fix #22164, specificity issue in ForwardDiff

Author: JeffBezanson

src/subtype.c

@@ -2576,10 +2576,9 @@ static int type_morespecific_(jl_value_t *a, jl_value_t *b, int invariant, jl_ty
         if (!jl_is_type(b))
             return 0;
         if (invariant) {
-            if (num_occurs((jl_tvar_t*)a, env) < 2)
-                return 0;
             if (eq_msp(((jl_tvar_t*)a)->ub, b, env))
-                return 1;
+                return num_occurs((jl_tvar_t*)a, env) >= 2;
+            return 0;
         }
         return type_morespecific_((jl_value_t*)((jl_tvar_t*)a)->ub, b, 0, env);
     }

test/specificity.jl

@@ -142,3 +142,12 @@ f17016(f, t1::Tuple) = 1
 
 @test args_morespecific(Tuple{Type{CartesianIndex{N}}} where N,
                         Tuple{Type{CartesianIndex{N}},Vararg{Int,N}} where N)
+
+# issue #22164
+let A = Tuple{Type{D},D} where D<:Pair,
+    B = Tuple{Type{Any}, Any},
+    C = Tuple{Type{Pair}, Pair}
+    @test  args_morespecific(C, A)
+    @test !args_morespecific(A, B)
+    @test !args_morespecific(C, B)
+end