[CS] Call checkParameterList for single-expr closures

Previously we would only call this in the delayed
application logic, which is currently run for
multi-statement closures. I'm planning on
removing that code path, which uncovered this
issue.

Author: hamishknight

lib/Sema/CSApply.cpp

@@ -8996,9 +8996,11 @@ namespace {
 
       switch (result) {
       case SolutionApplicationToFunctionResult::Success: {
-        if (auto closure = dyn_cast_or_null<ClosureExpr>(
-                fn.getAbstractClosureExpr()))
+        if (auto closure =
+                dyn_cast_or_null<ClosureExpr>(fn.getAbstractClosureExpr())) {
           TypeChecker::checkClosureAttributes(closure);
+          TypeChecker::checkParameterList(closure->getParameters(), closure);
+        }
         return false;
       }
 

test/attr/closures.swift

@@ -12,4 +12,13 @@ func testNonacceptedClosures() {
 
   _ = fn
   _ = fn2
+
+  // https://github.com/swiftlang/swift/issues/76291
+  _ = { (@objc x: Int) in 0 } // expected-error {{'@objc' attribute cannot be applied to this declaration}}
+  _ = { (@objc x: Int) in }  // expected-error {{'@objc' attribute cannot be applied to this declaration}}
+
+  _ = { (@objc x: Int) in  // expected-error {{'@objc' attribute cannot be applied to this declaration}}
+    print("hello")
+    return x
+  }
 }