Optimize substring assignation

Author: boriel

api/check.py

@@ -411,6 +411,12 @@ def is_block_accessed(block):
     return False
 
 
+def is_temporary_value(node) -> bool:
+    """ Returns if the AST node value is a variable or a temporary copy in the heap.
+    """
+    return node.token not in ('STRING', 'VAR') and node.t[0] not in ('_', '#')
+
+
 def common_type(a, b):
     """ Returns a type which is common for both a and b types.
     Returns None if no common types allowed.

arch/zx48k/translator.py

@@ -314,8 +314,13 @@ def visit_LETARRAY(self, node):
 
     def visit_LETSUBSTR(self, node):
         yield node.children[3]
-        self.ic_param(TYPE.string, node.children[3].t)
-        self.ic_param(TYPE.ubyte, 1)
+
+        if check.is_temporary_value(node.children[3]):
+            self.ic_param(TYPE.string, node.children[3].t)
+            self.ic_param(TYPE.ubyte, 1)
+        else:
+            self.ic_param(gl.PTR_TYPE, node.children[3].t)
+            self.ic_param(TYPE.ubyte, 0)
 
         yield node.children[1]
         self.ic_param(gl.PTR_TYPE, node.children[1].t)
@@ -333,6 +338,7 @@ def visit_LETARRAYSUBSTR(self, node):
         yield expr
         self.ic_param(TYPE.string, expr.t)
 
+        # TODO: this produces a memory leak
         if expr.token != 'STRING' and (expr.token != 'VAR' or expr.mangled[0] != '_'):
             self.ic_param(TYPE.ubyte, 1)  # If the argument is not a variable, it must be freed
         else: