Drop the bare names that were sprinkled everywhere in the generated AST.

This closes #162

We make sure not to drop *explicitly written* bare names.

hy/compiler.py

@@ -193,9 +193,13 @@ class Result(object):
         This is useful when we want to use the stored expression in a
         statement context (for instance in a code branch).
 
+        We drop ast.Names if they are appended to statements, as they
+        can't have any side effect. "Bare" names still get converted to
+        statements.
+
         If there is no expression context, return an empty result.
         """
-        if self.expr:
+        if self.expr and not (isinstance(self.expr, ast.Name) and self.stmts):
             return Result() + ast.Expr(lineno=self.expr.lineno,
                                        col_offset=self.expr.col_offset,
                                        value=self.expr)

tests/compilers/test_compiler.py

@@ -1,4 +1,5 @@
 # Copyright (c) 2013 Julien Danjou <julien@danjou.info>
+# Copyright (c) 2013 Nicolas Dandrimont <nicolas.dandrimont@crans.org>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a
 # copy of this software and associated documentation files (the "Software"),
@@ -29,6 +30,7 @@ else:
 
 from hy.models.expression import HyExpression
 from hy.models.list import HyList
+from hy.models.symbol import HySymbol
 from hy.compiler import HyASTCompiler
 
 
@@ -63,3 +65,24 @@ class HyASTCompilerTest(unittest.TestCase):
         self.assertIsInstance(stmt.body[0], ast.Pass)
 
         self.assertIsInstance(ret.expr, ast.Name)
+
+    def test_compiler_bare_names(self):
+        """Check that the compiler doesn't drop bare names from code branches"""
+        ret = self.c.compile(self._make_expression(HySymbol("do"),
+                                                   HySymbol("a"),
+                                                   HySymbol("b"),
+                                                   HySymbol("c")))
+
+        # We expect two statements and a final expr.
+        self.assertEqual(len(ret.stmts), 2)
+        stmt = ret.stmts[0]
+        self.assertIsInstance(stmt, ast.Expr)
+        self.assertIsInstance(stmt.value, ast.Name)
+        self.assertEqual(stmt.value.id, "a")
+        stmt = ret.stmts[1]
+        self.assertIsInstance(stmt, ast.Expr)
+        self.assertIsInstance(stmt.value, ast.Name)
+        self.assertEqual(stmt.value.id, "b")
+        expr = ret.expr
+        self.assertIsInstance(expr, ast.Name)
+        self.assertEqual(expr.id, "c")