Fix the obnoxious issue with globals propagation in full expressions.

Fixed by backtracking in the parser, and keeping a copy of the original expression if it's a simple_expr, which is used for output in place of the folded one.

There's still the potential issue that if a global is optimized away, then it will "come back" during output and cause an error because the definition is missing.

lslopt/lsloptimizer.py

@@ -46,6 +46,16 @@ class optimizer(object):
             return value
         return {'nt':'CAST', 't':newtype, 'ch':[value]}
 
+    def CopyNode(self, node):
+        # This is mainly for simple_expr so not a big deal.
+        ret = node.copy()
+        if 'ch' in ret:
+            new = []
+            for subnode in ret['ch']:
+                new.append(self.CopyNode(subnode))
+            ret['ch'] = new
+        return ret
+
     def FoldTree(self, parent, index):
         """Recursively traverse the tree to fold constants, changing it in
         place.
@@ -512,10 +522,14 @@ class optimizer(object):
 
         if nt == 'DECL':
             if child:
-                # TODO: Decide if child is a simple_expr.
-                # If it is, then we should keep the original
-                # attached to the folded node and use it in the output.
-                self.FoldTree(child, 0)
+                # Check if child is a simple_expr. If it is, then we keep the
+                # original attached to the folded node and use it in the output.
+                if child[0].pop('Simple', False):
+                    orig = self.CopyNode(child[0])
+                    self.FoldTree(child, 0)
+                    child[0]['orig'] = orig
+                else:
+                    self.FoldTree(child, 0)
                 # Remove assignment if integer zero.
                 if node['t'] == 'integer' and child[0]['nt'] == 'CONST' \
                    and not child[0]['value']:
@@ -569,7 +583,7 @@ class optimizer(object):
                 self.FoldTree(tree, idx)
                 self.globalmode = False
                 if not self.IsValidGlobalConstant(tree[idx]):
-                    warning('WARNING: Expression does not collapse to a single constant.')
+                    warning('WARNING: Expression does not resolve to a single constant.')
             else:
                 self.FoldTree(tree, idx)
 

lslopt/lsloutput.py

@@ -265,7 +265,10 @@ class outscript(object):
         if nt == 'DECL':
             ret = self.dent() + node['t'] + ' ' + node['name']
             if child:
-                ret += ' = ' + self.OutExpr(child[0])
+                if 'orig' in child[0]:
+                    ret += ' = ' + self.OutExpr(child[0]['orig'])
+                else:
+                    ret += ' = ' + self.OutExpr(child[0])
             return ret + ';\n'
         if nt == ';':
             return self.dent() + ';\n'

lslopt/lslparse.py

@@ -1465,7 +1465,7 @@ class parser(object):
                 raise EParseAlreadyDefined(self)
             self.NextToken()
 
-            if self.tok[0] == '=' or self.tok[0] == ';':
+            if self.tok[0] in ('=', ';'):
                 # This is a variable definition
                 if typ is None: # Typeless variables are not allowed
                     raise EParseSyntax(self)
@@ -1474,11 +1474,27 @@ class parser(object):
                     self.NextToken()
                     if self.extendedglobalexpr:
                         self.globalmode = True # Disallow forward globals.
-                        value = self.Parse_expression() # Use advanced expression evaluation.
+                        # Mark backtracking position
+                        pos = self.pos
+                        errorpos = self.errorpos
+                        tok = self.tok
+                        try:
+                            value = self.Parse_simple_expr()
+                            self.expect(';')
+                            value['Simple'] = True # Success - mark it as simple
+                        except EParse:
+                            # Backtrack
+                            self.pos = pos
+                            self.errorpos = errorpos
+                            self.tok = tok
+                            # Use advanced expression evaluation.
+                            value = self.Parse_expression()
+                            self.expect(';')
                         self.globalmode = False # Allow forward globals again.
                     else:
-                        value = self.Parse_simple_expr() # Use LSL's dull global expression.
-                    self.expect(';')
+                        # Use LSL's dull global expression.
+                        value = self.Parse_simple_expr()
+                        self.expect(';')
                     self.NextToken()
                 else: # must be semicolon
                     self.NextToken()