[ConstraintSystem] Produce ambiguity notes based on the fix aggregate

It shouldn't matter how many fixes does the solution have overall,
what matter is how many fixes are there for the location in question.

Author: xedin

lib/Sema/ConstraintSystem.cpp

@@ -4674,10 +4674,16 @@ static bool diagnoseAmbiguity(
       auto noteLoc =
           decl->getLoc().isInvalid() ? getLoc(commonAnchor) : decl->getLoc();
 
-      if (solution.Fixes.size() == 1) {
-        diagnosed &=
-            solution.Fixes.front()->diagnose(solution, /*asNote*/ true);
-      } else if (llvm::all_of(solution.Fixes, [&](ConstraintFix *fix) {
+      SmallVector<const ConstraintFix *, 4> fixes;
+      for (const auto &entry : aggregateFix) {
+        if (entry.first == &solution)
+          fixes.push_back(entry.second);
+      }
+
+      if (fixes.size() == 1) {
+        diagnosed &= fixes.front()->diagnose(solution, /*asNote*/ true);
+      } else if (!fixes.empty() &&
+                 llvm::all_of(fixes, [&](const ConstraintFix *fix) {
                    return fix->getLocator()
                        ->findLast<LocatorPathElt::ApplyArgument>()
                        .has_value();
@@ -4691,8 +4697,7 @@ static bool diagnoseAmbiguity(
             type->lookThroughAllOptionalTypes()->getAs<AnyFunctionType>();
         assert(fn);
 
-        auto *argList =
-            solution.getArgumentList(solution.Fixes.front()->getLocator());
+        auto *argList = solution.getArgumentList(fixes.front()->getLocator());
         assert(argList);
 
         if (fn->getNumParams() == 1 && argList->isUnary()) {

test/Constraints/optional.swift

@@ -592,8 +592,8 @@ do {
 
 // Diagnose extraneous force unwrap in ambiguous context
 do {
-  func test(_: Int) {} // expected-note {{found this candidate}}
-  func test(_: String) {} // expected-note {{found this candidate}}
+  func test(_: Int) {} // expected-note {{candidate expects value of type 'Int' for parameter #1 (got 'Double')}}
+  func test(_: String) {} // expected-note {{candidate expects value of type 'String' for parameter #1 (got 'Double')}}
 
   var x: Double = 42
   test(x!) // expected-error {{no exact matches in call to local function 'test'}}

test/Generics/function_defs.swift

@@ -123,15 +123,15 @@ protocol Subscriptable {
   func getIndex() -> Index
   func getValue() -> Value
 
-  subscript (index : Index) -> Value { get set } // expected-note {{found this candidate}}
+  subscript (index : Index) -> Value { get set } // expected-note {{candidate expects value of type 'T.Index' for parameter #1 (got 'T.Value')}}
 }
 
 protocol IntSubscriptable {
   associatedtype ElementType
 
   func getElement() -> ElementType
 
-  subscript (index : Int) -> ElementType { get  } // expected-note {{found this candidate}}
+  subscript (index : Int) -> ElementType { get  } // expected-note {{candidate expects value of type 'Int' for parameter #1 (got 'T.Value')}}
 }
 
 func subscripting<T : Subscriptable & IntSubscriptable>(_ t: T) {

test/Sema/diag_ambiguous_overloads.swift

@@ -148,8 +148,8 @@ do {
   }
 }
 do {
-  func f1(_ u: Int) -> String {} // expected-note {{found this candidate}} expected-note {{candidate expects value of type 'Int' for parameter #1 (got 'Double')}}
-  func f1(_ u: String) -> Double {} // expected-note {{found this candidate}} expected-note {{candidate expects value of type 'String' for parameter #1 (got 'Double')}}
+  func f1(_ u: Int) -> String {} // expected-note 2 {{candidate expects value of type 'Int' for parameter #1 (got 'Double')}}
+  func f1(_ u: String) -> Double {} // expected-note 2 {{candidate expects value of type 'String' for parameter #1 (got 'Double')}}
   func f2(_ u: Int) {}
 
   f2(f1(1 as Double)) // expected-error {{no exact matches in call to local function 'f1'}}

test/expr/expressions.swift

@@ -749,7 +749,6 @@ func invalidDictionaryLiteral() {
 
 [4].joined(separator: [1])
 // expected-error@-1 {{no exact matches in call to instance method 'joined'}}
-// expected-note@-2 {{found candidate with type '(String) -> String'}}
 // There is one more note here - candidate requires that 'Int' conform to 'Sequence' (requirement specified as 'Self.Element' : 'Sequence') pointing to Sequence extension
 
 [4].joined(separator: [[[1]]])