remove warning from c when binding is ambiguous

Author: IanButterworth

doc/src/manual/modules.md

@@ -283,14 +283,14 @@ julia> module B
 B
 ```
 
-The statement `using .A, .B` works, but when you try to call `f`, you get a warning
+The statement `using .A, .B` works, but when you try to call `f`, you get an error with a hint
 
 ```jldoctest module_manual
 julia> using .A, .B
 
 julia> f
-WARNING: both B and A export "f"; uses of it in module Main must be qualified
 ERROR: UndefVarError: `f` not defined in `Main`
+Hint: It looks like two or more modules export different bindings with this name, resulting in ambiguity. Try explicitly importing it from a particular module, or qualifying the name with the module it should come from.
 ```
 
 Here, Julia cannot decide which `f` you are referring to, so you have to make a choice. The following solutions are commonly used:

src/module.c

@@ -423,21 +423,8 @@ static jl_binding_t *using_resolve_binding(jl_module_t *m JL_PROPAGATES_ROOT, jl
             jl_ptr_kind_union_t tempb_pku = jl_atomic_load_relaxed(&tempbpart->restriction);
             assert(decode_restriction_kind(tempb_pku) == BINDING_KIND_GLOBAL || decode_restriction_kind(tempb_pku) == BINDING_KIND_DECLARED || jl_bkind_is_some_constant(decode_restriction_kind(tempb_pku)));
             (void)tempb_pku;
-            if (bpart != NULL && !tempb->deprecated && !b->deprecated && !eq_bindings(tempbpart, b, jl_current_task->world_age)) {
-                if (warn) {
-                    // set usingfailed=1 to avoid repeating this warning
-                    // the owner will still be NULL, so it can be later imported or defined
-                    tempb = jl_get_module_binding(m, var, 1);
-                    tempbpart = jl_get_binding_partition(tempb, jl_current_task->world_age);
-                    jl_atomic_store_release(&tempbpart->restriction, encode_restriction(NULL, BINDING_KIND_FAILED));
-                    jl_printf(JL_STDERR,
-                              "WARNING: both %s and %s export \"%s\"; uses of it in module %s must be qualified\n",
-                              jl_symbol_name(owner->name),
-                              jl_symbol_name(imp->name), jl_symbol_name(var),
-                              jl_symbol_name(m->name));
-                }
+            if (bpart != NULL && !tempb->deprecated && !b->deprecated && !eq_bindings(tempbpart, b, jl_current_task->world_age))
                 return NULL;
-            }
             if (owner == NULL || !tempb->deprecated) {
                 owner = imp;
                 b = tempb;