Merge pull request swiftlang#6777 from slavapestov/fix-unqualified-lookup-rdar29961715

AST: Restore unqualified lookup quirk for Swift 3 mode

Author: slavapestov

lib/AST/NameLookup.cpp

@@ -649,13 +649,16 @@ UnqualifiedLookup::UnqualifiedLookup(DeclName Name, DeclContext *DC,
         ValueDecl *MetaBaseDecl = nullptr;
         GenericParamList *GenericParams = nullptr;
         Type ExtendedType;
-        
+        bool isTypeLookup = false;
+
         // If this declcontext is an initializer for a static property, then we're
         // implicitly doing a static lookup into the parent declcontext.
         if (auto *PBI = dyn_cast<PatternBindingInitializer>(DC))
           if (!DC->getParent()->isModuleScopeContext()) {
-            if (PBI->getBinding())
+            if (auto *PBD = PBI->getBinding()) {
+              isTypeLookup = PBD->isStatic();
               DC = DC->getParent();
+            }
           }
 
         if (auto *AFD = dyn_cast<AbstractFunctionDecl>(DC)) {
@@ -694,6 +697,10 @@ UnqualifiedLookup::UnqualifiedLookup(DeclName Name, DeclContext *DC,
                 ->getAsNominalTypeOrNominalTypeExtensionContext();
             DC = DC->getParent();
 
+            if (auto *FD = dyn_cast<FuncDecl>(AFD))
+              if (FD->isStatic())
+                isTypeLookup = true;
+
             // If we're not in the body of the function, the base declaration
             // is the nominal type, not 'self'.
             if (Loc.isValid() &&
@@ -780,6 +787,23 @@ UnqualifiedLookup::UnqualifiedLookup(DeclName Name, DeclContext *DC,
           DC->lookupQualified(ExtendedType, Name, options, TypeResolver, Lookup);
           bool FoundAny = false;
           for (auto Result : Lookup) {
+            // In Swift 3 mode, unqualified lookup skips static methods when
+            // performing lookup from instance context.
+            //
+            // We don't want to carry this forward to Swift 4, since it makes
+            // for poor diagnostics.
+            //
+            // Also, it was quite a special case and not as general as it
+            // should be -- it didn't apply to properties or subscripts, and
+            // the opposite case where we're in static context and an instance
+            // member shadows the module member wasn't handled either.
+            if (Ctx.isSwiftVersion3() &&
+                !isTypeLookup &&
+                isa<FuncDecl>(Result) &&
+                cast<FuncDecl>(Result)->isStatic()) {
+              continue;
+            }
+
             // Classify this declaration.
             FoundAny = true;
 

test/Compatibility/members.swift

@@ -0,0 +1,11 @@
+// RUN: %target-typecheck-verify-swift -swift-version 3
+
+struct X {
+  func f1(_ i: Int) { }
+  mutating func f1(_ f: Float) { }
+}
+
+func g0(_: (inout X) -> (Float) -> ()) {}
+
+// This becomes an error in Swift 4 mode -- probably a bug
+g0(X.f1)

test/Compatibility/unqualified_lookup.swift

@@ -0,0 +1,21 @@
+// RUN: %target-typecheck-verify-swift -swift-version 3
+
+// Stupid Swift 3 unqualified lookup quirk
+
+func f3(_ x: Int, _ y: Int, z: Int) { } // expected-note{{did you mean 'f3'?}}
+
+struct S0 {
+  func testS0() {
+    _ = f3(_:y:z:) // expected-error{{use of unresolved identifier 'f3(_:y:z:)'}}
+  }
+
+  static func f3(_ x: Int, y: Int, z: Int) -> S0 { return S0() }
+}
+
+extension Float {
+  func isClose(to: Float, epiValue: Float = 1e-5) -> Bool {
+    // Float.abs() and Swift.abs() are both visible here, but
+    // Swift 3 drops 'Float.abs()'.
+    return abs(self - to) < epiValue
+  }
+}

test/Constraints/members.swift

@@ -1,6 +1,4 @@
-// RUN: %target-typecheck-verify-swift
-
-import Swift
+// RUN: %target-typecheck-verify-swift -swift-version 4
 
 ////
 // Members of structs
@@ -9,9 +7,9 @@ import Swift
 struct X {
   func f0(_ i: Int) -> X { }
 
-  func f1(_ i: Int) { }
+  func f1(_ i: Int) { } // expected-note {{found this candidate}}
 
-  mutating func f1(_ f: Float) { }
+  mutating func f1(_ f: Float) { } // expected-note {{found this candidate}}
 
   func f2<T>(_ x: T) -> T { }
 }
@@ -29,7 +27,11 @@ func g0(_: (inout X) -> (Float) -> ()) {}
 
 _ = x.f0(i)
 x.f0(i).f1(i)
+
+// FIXME: Is this a bug in Swift 4 mode?
 g0(X.f1)
+// expected-error@-1 {{ambiguous reference to member 'f1'}}
+
 _ = x.f0(x.f2(1))
 _ = x.f0(1).f2(i)
 _ = yf.f0(1)

test/expr/primary/unqualified_name.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift
+// RUN: %target-typecheck-verify-swift -swift-version 4
 
 func f0(_ x: Int, y: Int, z: Int) { }
 func f1(_ x: Int, while: Int) { }

test/expr/unary/selector/property.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -disable-objc-attr-requires-foundation-module -typecheck -primary-file %s %S/Inputs/property_helper.swift -verify
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -disable-objc-attr-requires-foundation-module -typecheck -primary-file %s %S/Inputs/property_helper.swift -verify -swift-version 4
 import ObjectiveC
 
 // REQUIRES: objc_interop