more pythonic

book.tex

@@ -15058,9 +15058,7 @@ class TypeCheckLlambda(TypeCheckLfun):
         e.has_type = ty
         match ty:
           case FunctionType(params_t, return_t):
-            new_env = {x:t for (x,t) in env.items()}
-            for (p,t) in zip(params, params_t):
-                new_env[p] = t
+            new_env = env.copy().update(zip(params, params_t))
             self.check_exp(body, return_t, new_env)
           case _:
             raise Exception('lambda does not have type ' + str(ty))
@@ -15092,9 +15090,7 @@ class TypeCheckLlambda(TypeCheckLfun):
       return
     match ss[0]:
       case FunctionDef(name, params, body, dl, returns, comment):
-        new_env = {x: t for (x,t) in env.items()}
-        for (x,t) in params:
-            new_env[x] = t
+        new_env = env.copy().update(params)
         rt = self.check_stmts(body, returns, new_env)
         self.check_stmts(ss[1:], return_ty, env)
       case Return(value):