[RequirementMachine] Don't produced concrete type parameter diagnostics for

same-type requirements where one side is a parameter pack.

Author: hborla

lib/AST/RequirementMachine/RequirementMachineRequests.cpp

@@ -951,6 +951,13 @@ InferredGenericSignatureRequest::evaluate(
           continue;
 
         if (reduced->isTypeParameter()) {
+          // If one side is a parameter pack and the other is not, this is a
+          // same-element requirement that cannot be expressed with only one
+          // type parameter.
+          if ((genericParam->isParameterPack() && !reduced->isParameterPack()) ||
+              (!genericParam->isParameterPack() && reduced->isParameterPack()))
+            continue;
+
           ctx.Diags.diagnose(loc, diag::requires_generic_params_made_equal,
                              genericParam, result->getSugaredType(reduced))
             .warnUntilSwiftVersion(6);