Merge pull request #1886 from Kodiologist/empty-expr

Fixes for empty expressions

NEWS.rst

@@ -13,6 +13,8 @@ Bug Fixes
 * Improved support for nesting anaphoric macros by only applying
   symbol replacement where absolutely necessary.
 * Quoted f-strings are no longer evaluated prematurely.
+* Fixed a regression in the production of error messages for empty
+  expressions.
 
 0.18.0
 ==============================

hy/macros.py

@@ -308,10 +308,7 @@ def macroexpand(tree, module, compiler=None, once=False):
 
     assert not compiler or compiler.module == module
 
-    while True:
-
-        if not isinstance(tree, HyExpression) or tree == []:
-            break
+    while isinstance(tree, HyExpression) and tree:
 
         fn = tree[0]
         if fn in ("quote", "quasiquote") or not isinstance(fn, HySymbol):

tests/compilers/test_ast.py

@@ -7,7 +7,7 @@ from __future__ import unicode_literals
 
 from hy import HyString
 from hy.compiler import hy_compile, hy_eval
-from hy.errors import HyCompileError, HyLanguageError, HyError
+from hy.errors import HyLanguageError, HyError
 from hy.lex import hy_parse
 from hy.lex.exceptions import LexException, PrematureEndOfInput
 from hy._compat import PY36
@@ -36,14 +36,11 @@ def can_eval(expr):
 def cant_compile(expr):
     with pytest.raises(HyError) as excinfo:
         hy_compile(hy_parse(expr), __name__)
-
-    if issubclass(excinfo.type, HyLanguageError):
-        assert excinfo.value.msg
-        return excinfo.value
-    elif issubclass(excinfo.type, HyCompileError):
-        # Anything that can't be compiled should raise a user friendly
-        # error, otherwise it's a compiler bug.
-        return excinfo.value
+    # Anything that can't be compiled should raise a user friendly
+    # error, otherwise it's a compiler bug.
+    assert issubclass(excinfo.type, HyLanguageError)
+    assert excinfo.value.msg
+    return excinfo.value
 
 
 def s(x):