refine method overwrite warning

Always show the warning for anonymous functions, but update the verbiage
to give additional information. This warning can still be avoided by
explicitly calling delete_method first.

fixes #32635
fixes #35140
refs #15602

src/datatype.c

@@ -521,10 +521,10 @@ void jl_compute_field_offsets(jl_datatype_t *st)
 
 static int is_anonfn_typename(char *name)
 {
-    if (name[0] != '#')
+    if (name[0] != '#' || name[1] == '#')
         return 0;
     char *other = strrchr(name, '#');
-    return (name[1] != '#' && other > &name[1] && is10digit(other[1]));
+    return other > &name[1] && is10digit(other[1]);
 }
 
 JL_DLLEXPORT jl_datatype_t *jl_new_datatype(

src/dump.c

@@ -2341,8 +2341,7 @@ static void jl_recache_types(void) JL_GC_DISABLED
     }
 }
 
-// repeatedly look up older methods until we come to one that existed
-// at the time this module was serialized (e.g. ignoring deletion)
+// look up a method from a previously deserialized dependent module
 static jl_method_t *jl_lookup_method(jl_methtable_t *mt, jl_datatype_t *sig, size_t world)
 {
     if (world < jl_main_module->primary_world)

src/gf.c

@@ -1197,15 +1197,6 @@ static jl_method_instance_t *jl_mt_assoc_by_type(jl_methtable_t *mt, jl_datatype
     return nf;
 }
 
-void print_func_loc(JL_STREAM *s, jl_method_t *m)
-{
-    long lno = m->line;
-    if (lno > 0) {
-        char *fname = jl_symbol_name((jl_sym_t*)m->file);
-        jl_printf(s, " at %s:%ld", fname, lno);
-    }
-}
-
 struct shadowed_matches_env {
     struct typemap_intersection_env match;
     jl_typemap_entry_t *newentry;
@@ -1291,14 +1282,33 @@ static jl_value_t *check_shadowed_matches(jl_typemap_t *defs, jl_typemap_entry_t
     return env.shadowed;
 }
 
+void print_func_loc(JL_STREAM *s, jl_method_t *m)
+{
+    long lno = m->line;
+    if (lno > 0) {
+        char *fname = jl_symbol_name((jl_sym_t*)m->file);
+        jl_printf(s, " at %s:%ld", fname, lno);
+    }
+}
+
+static int is_anonfn_typename(char *name)
+{
+    if (name[0] != '#' || name[1] == '#')
+        return 0;
+    char *other = strrchr(name, '#');
+    return other > &name[1] && other[1] > '0' && other[1] <= '9';
+}
+
 static void method_overwrite(jl_typemap_entry_t *newentry, jl_method_t *oldvalue)
 {
     // method overwritten
+    jl_method_t *method = (jl_method_t*)newentry->func.method;
+    jl_module_t *newmod = method->module;
+    jl_module_t *oldmod = oldvalue->module;
+    jl_datatype_t *dt = jl_first_argument_datatype(oldvalue->sig);
+    int anon = dt && is_anonfn_typename(jl_symbol_name(dt->name->name));
     if ((jl_options.warn_overwrite == JL_OPTIONS_WARN_OVERWRITE_ON) ||
-        (jl_options.incremental && jl_generating_output())) {
-        jl_method_t *method = (jl_method_t*)newentry->func.method;
-        jl_module_t *newmod = method->module;
-        jl_module_t *oldmod = oldvalue->module;
+        (jl_options.incremental && jl_generating_output()) || anon) {
         JL_STREAM *s = JL_STDERR;
         jl_printf(s, "WARNING: Method definition ");
         jl_static_show_func_sig(s, (jl_value_t*)newentry->sig);
@@ -1307,7 +1317,10 @@ static void method_overwrite(jl_typemap_entry_t *newentry, jl_method_t *oldvalue
         jl_printf(s, " overwritten");
         if (oldmod != newmod)
             jl_printf(s, " in module %s", jl_symbol_name(newmod->name));
-        print_func_loc(s, method);
+        if (method->line > 0 && method->line == oldvalue->line && method->file == oldvalue->file)
+            jl_printf(s, anon ? " on the same line" : " on the same line (check for duplicate calls to `include`)");
+        else
+            print_func_loc(s, method);
         jl_printf(s, ".\n");
         jl_uv_flush(s);
     }

test/misc.jl

@@ -78,13 +78,25 @@ end
 @test GC.enable(true)
 
 # PR #10984
-# Disable on windows because of issue (missing flush) when redirecting stderr.
 let
     redir_err = "redirect_stderr(stdout)"
     exename = Base.julia_cmd()
-    script = "$redir_err; module A; f() = 1; end; A.f() = 1"
+    script = """
+        $redir_err
+        module A; f() = 1; end; A.f() = 1
+        A.f() = 1
+        outer() = (g() = 1; g() = 2; g)
+        """
     warning_str = read(`$exename --warn-overwrite=yes --startup-file=no -e $script`, String)
-    @test occursin("f()", warning_str)
+    @test warning_str == """
+        WARNING: Method definition f() in module A at none:2 overwritten in module Main on the same line (check for duplicate calls to `include`).
+        WARNING: Method definition f() in module Main at none:2 overwritten at none:3.
+        WARNING: Method definition g() in module Main at none:4 overwritten on the same line.
+        """
+    warning_str = read(`$exename --startup-file=no -e $script`, String)
+    @test warning_str == """
+        WARNING: Method definition g() in module Main at none:4 overwritten on the same line.
+        """
 end
 
 # lock / unlock