ModulePrinting: Using constraint solver to decide the right overload to print in synthesized extensions.

Author: nkcsgexi

lib/Sema/CSGen.cpp

@@ -3267,17 +3267,18 @@ swift::resolveValueMember(DeclContext &DC, Type BaseTy, DeclName Name) {
     ConstraintKind::ValueMember, Name, BaseTy, nullptr, false);
   if (LookupResult.ViableCandidates.empty())
     return Result;
-  if (OverloadChoice *Choice = LookupResult.getFavoredChoice()) {
-    Result.Favored = Choice->getDecl();
-  }
+  ConstraintLocator *Locator = CS.getConstraintLocator(nullptr);
+  TypeVariableType *TV = CS.createTypeVariable(Locator, TVO_CanBindToLValue);
+  CS.addOverloadSet(TV, LookupResult.ViableCandidates, Locator);
+  Optional<Solution> OpSolution = CS.solveSingle();
+  if (!OpSolution.hasValue())
+    return Result;
+  SelectedOverload Selected =  OpSolution.getValue().overloadChoices[Locator];
+  Result.Favored = Selected.choice.getDecl();
   for (OverloadChoice& Choice : LookupResult.ViableCandidates) {
     ValueDecl *VD = Choice.getDecl();
     if (VD != Result.Favored)
       Result.OtherViables.push_back(VD);
   }
-  if (!Result.Favored) {
-    Result.Favored = Result.OtherViables.front();
-    Result.OtherViables.erase(Result.OtherViables.begin());
-  }
   return Result;
 }

test/IDE/print_synthesized_extensions.swift

@@ -173,6 +173,31 @@ public extension P5 {
  public func foo2() {}
 }
 
+public extension P5 {
+
+  /// This is not picked
+  public func foo3() {}
+}
+
+public extension P5 where T1 : Comparable{
+
+  /// This is picked
+  public func foo3() {}
+}
+
+public extension P5  where T1 : Comparable {
+
+  /// This is picked
+  public func foo4() {}
+}
+
+public extension P5 {
+
+  /// This is not picked
+  public func foo4() {}
+}
+
+
 public struct S12 : P5{
   public typealias T1 = Int
   public func foo1() {}
@@ -240,10 +265,14 @@ public struct S12 : P5{
 // CHECK10-NEXT:     <decl:Func>public func <loc>ef5(<decl:Param>t: <ref:Struct>S5</ref></decl>)</loc></decl>
 // CHECK10-NEXT: }</synthesized>
 
-// CHECK11: <decl:Struct>public struct <loc>S12</loc> : <ref:Protocol>P5</ref> {
-// CHECK11-NEXT: <decl:TypeAlias>public typealias <loc>T1</loc> = <ref:Struct>Int</ref></decl>
-// CHECK11-NEXT: <decl:Func>/// This is picked
-// CHECK11-NEXT: public func <loc>foo1()</loc></decl></decl>
-// CHECK11-NEXT: <decl:Func>/// This is picked
-// CHECK11-NEXT: public func <loc>foo2()</loc></decl>
+// CHECK11:      <decl:Struct>public struct <loc>S12</loc> : <ref:Protocol>P5</ref> {
+// CHECK11-NEXT:  <decl:TypeAlias>public typealias <loc>T1</loc> = <ref:Struct>Int</ref></decl>
+// CHECK11-NEXT:  <decl:Func>/// This is picked
+// CHECK11-NEXT:    public func <loc>foo1()</loc></decl></decl>
+// CHECK11-NEXT:  <decl:Func>/// This is picked
+// CHECK11-NEXT:    public func <loc>foo2()</loc></decl>
+// CHECK11-NEXT:  <decl:Func>/// This is picked
+// CHECK11-NEXT:    public func <loc>foo3()</loc></decl>
+// CHECK11-NEXT:  <decl:Func>/// This is picked
+// CHECK11-NEXT:    public func <loc>foo4()</loc></decl>
 // CHECK11-NEXT: }</synthesized>