fix #22164 and #22002, method sorting problems

fix #22164, specificity issue in ForwardDiff

(cherry picked from commit e92eb58)
partial backport of #22162

Author: JeffBezanson

src/subtype.c

@@ -2600,10 +2600,9 @@ 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/core.jl

@@ -98,6 +98,15 @@ _bound_vararg_specificity_1{T}(::Type{Array{T,1}}, d::Int) = 1
 @test args_morespecific(Tuple{Array}, Tuple{AbstractVector})
 @test args_morespecific(Tuple{Matrix}, Tuple{AbstractVector})
 
+# issue #22164 and #22002
+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
+
 # issue #12939
 module Issue12939
 abstract type Abs; end