disable method overwrite warnings if both in Main

src/gf.c

@@ -974,15 +974,17 @@ static void method_overwrite(jl_typemap_entry_t *newentry, jl_method_t *oldvalue
     jl_module_t *newmod = method->module;
     jl_module_t *oldmod = oldvalue->module;
     JL_STREAM *s = JL_STDERR;
-    jl_printf(s, "WARNING: Method definition ");
-    jl_static_show_func_sig(s, (jl_value_t*)newentry->sig);
-    jl_printf(s, " in module %s", jl_symbol_name(oldmod->name));
-    print_func_loc(s, oldvalue);
-    jl_printf(s, " overwritten");
-    if (oldmod != newmod)
-        jl_printf(s, " in module %s", jl_symbol_name(newmod->name));
-    print_func_loc(s, method);
-    jl_printf(s, ".\n");
+    if (!(newmod == jl_main_module && oldmod == jl_main_module)) {
+        jl_printf(s, "WARNING: Method definition ");
+        jl_static_show_func_sig(s, (jl_value_t*)newentry->sig);
+        jl_printf(s, " in module %s", jl_symbol_name(oldmod->name));
+        print_func_loc(s, oldvalue);
+        jl_printf(s, " overwritten");
+        if (oldmod != newmod)
+            jl_printf(s, " in module %s", jl_symbol_name(newmod->name));
+        print_func_loc(s, method);
+        jl_printf(s, ".\n");
+    }
 }
 
 // invalidate cached methods that overlap this definition

test/compile.jl

@@ -366,4 +366,30 @@ let module_name = string("a",randstring())
     rm(file_name)
 end
 
+let
+    t = redirected_stderr("")
+    try
+        f_overwrite_main(x) = x
+        f_overwrite_main(x) = x
+    finally
+        close(STDERR)
+        redirect_stderr(olderr)
+    end
+    wait(t)
+
+    t = redirected_stderr("WARNING: Method definition f_overwrite_module(Any) in module F18725")
+    mktemp() do path, stream
+        try
+        include_string("""module F18725
+                f_overwrite_module(x) = x
+                f_overwrite_module(x) = x
+            end""")
+        finally
+            close(STDERR)
+            redirect_stderr(olderr)
+        end
+    end
+    wait(t)
+end
+
 end # !withenv