Add __add__ to String which joins and fix bug allowing preserved binary methods

Author: saulshanabrook

python/egglog/builtins.py

@@ -103,6 +103,10 @@ def value(self) -> str:
     @method(egg_fn="replace")
     def replace(self, old: StringLike, new: StringLike) -> String: ...
 
+    @method(preserve=True)
+    def __add__(self, other: StringLike) -> String:
+        return join(self, other)
+
 
 StringLike: TypeAlias = String | str
 

python/egglog/runtime.py

@@ -635,14 +635,22 @@ def _defined_method(self: RuntimeExpr, *args, __name: str = name, **kwargs):
 
 
 for name, r_method in itertools.product(NUMERIC_BINARY_METHODS, (False, True)):
+    method_name = f"__r{name[2:]}" if r_method else name
 
-    def _numeric_binary_method(self: object, other: object, name: str = name, r_method: bool = r_method) -> object:
+    def _numeric_binary_method(
+        self: object, other: object, name: str = name, r_method: bool = r_method, method_name: str = method_name
+    ) -> object:
         """
         Implements numeric binary operations.
 
         Tries to find the minimum cost conversion of either the LHS or the RHS, by finding all methods with either
         the LHS or the RHS as exactly the right type and then upcasting the other to that type.
         """
+        # First check if we have a preserved method for this:
+        if isinstance(self, RuntimeExpr) and (
+            (preserved_method := self.__egg_class_decl__.preserved_methods.get(method_name)) is not None
+        ):
+            return preserved_method.__get__(self)(other)
         # 1. switch if reversed method
         if r_method:
             self, other = other, self
@@ -668,7 +676,6 @@ def _numeric_binary_method(self: object, other: object, name: str = name, r_meth
         fn = RuntimeFunction(Thunk.value(self.__egg_decls__), Thunk.value(method_ref), self)
         return fn(other)
 
-    method_name = f"__r{name[2:]}" if r_method else name
     setattr(RuntimeExpr, method_name, _numeric_binary_method)