Implement GString concatenation operator

godot-core/src/builtin/string/gstring.rs

@@ -8,15 +8,18 @@
 use std::convert::Infallible;
 use std::fmt;
 use std::fmt::Write;
+use std::ops::Add;
 
 use godot_ffi as sys;
 use sys::types::OpaqueString;
 use sys::{ffi_methods, interface_fn, GodotFfi};
 
 use crate::builtin::string::Encoding;
 use crate::builtin::{inner, NodePath, StringName, Variant};
+use crate::global::str;
 use crate::meta::error::StringError;
 use crate::meta::AsArg;
+use crate::meta::ToGodot;
 use crate::{impl_shared_string_api, meta};
 
 /// Godot's reference counted string type.
@@ -314,6 +317,33 @@ impl fmt::Debug for GString {
     }
 }
 
+// ----------------------------------------------------------------------------------------------------------------------------------------------
+// Concatentation
+impl<'a, 'b> Add<&'b GString> for &'a GString {
+    type Output = GString;
+
+    fn add(self, other: &'b GString) -> GString {
+        str(&[self.to_variant(), other.to_variant()])
+    }
+}
+
+impl<'a> Add<GString> for &'a GString {
+    type Output = GString;
+
+    fn add(self, other: GString) -> GString {
+        str(&[self.to_variant(), other.to_variant()])
+    }
+}
+
+impl<'b> Add<&'b GString> for GString {
+    type Output = GString;
+
+    fn add(self, other: &'b GString) -> GString {
+        str(&[self.to_variant(), other.to_variant()])
+    }
+}
+
+
 // ----------------------------------------------------------------------------------------------------------------------------------------------
 // Conversion from/into Rust string-types
 

itest/rust/src/engine_tests/utilities_test.rs

@@ -44,6 +44,7 @@ fn utilities_str() {
 
     // TODO: implement GString==&str operator. Then look for "...".into() patterns and replace them.
     assert_eq!(concat, "12 is a true number".into());
+    assert_eq!(concat, &GString::from("12") + &GString::from(" is a ") + &GString::from("true") + &GString::from(" number"));
     assert_eq!(empty, GString::new());
 }