allow nested combinations of (named)tuples, symbols, and bits as type…

… parameters

src/builtins.c

@@ -1258,20 +1258,28 @@ JL_CALLABLE(jl_f_set_binding_type)
 
 // apply_type -----------------------------------------------------------------
 
-int jl_valid_type_param(jl_value_t *v)
+static int is_nestable_type_param(jl_value_t *t)
 {
-    if (jl_is_tuple(v)) {
+    if (jl_is_namedtuple_type(t))
+        t = jl_tparam1(t);
+    if (jl_is_tuple_type(t)) {
         // NOTE: tuples of symbols are not currently bits types, but have been
         // allowed as type parameters. this is a bit ugly.
-        jl_value_t *tt = jl_typeof(v);
-        size_t i, l = jl_nparams(tt);
-        for(i=0; i < l; i++) {
-            jl_value_t *pi = jl_tparam(tt,i);
-            if (!(pi == (jl_value_t*)jl_symbol_type || jl_isbits(pi)))
+        size_t i, l = jl_nparams(t);
+        for (i = 0; i < l; i++) {
+            jl_value_t *pi = jl_tparam(t, i);
+            if (!(pi == (jl_value_t*)jl_symbol_type || jl_isbits(pi) || is_nestable_type_param(pi)))
                 return 0;
         }
         return 1;
     }
+    return 0;
+}
+
+int jl_valid_type_param(jl_value_t *v)
+{
+    if (jl_is_tuple(v) || jl_is_namedtuple(v))
+        return is_nestable_type_param(jl_typeof(v));
     if (jl_is_vararg(v))
         return 0;
     // TODO: maybe more things

test/core.jl

@@ -1987,9 +1987,8 @@ mutable struct TupleParam{P}
     x::Bool
 end
 
-function tupledispatch(a::TupleParam{(1,:a)})
-    a.x
-end
+tupledispatch(a::TupleParam{(1,:a)}) = a.x
+tupledispatch(a::TupleParam{(1,(:a,))}) = 42
 
 # tuples can be used as type params
 let t1 = TupleParam{(1,:a)}(true),
@@ -2001,6 +2000,10 @@ let t1 = TupleParam{(1,:a)}(true),
     # dispatch works properly
     @test tupledispatch(t1) == true
     @test_throws MethodError tupledispatch(t2)
+
+    @test tupledispatch(TupleParam{(1,(:a,))}(true)) === 42
+    @test_throws TypeError TupleParam{NamedTuple{(:a,), Tuple{Any}}((1,))}
+    @test_throws TypeError Val{NamedTuple{(:a,), Tuple{NamedTuple{<:Any,Tuple{Int}}}}(((x=2,),))}
 end
 
 # issue #5254