[CSDiagnostics] Update shouldHaveDirectCalleeOverload

Given we can now find overloads for applies of optional functions,
adjust the logic so we look at the call's direct callee. In addition,
tweak the logic so we don't assert on a ForceTryExpr.

Author: hamishknight

lib/Sema/CSDiagnostics.cpp

@@ -158,8 +158,8 @@ Type FailureDiagnostic::resolveInterfaceType(Type type,
 
 /// Given an apply expr, returns true if it is expected to have a direct callee
 /// overload, resolvable using `getChoiceFor`. Otherwise, returns false.
-static bool shouldHaveDirectCalleeOverload(const ApplyExpr *apply) {
-  auto *fnExpr = apply->getFn()->getValueProvidingExpr();
+static bool shouldHaveDirectCalleeOverload(const CallExpr *callExpr) {
+  auto *fnExpr = callExpr->getDirectCallee();
 
   // An apply of an apply/subscript doesn't have a direct callee.
   if (isa<ApplyExpr>(fnExpr) || isa<SubscriptExpr>(fnExpr))
@@ -169,11 +169,9 @@ static bool shouldHaveDirectCalleeOverload(const ApplyExpr *apply) {
   if (isa<ClosureExpr>(fnExpr))
     return false;
 
-  // If the optionality changes, there's no direct callee.
-  if (isa<BindOptionalExpr>(fnExpr) || isa<ForceValueExpr>(fnExpr) ||
-      isa<OptionalTryExpr>(fnExpr)) {
+  // No direct callee for a try!/try?.
+  if (isa<ForceTryExpr>(fnExpr) || isa<OptionalTryExpr>(fnExpr))
     return false;
-  }
 
   // If we have an intermediate cast, there's no direct callee.
   if (isa<ExplicitCastExpr>(fnExpr))

test/Constraints/function.swift

@@ -169,7 +169,7 @@ func returnsTakesEscapingFn() -> (@escaping () -> Int) -> Void { takesEscapingFn
 prefix operator ^^^
 prefix func ^^^(_ x: Int) -> (@escaping () -> Int) -> Void { takesEscapingFn }
 
-func testWeirdFnExprs<T>(_ fn: () -> Int, _ cond: Bool, _ any: Any, genericArg: T) { // expected-note 11{{parameter 'fn' is implicitly non-escaping}}
+func testWeirdFnExprs<T>(_ fn: () -> Int, _ cond: Bool, _ any: Any, genericArg: T) { // expected-note 12{{parameter 'fn' is implicitly non-escaping}}
   (any as! (@escaping () -> Int) -> Void)(fn)
   // expected-error@-1 {{passing non-escaping parameter 'fn' to function expecting an @escaping closure}}
 
@@ -183,6 +183,9 @@ func testWeirdFnExprs<T>(_ fn: () -> Int, _ cond: Bool, _ any: Any, genericArg:
   (^^^5)(fn)
   // expected-error@-1 {{passing non-escaping parameter 'fn' to function expecting an @escaping closure}}
 
+  (try! takesEscapingFn)(fn)
+  // expected-error@-1 {{passing non-escaping parameter 'fn' to function expecting an @escaping closure}}
+
   var optFn: Optional = takesEscapingFn
   optFn?(fn)
   // expected-error@-1 {{passing non-escaping parameter 'fn' to function expecting an @escaping closure}}