fix #29429, make local-sparam conflict an error instead of warning

NEWS.md

@@ -16,6 +16,8 @@ Language changes
   * Big integer literals and command syntax (backticks) are now parsed with the name of
     the macro (`@int128_str`, `@uint128_str`, `@big_str`, `@cmd`) qualified to refer
     to the `Core` module ([#29968]).
+  * Using the same name for both a local variable and a static parameter is now an error instead
+    of a warning ([#29429]).
 
 New library functions
 ---------------------

src/julia-syntax.scm

@@ -2513,6 +2513,11 @@
                                  (if (memq v argnames)
                                      (error (string "local variable name \"" v "\" conflicts with an argument"))))
                                locals-declared)))
+               (if (and (pair? sp) (eq? e (lam:body lam)))
+                   (for-each (lambda (v)
+                               (if (memq v all-vars)
+                                   (error (string "local variable name \"" v "\" conflicts with a static parameter"))))
+                             sp))
                (if lam ;; update in-place the list of local variables in lam
                    (set-car! (cddr lam)
                              (append real-new-vars real-new-vars-def (caddr lam))))

src/method.c

@@ -640,29 +640,6 @@ static jl_method_t *jl_new_method(
 
 void print_func_loc(JL_STREAM *s, jl_method_t *m);
 
-static void jl_check_static_parameter_conflicts(jl_method_t *m, jl_code_info_t *src, jl_svec_t *t)
-{
-    size_t nvars = jl_array_len(src->slotnames);
-
-    size_t i, n = jl_svec_len(t);
-    for (i = 0; i < n; i++) {
-        jl_value_t *tv = jl_svecref(t, i);
-        size_t j;
-        for (j = 0; j < nvars; j++) {
-            if (jl_is_typevar(tv)) {
-                if ((jl_sym_t*)jl_array_ptr_ref(src->slotnames, j) == ((jl_tvar_t*)tv)->name) {
-                    jl_printf(JL_STDERR,
-                              "WARNING: local variable %s conflicts with a static parameter in %s",
-                              jl_symbol_name(((jl_tvar_t*)tv)->name),
-                              jl_symbol_name(m->name));
-                    print_func_loc(JL_STDERR, m);
-                    jl_printf(JL_STDERR, ".\n");
-                }
-            }
-        }
-    }
-}
-
 // empty generic function def
 JL_DLLEXPORT jl_value_t *jl_generic_function_def(jl_sym_t *name,
                                                  jl_module_t *module,
@@ -818,7 +795,6 @@ JL_DLLEXPORT void jl_method_def(jl_svec_t *argdata,
                           m->line);
     }
 
-    jl_check_static_parameter_conflicts(m, f, tvars);
     jl_method_table_insert(mt, m, NULL);
     if (jl_newmeth_tracer)
         jl_call_tracer(jl_newmeth_tracer, (jl_value_t*)m);

test/syntax.jl

@@ -1556,21 +1556,13 @@ end
 end
 @test A27807.@m()(1,1.0) === (1, 0.0)
 
-# issue #27896
-let oldstderr = stderr, newstderr, errtxt
-    try
-        newstderr = redirect_stderr()
-        @eval function foo(a::A, b::B) where {A,B}
-            B = eltype(A)
-            return convert(B, b)
-        end
-        errtxt = @async read(newstderr[1], String)
-    finally
-        redirect_stderr(oldstderr)
-        close(newstderr[2])
+# issue #27896 / #29429
+@test Meta.lower(@__MODULE__, quote
+    function foo(a::A, b::B) where {A,B}
+        B = eltype(A)
+        return convert(B, b)
     end
-    @test occursin("WARNING: local variable B conflicts with a static parameter", fetch(errtxt))
-end
+end) == Expr(:error, "local variable name \"B\" conflicts with a static parameter")
 
 # issue #28044
 code28044(x) = 10x