[ConstraintSystem] Don't increase a score for conditional requirement failures

Let's consider conditional requirement failure to mean that parent
conformance requirement wasn't satisfied and nothing more, that helps
to disambiguate certain situations and avoid filtering out conditional
failures.

Resolves: rdar://problem/64844584

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -1672,20 +1672,6 @@ assessRequirementFailureImpact(ConstraintSystem &cs, Type requirementType,
   if (!anchor)
     return impact;
 
-  // If this is a conditional requirement failure associated with a
-  // call, let's increase impact of the fix to show that such failure
-  // makes member/function unreachable in current context or with
-  // given arguments.
-  if (auto last = locator.last()) {
-    if (last->isConditionalRequirement()) {
-      if (auto *expr = getAsExpr(anchor)) {
-        auto *parent = cs.getParentExpr(expr);
-        if (parent && isa<ApplyExpr>(parent))
-          return 5;
-      }
-    }
-  }
-
   // If this requirement is associated with a member reference and it
   // was possible to check it before overload choice is bound, that means
   // types came from the context (most likely Self, or associated type(s))

test/Constraints/bridging.swift

@@ -180,7 +180,8 @@ func dictionaryToNSDictionary() {
 // In this case, we should not implicitly convert Dictionary to NSDictionary.
 struct NotEquatable {}
 func notEquatableError(_ d: Dictionary<Int, NotEquatable>) -> Bool {
-  return d == d // expected-error{{referencing operator function '==' on 'Dictionary' requires that 'NotEquatable' conform to 'Equatable'}}
+  // There is a note attached to a requirement `requirement from conditional conformance of 'Dictionary<Int, NotEquatable>' to 'Equatable'`
+  return d == d // expected-error{{operator function '==' requires that 'NotEquatable' conform to 'Equatable'}}
 }
 
 // NSString -> String

test/Constraints/operator.swift

@@ -216,14 +216,11 @@ func rdar46459603() {
   let e = E.foo(value: "String")
   var arr = ["key": e]
 
-  // FIXME(rdar://problem/64844584) - on iOS simulator this diagnostic is flaky,
-  // either `referencing operator function '==' on 'Equatable'` or `operator function '==' requires`
   _ = arr.values == [e]
-  // expected-error@-1 {{requires that 'Dictionary<String, E>.Values' conform to 'Equatable'}}
-  // expected-error@-2 {{cannot convert value of type '[E]' to expected argument type 'Dictionary<String, E>.Values'}}
+  // expected-error@-1 {{binary operator '==' cannot be applied to operands of type 'Dictionary<String, E>.Values' and '[E]'}}
   _ = [arr.values] == [[e]]
-  // expected-error@-1 {{requires that 'Dictionary<String, E>.Values' conform to 'Equatable'}}
-  // expected-error@-2 {{cannot convert value of type '[E]' to expected element type 'Dictionary<String, E>.Values'}}
+  // expected-error@-1 {{referencing operator function '==' on 'Array' requires that 'E' conform to 'Equatable'}} expected-note@-1 {{binary operator '==' cannot be synthesized for enums with associated values}}
+  // expected-error@-2 {{cannot convert value of type 'Dictionary<String, E>.Values' to expected element type '[E]'}}
 }
 
 // SR-10843

test/Generics/conditional_conformances.swift

@@ -413,9 +413,9 @@ extension Foo: P where Bar: P {
 extension BinaryInteger {
   var foo: Self {
     return self <= 1
-            ? 1 // expected-error {{cannot convert return expression of type 'Int' to return type 'Self'}}
+            ? 1
             : (2...self).reduce(1, *)
-            // expected-error@-1 {{cannot convert value of type 'Self' to expected argument type 'Int'}} {{20-20=Int(}} {{24-24=)}}
+            // expected-error@-1 {{referencing instance method 'reduce' on 'ClosedRange' requires that 'Self.Stride' conform to 'SignedInteger'}}
   }
 }
 

test/Parse/pointer_conversion.swift.gyb

@@ -307,7 +307,8 @@ struct NotEquatable {}
 func arrayComparison(_ x: [NotEquatable], y: [NotEquatable], p: UnsafeMutablePointer<NotEquatable>) {
   var x = x
   // Don't allow implicit array-to-pointer conversions in operators.
-  let a: Bool = x == y // expected-error{{referencing operator function '==' on 'Array' requires that 'NotEquatable' conform to 'Equatable'}}
+  // There is a note attached to declaration - requirement from conditional conformance of '[NotEquatable]' to 'Equatable'
+  let a: Bool = x == y // expected-error{{operator function '==' requires that 'NotEquatable' conform to 'Equatable'}}
   let _: Bool = p == &x  // Allowed!
 }
 

test/expr/unary/keypath/salvage-with-other-type-errors.swift

@@ -53,8 +53,9 @@ protocol Bindable: class { }
 
 extension Bindable {
   func test<Value>(to targetKeyPath: ReferenceWritableKeyPath<Self, Value>, change: Value?) {
+    // There is also a note attached to declaration - requirement from conditional conformance of 'Optional<Value>' to 'Equatable'
     if self[keyPath:targetKeyPath] != change {
-      // expected-error@-1 {{binary operator '!=' cannot be applied to operands of type 'Value' and 'Value?'}}
+      // expected-error@-1 {{operator function '!=' requires that 'Value' conform to 'Equatable'}}
       self[keyPath: targetKeyPath] = change!
     }
   }

test/stdlib/ArrayDiagnostics.swift

@@ -4,5 +4,6 @@ class NotEquatable {}
 
 func test_ArrayOfNotEquatableIsNotEquatable() {
   var a = [ NotEquatable(), NotEquatable() ]
-  if a == a {} // expected-error {{referencing operator function '==' on 'Array' requires that 'NotEquatable' conform to 'Equatable'}}
+  // There is also a note attached to declaration - requirement from conditional conformance of '[NotEquatable]' to 'Equatable'
+  if a == a {} // expected-error {{operator function '==' requires that 'NotEquatable' conform to 'Equatable'}}
 }