: 88)
+  }
+  override class func y() {
+    print("override \(Self.self).\(#function)")
+  }
+}
+
+class C {
+  required init() {
+  }
+  func g() {
+    _ = Self.init() as? Self
+    // expected-warning@-1 {{conditional cast from 'Self' to 'C' always succeeds}}
+  }
+}
+
+struct S2 {
+  let x = 99
+  struct S3<T> {
+    let x = 99
+    static func x() {
+      Self.y()
+    }
+    static func y() {
+      print("HERE")
+    }
+    func foo(a: [Self]) -> Self? {
+      Self.x()
+      return Self.init() as? Self
+      // expected-warning@-1 {{conditional cast from 'S2.S3<T>' to 'S2.S3<T>' always succeeds}}
+    }
+  }
+}
+
+extension S2 {
+  static func x() {
+    Self.y()
+  }
+  static func y() {
+    print("HERE")
+  }
+  func foo(a: [Self]) -> Self? {
+    Self.x()
+    return Self.init() as? Self
+    // expected-warning@-1 {{conditional cast from 'S2' to 'S2' always succeeds}}
+  }
+}
+
+enum E {
+  static func f() {
+    print("f()")
+  }
+  case e
+  func h(h: Self) -> Self {
+    Self.f()
+    return .e
+  }
+}

From 42220dc197ddf81152012275ef1e4c88ad68cf20 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Thu, 7 Mar 2019 14:08:53 +0000
Subject: [PATCH 09/18] Self not available as type in classes except for return
 type

---
 lib/Sema/TypeCheckType.cpp        | 94 +++++++++++++++++++++++--------
 test/decl/ext/generic.swift       |  2 +-
 test/decl/func/dynamic_self.swift | 10 ++--
 test/type/self.swift              | 12 ++--
 4 files changed, 83 insertions(+), 35 deletions(-)

diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index 2a297ae656110..185704f2aa2f5 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1002,6 +1002,36 @@ static Type resolveTypeDecl(TypeDecl *typeDecl, SourceLoc loc,
   return type;
 }
 
+static std::string getDeclNameFromContext(DeclContext *dc,
+                                          NominalTypeDecl *nominal) {
+  // We don't allow an unqualified reference to a type inside an
+  // extension if the type is itself nested inside another type,
+  // eg:
+  //
+  // extension A.B { ... B ... }
+  //
+  // Instead, you must write 'A.B'. Calculate the right name to use
+  // for fixits.
+  if (!isa<ExtensionDecl>(dc)) {
+    SmallVector<Identifier, 2> idents;
+    auto *parentNominal = nominal;
+    while (parentNominal != nullptr) {
+      idents.push_back(parentNominal->getName());
+      parentNominal = parentNominal->getDeclContext()->getSelfNominalTypeDecl();
+    }
+    std::reverse(idents.begin(), idents.end());
+    std::string result;
+    for (auto ident : idents) {
+      if (!result.empty())
+        result += ".";
+      result += ident.str();
+    }
+    return result;
+  } else {
+    return nominal->getName().str();
+  }
+}
+
 /// Diagnose a reference to an unknown type.
 ///
 /// This routine diagnoses a reference to an unknown type, and
@@ -1021,6 +1051,45 @@ static Type diagnoseUnknownType(TypeResolution resolution,
 
   // Unqualified lookup case.
   if (parentType.isNull()) {
+    if (comp->getIdentifier() == ctx.Id_Self &&
+        !isa<GenericIdentTypeRepr>(comp)) {
+      DeclContext *nominalDC = nullptr;
+      NominalTypeDecl *nominal = nullptr;
+      if ((nominalDC = dc->getInnermostTypeContext()) &&
+          (nominal = nominalDC->getSelfNominalTypeDecl())) {
+        // Attempt to refer to 'Self' within a non-protocol nominal
+        // type. Fix this by replacing 'Self' with the nominal type name.
+        assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
+
+        if (!nominalDC->getSelfClassDecl())
+          return resolution.mapTypeIntoContext(nominal
+                                               ->getDeclaredInterfaceType());
+
+        // Produce a Fix-It replacing 'Self' with the nominal type name.
+        auto name = getDeclNameFromContext(dc, nominal);
+        diags.diagnose(comp->getIdLoc(), diag::self_in_nominal, name)
+          .fixItReplace(comp->getIdLoc(), name);
+
+        // If this is a requirement, replacing 'Self' with a valid type will
+        // result in additional unnecessary diagnostics (does not refer to a
+        // generic parameter or associated type). Simply return an error type.
+        if (options.is(TypeResolverContext::GenericRequirement))
+          return ErrorType::get(ctx);
+
+        auto type = resolution.mapTypeIntoContext(
+          dc->getInnermostTypeContext()->getSelfInterfaceType());
+
+        comp->overwriteIdentifier(nominal->getName());
+        comp->setValue(nominal, nominalDC->getParent());
+        return type;
+      }
+      // Attempt to refer to 'Self' from a free function.
+      diags.diagnose(comp->getIdLoc(), diag::dynamic_self_non_method,
+                     dc->getParent()->isLocalContext());
+
+      return ErrorType::get(ctx);
+    }
+
     // Try ignoring access control.
     DeclContext *lookupDC = dc;
     NameLookupOptions relookupOptions = lookupOptions;
@@ -1260,31 +1329,6 @@ resolveTopLevelIdentTypeComponent(TypeResolution resolution,
     if (options.contains(TypeResolutionFlags::SilenceErrors))
       return ErrorType::get(ctx);
 
-    if (comp->getIdentifier() == ctx.Id_Self &&
-        !isa<GenericIdentTypeRepr>(comp)) {
-      DeclContext *nominalDC = nullptr;
-      NominalTypeDecl *nominal = nullptr;
-      auto dc = resolution.getDeclContext();
-      if ((nominalDC = dc->getInnermostTypeContext()) &&
-          (nominal = nominalDC->getSelfNominalTypeDecl())) {
-        assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
-
-        Type SelfType = nominal->getDeclaredInterfaceType();
-
-// Causes assertion failure:
-// Assertion failed: (hasSelfMetadataParam() && "This method can only be called if the " "SILFunction has a self-metadata parameter"), function getSelfMetadataArgument, file /Volumes/Elements/swift-self/swift/include/swift/SIL/SILFunction.h, line 935.
-//        if (nominalDC->getSelfClassDecl())
-//          SelfType = DynamicSelfType::get(SelfType, ctx);
-
-        return resolution.mapTypeIntoContext(SelfType);
-      }
-      // Attempt to refer to 'Self' from a free function.
-      diags.diagnose(comp->getIdLoc(), diag::dynamic_self_non_method,
-                     dc->getParent()->isLocalContext());
-
-      return ErrorType::get(ctx);
-    }
-
     return diagnoseUnknownType(resolution, nullptr, SourceRange(), comp,
                                options, lookupOptions);
   }
diff --git a/test/decl/ext/generic.swift b/test/decl/ext/generic.swift
index 8a539153c3bd1..66327d330c270 100644
--- a/test/decl/ext/generic.swift
+++ b/test/decl/ext/generic.swift
@@ -149,7 +149,7 @@ extension Array where Element == String { }
 extension GenericClass : P3 where T : P3 { }
 
 extension GenericClass where Self : P3 { }
-// expected-error@-1{{type 'GenericClass<T>' in conformance requirement does not refer to a generic parameter or associated type}}
+// expected-error@-1{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'GenericClass'?}} {{30-34=GenericClass}}
 
 protocol P4 {
   associatedtype T
diff --git a/test/decl/func/dynamic_self.swift b/test/decl/func/dynamic_self.swift
index 26a44c01e84f4..944654a7d083c 100644
--- a/test/decl/func/dynamic_self.swift
+++ b/test/decl/func/dynamic_self.swift
@@ -24,9 +24,9 @@ enum E0 {
 class C0 {
   func f() -> Self { } // okay
 
-  func g(_ ds: Self) { }
+  func g(_ ds: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C0'?}}{{16-20=C0}}
 
-  func h(_ ds: Self) -> Self { }
+  func h(_ ds: Self) -> Self { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C0'?}}{{16-20=C0}}
 }
 
 protocol P0 {
@@ -73,7 +73,7 @@ class C1 {
     if !b { return type(of: self).init(int: 5) }
 
     // Can't utter Self within the body of a method.
-    var _: Self = self
+    var _: Self = self // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C1'?}} {{12-16=C1}}
 
     // Okay to return 'self', because it has the appropriate type.
     return self // okay
@@ -85,7 +85,7 @@ class C1 {
     var x: Int = self // expected-error{{cannot convert value of type 'Self.Type' to specified type 'Int'}}
 
     // Can't utter Self within the body of a method.
-    var c1 = C1(int: 5) as Self
+    var c1 = C1(int: 5) as Self // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C1'?}} {{28-32=C1}}
 
     if b { return self.init(int: 5) }
 
@@ -412,4 +412,4 @@ class SelfOperator {
 func useSelfOperator() {
   let s = SelfOperator()
   _ = s + s
-}
\ No newline at end of file
+}
diff --git a/test/type/self.swift b/test/type/self.swift
index 0858bfeb71c34..11d27a4a7fe47 100644
--- a/test/type/self.swift
+++ b/test/type/self.swift
@@ -5,7 +5,7 @@ struct S0<T> {
 }
 
 class C0<T> {
-  func foo(_ other: Self) { }
+  func foo(_ other: Self) { } // expected-error {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C0'?}}
 }
 
 enum E0<T> {
@@ -53,6 +53,7 @@ class A<T> {
     b = a
   }
   static func z(n: Self? = nil) {
+    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'A'?}}
     print("\(Self.self).\(#function)")
   }
   class func y() {
@@ -64,9 +65,11 @@ class A<T> {
     Self.y()
     Self.z()
     let _: Self = Self.init(a: 66)
+    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'A'?}}
     return Self.init(a: 77) as? Self as? A
-    // expected-warning@-1 {{conditional cast from 'Self' to 'A<T>' always succeeds}}
-    // expected-warning@-2 {{conditional downcast from 'A<T>?' to 'A<T>' does nothing}}
+    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'A'?}}
+    // expected-warning@-2 {{conditional cast from 'Self' to 'A<T>' always succeeds}}
+    // expected-warning@-3 {{conditional downcast from 'A<T>?' to 'A<T>' does nothing}}
   }
 }
 
@@ -93,7 +96,8 @@ class C {
   }
   func g() {
     _ = Self.init() as? Self
-    // expected-warning@-1 {{conditional cast from 'Self' to 'C' always succeeds}}
+    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C'?}}
+    // expected-warning@-2 {{conditional cast from 'Self' to 'C' always succeeds}}
   }
 }
 

From 619eac4d05f84bd7e524927c6376ce2a5b9aa8a0 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Fri, 8 Mar 2019 09:24:20 +0000
Subject: [PATCH 10/18] Could it be this simple?

---
 lib/Sema/TypeCheckType.cpp        | 10 +++++++---
 test/decl/func/dynamic_self.swift |  4 ++--
 test/type/self.swift              | 11 ++++-------
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index 185704f2aa2f5..8caeb4055a2f4 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1061,9 +1061,13 @@ static Type diagnoseUnknownType(TypeResolution resolution,
         // type. Fix this by replacing 'Self' with the nominal type name.
         assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
 
-        if (!nominalDC->getSelfClassDecl())
-          return resolution.mapTypeIntoContext(nominal
-                                               ->getDeclaredInterfaceType());
+        bool insideClass = nominalDC->getSelfClassDecl() != nullptr;
+        if (!insideClass || options.isAnyExpr()) {
+          Type SelfType = nominal->getSelfInterfaceType();
+          if (insideClass)
+            SelfType = DynamicSelfType::get(SelfType, ctx);
+          return resolution.mapTypeIntoContext(SelfType);
+        }
 
         // Produce a Fix-It replacing 'Self' with the nominal type name.
         auto name = getDeclNameFromContext(dc, nominal);
diff --git a/test/decl/func/dynamic_self.swift b/test/decl/func/dynamic_self.swift
index 944654a7d083c..e399a6b831b0a 100644
--- a/test/decl/func/dynamic_self.swift
+++ b/test/decl/func/dynamic_self.swift
@@ -73,7 +73,7 @@ class C1 {
     if !b { return type(of: self).init(int: 5) }
 
     // Can't utter Self within the body of a method.
-    var _: Self = self // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C1'?}} {{12-16=C1}}
+    var _: Self = self
 
     // Okay to return 'self', because it has the appropriate type.
     return self // okay
@@ -85,7 +85,7 @@ class C1 {
     var x: Int = self // expected-error{{cannot convert value of type 'Self.Type' to specified type 'Int'}}
 
     // Can't utter Self within the body of a method.
-    var c1 = C1(int: 5) as Self // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C1'?}} {{28-32=C1}}
+    var c1 = C1(int: 5) as Self // expected-error{{'C1' is not convertible to 'Self'; did you mean to use 'as!' to force downcast?}}
 
     if b { return self.init(int: 5) }
 
diff --git a/test/type/self.swift b/test/type/self.swift
index 11d27a4a7fe47..569998d410775 100644
--- a/test/type/self.swift
+++ b/test/type/self.swift
@@ -5,7 +5,7 @@ struct S0<T> {
 }
 
 class C0<T> {
-  func foo(_ other: Self) { } // expected-error {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C0'?}}
+  func foo(_ other: Self) { } // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C0'?}}{{21-25=C0}}
 }
 
 enum E0<T> {
@@ -65,11 +65,9 @@ class A<T> {
     Self.y()
     Self.z()
     let _: Self = Self.init(a: 66)
-    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'A'?}}
     return Self.init(a: 77) as? Self as? A
-    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'A'?}}
-    // expected-warning@-2 {{conditional cast from 'Self' to 'A<T>' always succeeds}}
-    // expected-warning@-3 {{conditional downcast from 'A<T>?' to 'A<T>' does nothing}}
+    // expected-warning@-1 {{conditional cast from 'Self' to 'Self' always succeeds}}
+    // expected-warning@-2 {{conditional downcast from 'Self?' to 'A<T>' is equivalent to an implicit conversion to an optional 'A<T>'}}
   }
 }
 
@@ -96,8 +94,7 @@ class C {
   }
   func g() {
     _ = Self.init() as? Self
-    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C'?}}
-    // expected-warning@-2 {{conditional cast from 'Self' to 'C' always succeeds}}
+    // expected-warning@-1 {{conditional cast from 'Self' to 'Self' always succeeds}}
   }
 }
 

From 1eb98989f2f4beaf71f74efb378a399eae05a17a Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Wed, 13 Mar 2019 12:56:23 +0000
Subject: [PATCH 11/18] Nearly there

---
 lib/Sema/TypeCheckType.cpp | 2 +-
 test/type/self.swift       | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index 8caeb4055a2f4..b6022e08b215b 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1062,7 +1062,7 @@ static Type diagnoseUnknownType(TypeResolution resolution,
         assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
 
         bool insideClass = nominalDC->getSelfClassDecl() != nullptr;
-        if (!insideClass || options.isAnyExpr()) {
+        if (!insideClass || dc->isLocalContext() || options.isAnyExpr()) {
           Type SelfType = nominal->getSelfInterfaceType();
           if (insideClass)
             SelfType = DynamicSelfType::get(SelfType, ctx);
diff --git a/test/type/self.swift b/test/type/self.swift
index 569998d410775..3131004336126 100644
--- a/test/type/self.swift
+++ b/test/type/self.swift
@@ -92,6 +92,9 @@ class B: A<Int> {
 class C {
   required init() {
   }
+  func f() {
+    func g(_: Self) {}
+  }
   func g() {
     _ = Self.init() as? Self
     // expected-warning@-1 {{conditional cast from 'Self' to 'Self' always succeeds}}

From e9354261e5fac36d6596192f34f9d23e92c4bb76 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Wed, 13 Mar 2019 17:54:44 +0000
Subject: [PATCH 12/18] Fix function decls using Self inside methods.

---
 lib/AST/DeclContext.cpp           |  5 ++---
 lib/Sema/TypeCheckType.cpp        | 10 +++++++---
 test/decl/ext/generic.swift       |  2 +-
 test/decl/func/dynamic_self.swift |  2 +-
 test/type/self.swift              |  8 ++++++++
 5 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/lib/AST/DeclContext.cpp b/lib/AST/DeclContext.cpp
index 1951dd0e73dd6..33af8d76293dd 100644
--- a/lib/AST/DeclContext.cpp
+++ b/lib/AST/DeclContext.cpp
@@ -223,9 +223,8 @@ bool DeclContext::isTypeContext() const {
 DeclContext *DeclContext::getInnermostTypeContext() {
   auto dc = this;
   do {
-    if (auto decl = dc->getAsDecl())
-      if (isa<NominalTypeDecl>(decl) || isa<ExtensionDecl>(decl))
-        return dc;
+    if (dc->isTypeContext())
+      return dc;
   } while ((dc = dc->getParent()));
 
   return nullptr;
diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index b6022e08b215b..b56f6d387d27c 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1057,18 +1057,22 @@ static Type diagnoseUnknownType(TypeResolution resolution,
       NominalTypeDecl *nominal = nullptr;
       if ((nominalDC = dc->getInnermostTypeContext()) &&
           (nominal = nominalDC->getSelfNominalTypeDecl())) {
-        // Attempt to refer to 'Self' within a non-protocol nominal
-        // type. Fix this by replacing 'Self' with the nominal type name.
         assert(!isa<ProtocolDecl>(nominal) && "Cannot be a protocol");
 
         bool insideClass = nominalDC->getSelfClassDecl() != nullptr;
-        if (!insideClass || dc->isLocalContext() || options.isAnyExpr()) {
+        AbstractFunctionDecl *methodDecl = dc->getInnermostMethodContext();
+        bool declaringMethod = methodDecl &&
+          methodDecl->getDeclContext() == dc->getParentForLookup();
+
+        if (!insideClass || !declaringMethod ||
+            options.getBaseContext() == TypeResolverContext::ExplicitCastExpr) {
           Type SelfType = nominal->getSelfInterfaceType();
           if (insideClass)
             SelfType = DynamicSelfType::get(SelfType, ctx);
           return resolution.mapTypeIntoContext(SelfType);
         }
 
+        // Attempt to refer to 'Self' within a non-protocol nominal type.
         // Produce a Fix-It replacing 'Self' with the nominal type name.
         auto name = getDeclNameFromContext(dc, nominal);
         diags.diagnose(comp->getIdLoc(), diag::self_in_nominal, name)
diff --git a/test/decl/ext/generic.swift b/test/decl/ext/generic.swift
index 66327d330c270..95e655797b034 100644
--- a/test/decl/ext/generic.swift
+++ b/test/decl/ext/generic.swift
@@ -149,7 +149,7 @@ extension Array where Element == String { }
 extension GenericClass : P3 where T : P3 { }
 
 extension GenericClass where Self : P3 { }
-// expected-error@-1{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'GenericClass'?}} {{30-34=GenericClass}}
+// expected-error@-1{{type 'Self' in conformance requirement does not refer to a generic parameter or associated type}}
 
 protocol P4 {
   associatedtype T
diff --git a/test/decl/func/dynamic_self.swift b/test/decl/func/dynamic_self.swift
index e399a6b831b0a..c76ef458c62dd 100644
--- a/test/decl/func/dynamic_self.swift
+++ b/test/decl/func/dynamic_self.swift
@@ -73,7 +73,7 @@ class C1 {
     if !b { return type(of: self).init(int: 5) }
 
     // Can't utter Self within the body of a method.
-    var _: Self = self
+    var _: Self = self // expected-error{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'C1'?}} {{12-16=C1}}
 
     // Okay to return 'self', because it has the appropriate type.
     return self // okay
diff --git a/test/type/self.swift b/test/type/self.swift
index 3131004336126..0a9fea9611bc8 100644
--- a/test/type/self.swift
+++ b/test/type/self.swift
@@ -65,6 +65,7 @@ class A<T> {
     Self.y()
     Self.z()
     let _: Self = Self.init(a: 66)
+    // expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'A'?}}
     return Self.init(a: 77) as? Self as? A
     // expected-warning@-1 {{conditional cast from 'Self' to 'Self' always succeeds}}
     // expected-warning@-2 {{conditional downcast from 'Self?' to 'A<T>' is equivalent to an implicit conversion to an optional 'A<T>'}}
@@ -108,6 +109,9 @@ struct S2 {
     static func x() {
       Self.y()
     }
+    func f() {
+      func g(_: Self) {}
+    }
     static func y() {
       print("HERE")
     }
@@ -126,6 +130,9 @@ extension S2 {
   static func y() {
     print("HERE")
   }
+  func f() {
+    func g(_: Self) {}
+  }
   func foo(a: [Self]) -> Self? {
     Self.x()
     return Self.init() as? Self
@@ -135,6 +142,7 @@ extension S2 {
 
 enum E {
   static func f() {
+    func g(_: Self) {}
     print("f()")
   }
   case e

From ec32f041924e40d87edba6f27ba6b465376fa1d6 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Wed, 13 Mar 2019 19:50:18 +0000
Subject: [PATCH 13/18] Fix
 validation-test/compiler_crashers_2_fixed/0164-sr7989.swift

---
 validation-test/compiler_crashers_2_fixed/0164-sr7989.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/validation-test/compiler_crashers_2_fixed/0164-sr7989.swift b/validation-test/compiler_crashers_2_fixed/0164-sr7989.swift
index a15fd1e09fad5..1afbee83e2eef 100644
--- a/validation-test/compiler_crashers_2_fixed/0164-sr7989.swift
+++ b/validation-test/compiler_crashers_2_fixed/0164-sr7989.swift
@@ -8,4 +8,4 @@ struct Var<N> {}
 extension Var : P2 where N : P1 { }
 
 protocol P3 {}
-extension Var : P3 where Self : P2 {} // expected-error {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'Var'?}}
+extension Var : P3 where Self : P2 {} // expected-error {{type 'Var<N>' in conformance requirement does not refer to a generic parameter or associated type}}

From 988e565166228952f42b149fc223f21f08c56ca0 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Wed, 13 Mar 2019 20:42:15 +0000
Subject: [PATCH 14/18] Fix of
 ./validation-test/compiler_crashers_2_fixed/0179-rdar44963974.swift

---
 lib/Sema/TypeCheckType.cpp  | 5 +++--
 test/decl/ext/generic.swift | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index b56f6d387d27c..747a68506e087 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -1064,8 +1064,9 @@ static Type diagnoseUnknownType(TypeResolution resolution,
         bool declaringMethod = methodDecl &&
           methodDecl->getDeclContext() == dc->getParentForLookup();
 
-        if (!insideClass || !declaringMethod ||
-            options.getBaseContext() == TypeResolverContext::ExplicitCastExpr) {
+        if (((!insideClass || !declaringMethod) &&
+             !options.is(TypeResolverContext::GenericRequirement)) ||
+            options.is(TypeResolverContext::ExplicitCastExpr)) {
           Type SelfType = nominal->getSelfInterfaceType();
           if (insideClass)
             SelfType = DynamicSelfType::get(SelfType, ctx);
diff --git a/test/decl/ext/generic.swift b/test/decl/ext/generic.swift
index 95e655797b034..66327d330c270 100644
--- a/test/decl/ext/generic.swift
+++ b/test/decl/ext/generic.swift
@@ -149,7 +149,7 @@ extension Array where Element == String { }
 extension GenericClass : P3 where T : P3 { }
 
 extension GenericClass where Self : P3 { }
-// expected-error@-1{{type 'Self' in conformance requirement does not refer to a generic parameter or associated type}}
+// expected-error@-1{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'GenericClass'?}} {{30-34=GenericClass}}
 
 protocol P4 {
   associatedtype T

From f2dff1759e2f875107d02ed2c4ba9726b97c12ec Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Thu, 14 Mar 2019 00:10:38 +0000
Subject: [PATCH 15/18] "Un-fix"
 validation-test/compiler_crashers_2_fixed/0164-sr7989.swift

---
 validation-test/compiler_crashers_2_fixed/0164-sr7989.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/validation-test/compiler_crashers_2_fixed/0164-sr7989.swift b/validation-test/compiler_crashers_2_fixed/0164-sr7989.swift
index 1afbee83e2eef..a15fd1e09fad5 100644
--- a/validation-test/compiler_crashers_2_fixed/0164-sr7989.swift
+++ b/validation-test/compiler_crashers_2_fixed/0164-sr7989.swift
@@ -8,4 +8,4 @@ struct Var<N> {}
 extension Var : P2 where N : P1 { }
 
 protocol P3 {}
-extension Var : P3 where Self : P2 {} // expected-error {{type 'Var<N>' in conformance requirement does not refer to a generic parameter or associated type}}
+extension Var : P3 where Self : P2 {} // expected-error {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'Var'?}}

From 32fd3554fdd734a95fbb434d45a39c22a4fa54a0 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Thu, 14 Mar 2019 21:15:19 +0000
Subject: [PATCH 16/18] CHANGELOG entry

---
 CHANGELOG.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 80380e6f2f780..a9f65e4b91f25 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,13 @@ CHANGELOG
 
 </details>
 
+Swift 5.1
+---------
+
+* [SR-1340](https://bugs.swift.org/browse/SR-1340):
+
+`Self` can now be used inside member functions and for function arguments of structs and enums to refer to the containing type.
+
 Swift 5.0
 ---------
 

From ae4bf3526b7e301830355763e0bb159967ecbadc Mon Sep 17 00:00:00 2001
From: Ben Rimmington <me@benrimmington.com>
Date: Thu, 14 Mar 2019 22:55:25 +0000
Subject: [PATCH 17/18] Update CHANGELOG.md

Co-Authored-By: johnno1962 <github@johnholdsworth.com>
---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3bf6d1ecc25e4..a6e816b46bdf0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,7 +25,7 @@ CHANGELOG
 Swift 5.1
 ---------
 
-* [SR-1340](https://bugs.swift.org/browse/SR-1340):
+* [SE-0068][]:
 
 `Self` can now be used inside member functions and for function arguments of structs and enums to refer to the containing type.
 

From a9312c6f97b03d96a9e95ddba0a84b5a8066ce37 Mon Sep 17 00:00:00 2001
From: John Holdsworth <github@johnholdsworth.com>
Date: Thu, 14 Mar 2019 23:13:40 +0000
Subject: [PATCH 18/18] Update CHANGELOG.md

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a6e816b46bdf0..2dd294a966f9e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -27,7 +27,7 @@ Swift 5.1
 
 * [SE-0068][]:
 
-`Self` can now be used inside member functions and for function arguments of structs and enums to refer to the containing type.
+  `Self` can now be used inside member functions and for function arguments of structs and enums to refer to the containing type.
 
 * [SR-7799][]: