AST: Restore old behavior for name lookup inside 'lazy' in Swift 3 mode

Restore the old Swift 3 behavior for source compatibility reasons:

- Unqualified lookup finds static properties (but not static methods)
  first, then global members.

- Qualified lookup into 'self' is still supported.

There's no change in Swift 4 mode, where the newer more correct
behavior is enabled.

Fixes <rdar://problem/32570766>.

Author: slavapestov

lib/AST/NameLookup.cpp

@@ -642,9 +642,12 @@ UnqualifiedLookup::UnqualifiedLookup(DeclName Name, DeclContext *DC,
 
             DC = DC->getParent();
 
-            BaseDecl = selfParam;
             ExtendedType = DC->getSelfTypeInContext();
             MetaBaseDecl = DC->getAsNominalTypeOrNominalTypeExtensionContext();
+            if (Ctx.isSwiftVersion3())
+              BaseDecl = MetaBaseDecl;
+            else
+              BaseDecl = selfParam;
 
             isTypeLookup = PBD->isStatic();
           }
@@ -705,7 +708,7 @@ UnqualifiedLookup::UnqualifiedLookup(DeclName Name, DeclContext *DC,
             // might be type checking a default argument expression and
             // performing name lookup from there), the base declaration
             // is the nominal type, not 'self'.
-            if (!AFD->isImplicit() &&
+            if ((Ctx.isSwiftVersion3() || !AFD->isImplicit()) &&
                 Loc.isValid() &&
                 AFD->getBodySourceRange().isValid() &&
                 !SM.rangeContainsTokenLoc(AFD->getBodySourceRange(), Loc)) {

test/Compatibility/lazy_properties.swift

@@ -0,0 +1,57 @@
+// RUN: %target-typecheck-verify-swift -parse-as-library -swift-version 3
+
+class ReferenceSelfInLazyProperty {
+  lazy var refs = (i, f())
+  // expected-error@-1 {{cannot use instance member 'i' within property initializer; property initializers run before 'self' is available}}
+  lazy var trefs: (Int, Int) = (i, f())
+  // expected-error@-1 {{instance member 'i' cannot be used on type 'ReferenceSelfInLazyProperty'}}
+
+  lazy var qrefs = (self.i, self.f())
+  lazy var qtrefs: (Int, Int) = (self.i, self.f())
+
+  lazy var crefs = { (i, f()) }()
+  // expected-error@-1 {{instance member 'i' cannot be used on type 'ReferenceSelfInLazyProperty'}}
+
+  lazy var ctrefs: (Int, Int) = { (i, f()) }()
+  // expected-error@-1 {{instance member 'i' cannot be used on type 'ReferenceSelfInLazyProperty'}}
+
+  lazy var cqrefs = { (self.i, self.f()) }()
+  lazy var cqtrefs: (Int, Int) = { (self.i, self.f()) }()
+
+  lazy var mrefs = { () -> (Int, Int) in return (i, f()) }()
+  // expected-error@-1 {{instance member 'i' cannot be used on type 'ReferenceSelfInLazyProperty'}}
+
+  lazy var mtrefs: (Int, Int) = { return (i, f()) }()
+  // expected-error@-1 {{instance member 'i' cannot be used on type 'ReferenceSelfInLazyProperty'}}
+
+  lazy var mqrefs = { () -> (Int, Int) in (self.i, self.f()) }()
+  lazy var mqtrefs: (Int, Int) = { return (self.i, self.f()) }()
+
+  lazy var lcqrefs = { [unowned self] in (self.i, self.f()) }()
+  lazy var lcqtrefs: (Int, Int) = { [unowned self] in (self.i, self.f()) }()
+
+  lazy var lmrefs = { [unowned self] () -> (Int, Int) in return (i, f()) }()
+  // expected-error@-1 {{instance member 'i' cannot be used on type 'ReferenceSelfInLazyProperty'}}
+  lazy var lmtrefs: (Int, Int) = { [unowned self] in return (i, f()) }()
+  // expected-error@-1 {{instance member 'i' cannot be used on type 'ReferenceSelfInLazyProperty'}}
+
+  lazy var lmqrefs = { [unowned self] () -> (Int, Int) in (self.i, self.f()) }()
+  lazy var lmqtrefs: (Int, Int) = { [unowned self] in return (self.i, self.f()) }()
+
+  var i = 42
+  func f() -> Int { return 0 }
+}
+
+class ReferenceStaticInLazyProperty {
+  lazy var refs1 = i
+  lazy var refs2 = f()
+  // expected-error@-1 {{use of unresolved identifier 'f'}}
+
+  lazy var trefs1: Int = i
+  lazy var trefs2: Int = f()
+  // expected-error@-1 {{use of unresolved identifier 'f'}}
+
+  static var i = 42
+  static func f() -> Int { return 0 }
+  // expected-note@-1 {{did you mean 'f'?}}
+}

test/NameBinding/name_lookup.swift

@@ -528,7 +528,7 @@ class r21677702 {
 // <rdar://problem/16954496> lazy properties must use "self." in their body, and can weirdly refer to class variables directly
 class r16954496 {
   func bar() {}
-  lazy var x: Array<() -> Void> = [bar]
+  lazy var x: Array<() -> Void> = [bar] // expected-error {{cannot convert value of type '(r16954496) -> () -> ()' to expected element type '() -> Void'}}
 }
 
 

test/SILGen/objc_properties.swift

@@ -242,7 +242,7 @@ class HasLazyProperty : NSObject, HasProperty {
     return nil
   }
 
-  lazy var window = instanceMethod()
+  lazy var window = self.instanceMethod()
 }
 
 // CHECK-LABEL: sil hidden @_T015objc_properties15HasLazyPropertyC6windowSo8NSObjectCSgfg : $@convention(method) (@guaranteed HasLazyProperty) -> @owned Optional<NSObject> {

test/decl/var/lazy_properties.swift

@@ -1,4 +1,3 @@
-// RUN: %target-typecheck-verify-swift -parse-as-library -swift-version 3
 // RUN: %target-typecheck-verify-swift -parse-as-library -swift-version 4
 
 lazy func lazy_func() {} // expected-error {{'lazy' may only be used on 'var' declarations}} {{1-6=}}
@@ -162,3 +161,19 @@ class ReferenceSelfInLazyProperty : BaseClass {
 
   lazy var refBaseClassProp = baseInstanceProp
 }
+
+class ReferenceStaticInLazyProperty {
+  lazy var refs1 = i
+  // expected-error@-1 {{static member 'i' cannot be used on instance of type 'ReferenceStaticInLazyProperty'}}
+  lazy var refs2 = f()
+  // expected-error@-1 {{static member 'f' cannot be used on instance of type 'ReferenceStaticInLazyProperty'}}
+
+  lazy var trefs1: Int = i
+  // expected-error@-1 {{static member 'i' cannot be used on instance of type 'ReferenceStaticInLazyProperty'}}
+
+  lazy var trefs2: Int = f()
+  // expected-error@-1 {{static member 'f' cannot be used on instance of type 'ReferenceStaticInLazyProperty'}}
+
+  static var i = 42
+  static func f() -> Int { return 0 }
+}