[CSFix] Fix getConcurrencyFixBehavior to account for non-decl overloads

Adjust the downgrade check for static member references to
account for the fact that argument could come of a tuple or
some other reference that doesn't have a declaration associated
with it.

Resolves: rdar://153083848

Author: xedin

lib/Sema/CSFix.cpp

@@ -300,7 +300,7 @@ getConcurrencyFixBehavior(ConstraintSystem &cs, ConstraintKind constraintKind,
       if (auto *argument = getAsExpr(simplifyLocatorToAnchor(argLoc))) {
         if (auto overload = cs.findSelectedOverloadFor(
                 argument->getSemanticsProvidingExpr())) {
-          auto *decl = overload->choice.getDecl();
+          auto *decl = overload->choice.getDeclOrNull();
           if (decl && decl->isStatic())
             return FixBehavior::DowngradeToWarning;
         }

test/Concurrency/sendable_checking.swift

@@ -526,3 +526,11 @@ func sendablePacks<each Element: Sendable>(
 
 @available(SwiftStdlib 5.1, *)
 func sendPack<each Element>(_: repeat each Element) async {}
+
+// rdar://153083848 - crash in `getConcurrencyFixBehavior` when member comes from a tuple
+func test(value: (_: Int, _: () -> Void)) {
+  func takesSendable(_: @Sendable () -> Void) {}
+
+  takesSendable(value.1) // Ok
+  // expected-warning@-1 {{converting non-Sendable function value to '@Sendable () -> Void' may introduce data races}}
+}