[Concurrency] Check function conversions after their sub-expressions have been checked

Explicit closure expressions gets their isolation inferred during
actor isolation checking, if they appear as a sub-expression to
a function conversion we need to delay function checking until
the closure was processed. It shouldn't matter for other cases.

(cherry picked from commit 61fbaa7)

Author: xedin

lib/Sema/TypeCheckConcurrency.cpp

@@ -3477,19 +3477,6 @@ namespace {
         }
       }
 
-      // The constraint solver may not have chosen legal casts.
-      if (auto funcConv = dyn_cast<FunctionConversionExpr>(expr)) {
-        checkFunctionConversion(funcConv,
-                                funcConv->getSubExpr()->getType(),
-                                funcConv->getType());
-      }
-
-      if (auto *isolationErasure = dyn_cast<ActorIsolationErasureExpr>(expr)) {
-        checkFunctionConversion(isolationErasure,
-                                isolationErasure->getSubExpr()->getType(),
-                                isolationErasure->getType());
-      }
-
       if (auto *defaultArg = dyn_cast<DefaultArgumentExpr>(expr)) {
         checkDefaultArgument(defaultArg);
       }
@@ -3581,6 +3568,19 @@ namespace {
         }
       }
 
+      // The constraint solver may not have chosen legal casts.
+      if (auto funcConv = dyn_cast<FunctionConversionExpr>(expr)) {
+        checkFunctionConversion(funcConv,
+                                funcConv->getSubExpr()->getType(),
+                                funcConv->getType());
+      }
+
+      if (auto *isolationErasure = dyn_cast<ActorIsolationErasureExpr>(expr)) {
+        checkFunctionConversion(isolationErasure,
+                                isolationErasure->getSubExpr()->getType(),
+                                isolationErasure->getType());
+      }
+
       return Action::Continue(expr);
     }