From dfb4499a70ef3c84ebde7d1eda10a8173f1e8a9f Mon Sep 17 00:00:00 2001
From: glx <glx@openttd.org>
Date: Sat, 21 Dec 2019 18:46:05 +0100
Subject: [PATCH] Add: is_read_only()

---
 nml/expression/array.py           | 3 +++
 nml/expression/base_expression.py | 8 ++++++++
 nml/expression/bin_not.py         | 6 ++++++
 nml/expression/binop.py           | 3 +++
 nml/expression/bitmask.py         | 3 +++
 nml/expression/boolean.py         | 3 +++
 nml/expression/storage_op.py      | 4 ++++
 nml/expression/ternaryop.py       | 3 +++
 8 files changed, 33 insertions(+)

diff --git a/nml/expression/array.py b/nml/expression/array.py
index 5b88bb12..f74ede13 100644
--- a/nml/expression/array.py
+++ b/nml/expression/array.py
@@ -35,3 +35,6 @@ def reduce(self, id_dicts = [], unknown_id_fatal = True):
     def collect_references(self):
         from itertools import chain
         return list(chain.from_iterable(v.collect_references() for v in self.values))
+
+    def is_read_only(self):
+        return all(v.is_read_only() for v in self.values)
diff --git a/nml/expression/base_expression.py b/nml/expression/base_expression.py
index a03b9103..366271c5 100644
--- a/nml/expression/base_expression.py
+++ b/nml/expression/base_expression.py
@@ -110,6 +110,14 @@ def collect_references(self):
         """
         return []
 
+    def is_read_only(self):
+        """
+        Check if this expression store values.
+
+        @return: True if the expression doesn't store values.
+        """
+        return True
+
     def is_boolean(self):
         """
         Check if this expression is limited to 0 or 1 as value.
diff --git a/nml/expression/bin_not.py b/nml/expression/bin_not.py
index 7a5d111b..43650895 100644
--- a/nml/expression/bin_not.py
+++ b/nml/expression/bin_not.py
@@ -44,6 +44,9 @@ def supported_by_actionD(self, raise_error):
     def collect_references(self):
         return self.expr.collect_references()
 
+    def is_read_only(self):
+        return self.expr.is_read_only()
+
     def __str__(self):
         return "~" + str(self.expr)
 
@@ -82,6 +85,9 @@ def supported_by_actionD(self, raise_error):
     def collect_references(self):
         return self.expr.collect_references()
 
+    def is_read_only(self):
+        return self.expr.is_read_only()
+
     def is_boolean(self):
         return True
 
diff --git a/nml/expression/binop.py b/nml/expression/binop.py
index e7e8eeb6..b7e16e34 100644
--- a/nml/expression/binop.py
+++ b/nml/expression/binop.py
@@ -184,6 +184,9 @@ def supported_by_actionD(self, raise_error):
     def collect_references(self):
         return self.expr1.collect_references() + self.expr2.collect_references()
 
+    def is_read_only(self):
+        return self.expr1.is_read_only() and self.expr2.is_read_only()
+
     def is_boolean(self):
         if self.op in (nmlop.AND, nmlop.OR, nmlop.XOR):
             return self.expr1.is_boolean() and self.expr2.is_boolean()
diff --git a/nml/expression/bitmask.py b/nml/expression/bitmask.py
index 8df4afa0..a9cd5ba7 100644
--- a/nml/expression/bitmask.py
+++ b/nml/expression/bitmask.py
@@ -43,5 +43,8 @@ def collect_references(self):
         from itertools import chain
         return list(chain.from_iterable(v.collect_references() for v in self.values))
 
+    def is_read_only(self):
+        return all(v.is_read_only() for v in self.values)
+
     def __str__(self):
         return "bitmask(" + ", ".join(str(e) for e in self.values) + ")"
diff --git a/nml/expression/boolean.py b/nml/expression/boolean.py
index 1fc1c532..859b6674 100644
--- a/nml/expression/boolean.py
+++ b/nml/expression/boolean.py
@@ -47,6 +47,9 @@ def supported_by_actionD(self, raise_error):
     def collect_references(self):
         return self.expr.collect_references()
 
+    def is_read_only(self):
+        return self.expr.is_read_only()
+
     def is_boolean(self):
         return True
 
diff --git a/nml/expression/storage_op.py b/nml/expression/storage_op.py
index afa0fd54..ba5d2598 100644
--- a/nml/expression/storage_op.py
+++ b/nml/expression/storage_op.py
@@ -124,3 +124,7 @@ def supported_by_actionD(self, raise_error):
 
     def collect_references(self):
         return self.register.collect_references() + (self.value.collect_references() if self.value is not None else [])
+
+    def is_read_only(self):
+        assert(self.info['store'] == (self.value is not None))
+        return (not self.info['store']) and self.register.is_read_only()
diff --git a/nml/expression/ternaryop.py b/nml/expression/ternaryop.py
index a0c6e57f..fc270408 100644
--- a/nml/expression/ternaryop.py
+++ b/nml/expression/ternaryop.py
@@ -54,6 +54,9 @@ def supported_by_actionD(self, raise_error):
     def collect_references(self):
         return self.guard.collect_references() + self.expr1.collect_references() + self.expr2.collect_references()
 
+    def is_read_only(self):
+        return self.expr1.is_read_only() and self.expr2.is_read_only()
+
     def is_boolean(self):
         return self.expr1.is_boolean() and self.expr2.is_boolean()