[Concurrency] Improve diagnostic for inout params with Sendable closures.

Error should point out any operation with mutable params is not permitted in a Sendable closure
Fixes rdar://89641516

Author: angela-laar

include/swift/AST/DiagnosticsSema.def

@@ -4566,6 +4566,10 @@ ERROR(concurrent_access_of_local_capture,none,
       "%select{mutation of|reference to}0 captured %1 %2 in "
       "concurrently-executing code",
       (bool, DescriptiveDeclKind, DeclName))
+ERROR(concurrent_access_of_inout_param,none,
+      "mutable capture of 'inout' parameter %0 is not allowed in "
+      "concurrently-executing code",
+      (DeclName))
 ERROR(non_sendable_capture,none,
       "capture of %1 with non-sendable type %0 in a `@Sendable` closure",
       (Type, DeclName))

lib/Sema/TypeCheckConcurrency.cpp

@@ -2553,6 +2553,13 @@ namespace {
           return false;
         }
 
+        if (auto param =  dyn_cast<ParamDecl>(value)){
+          if(param->isInOut()){
+              ctx.Diags.diagnose(loc, diag::concurrent_access_of_inout_param, param->getName());
+          }
+          return true;
+        }
+
         // Otherwise, we have concurrent access. Complain.
         ctx.Diags.diagnose(
             loc, diag::concurrent_access_of_local_capture,

test/Concurrency/async_tasks.swift

@@ -128,3 +128,12 @@ func test_detached_throwing() async -> String {
     print("caught: \(error)")
   }
 }
+
+// ==== Detached Tasks with inout Params---------------------------------------
+@available(SwiftStdlib 5.1, *)
+func printOrderNumber(n: inout Int) async {
+  Task.detached {
+      n+=1 //expected-error {{mutable capture of 'inout' parameter 'n' is not allowed in concurrently-executing code}}
+      print(n) //expected-error {{mutable capture of 'inout' parameter 'n' is not allowed in concurrently-executing code}}
+  }
+}