Merge amethyst#1934

1934: Use World::get_mut with amethyst_derive r=azriel91 a=ishitatsuyuki ## Description A slight tweak to exploit `&mut World` to reduce runtime borrow checks. ## PR Checklist By placing an x in the boxes I certify that I have: - [X] Acknowledged that by making this pull request I release this code under an MIT/Apache 2.0 dual licensing scheme. If this modified or created any rs files: - [X] Ran `cargo +stable fmt --all` - [ ] Ran `cargo clippy --all --features "empty"` - [ ] Ran `cargo test --all --features "empty"` Co-authored-by: Tatsuyuki Ishi <[email protected]>
samgiles · Sep 21, 2019 · 3b91eab · 3b91eab
2 parents 56dd440 + 8bc4f6c
commit 3b91eab
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/amethyst_derive/src/system_desc.rs b/amethyst_derive/src/system_desc.rs
@@ -677,9 +677,14 @@ fn field_computation_expressions(system_desc_fields: &SystemDescFields<'_>) -> T
                         panic!("Expected `{}` field type to be `Type::Path`.", &field_name)
                     };
 
+                    let event_channel_error = format!(
+                        "Expected `EventChannel<{}>` to exist.",
+                        quote!(event_type_path).to_string()
+                    );
                     let tokens = quote! {
                         let #field_name = world
-                            .fetch_mut::<EventChannel<#event_type_path>>()
+                            .get_mut::<EventChannel<#event_type_path>>()
+                            .expect(#event_channel_error)
                             .register_reader();
                     };
                     token_stream.extend(tokens);