describe noncopyables in parameter packs

Author: kavon

include/swift/AST/DiagnosticsSema.def

@@ -7221,6 +7221,9 @@ ERROR(noncopyable_generics_generic_param_metatype, none,
 NOTE(noncopyable_generics_implicit_copyable, none,
       "%0 %1 has an implicit Copyable requirement",
       (DescriptiveDeclKind, Type))
+ERROR(noncopyable_element_of_pack_not_supported,none,
+      "parameter pack containing noncopyable element %0 is not supported",
+      (Type))
 ERROR(noncopyable_effectful_getter,none,
       "%0 of noncopyable type cannot be 'async' or 'throws'", (DescriptiveDeclKind))
 ERROR(noncopyable_enums_do_not_support_indirect,none,

lib/Sema/CSDiagnostics.cpp

@@ -6118,6 +6118,12 @@ bool NotCopyableFailure::diagnoseAsError() {
       return true;
     }
 
+    if (loc->isLastElement<LocatorPathElt::PackElement>()) {
+      emitDiagnostic(diag::noncopyable_element_of_pack_not_supported,
+                     noncopyableTy);
+      return true;
+    }
+
     // a bit paranoid of nulls and such...
     if (auto *genericParam = loc->getGenericParameter()) {
       if (auto *paramDecl = genericParam->getDecl()) {

test/Constraints/moveonly_constraints.swift

@@ -289,5 +289,5 @@ func tryToDoBadMetatypeStuff() {
 
 func packingHeat<each T>(_ t: repeat each T) {}
 func packIt() {
-  packingHeat(MO())  // expected-error {{noncopyable type 'MO' cannot be used with generics yet}}
+  packingHeat(MO())  // expected-error {{parameter pack containing noncopyable element 'MO' is not supported}}
 }