Add GString == &str equality operator

Easier than converting to String/GString, and requires no allocation.

Author: Bromeon

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

@@ -323,6 +323,21 @@ impl fmt::Debug for GString {
     }
 }
 
+// ----------------------------------------------------------------------------------------------------------------------------------------------
+// Comparison with Rust strings
+
+// API design:
+// * StringName and NodePath don't implement PartialEq<&str> yet, because they require allocation (convert to GString).
+//   == should ideally not allocate.
+// * Reverse `impl PartialEq<GString> for &str` is not implemented now. Comparisons usually take the form of variable == "literal".
+//   Can be added later if there are good use-cases.
+
+impl PartialEq<&str> for GString {
+    fn eq(&self, other: &&str) -> bool {
+        self.chars().iter().copied().eq(other.chars())
+    }
+}
+
 // ----------------------------------------------------------------------------------------------------------------------------------------------
 // Conversion from/into Rust string-types
 

itest/rust/src/builtin_tests/string/gstring_test.rs

@@ -40,6 +40,13 @@ fn string_equality() {
     assert_ne!(string, different);
 }
 
+#[itest]
+fn string_eq_str() {
+    let gstring = GString::from("hello");
+    assert_eq!(gstring, "hello");
+    assert_ne!(gstring, "hallo");
+}
+
 #[itest]
 fn string_ordering() {
     let low = GString::from("Alpha");