try: allow empty body

Signed-off-by: Julien Danjou <julien@danjou.info>

hy/compiler.py

@@ -176,7 +176,6 @@ class HyASTCompiler(object):
             tback=None)
 
     @builds("try")
-    @checkargs(min=1)
     def compile_try_expression(self, expr):
         expr.pop(0)  # try
 
@@ -186,10 +185,16 @@ class HyASTCompiler(object):
         else:
             Try = ast.TryExcept
 
+        if len(expr) == 0:
+            body = [ast.Pass(lineno=expr.start_line,
+                             col_offset=expr.start_column)]
+        else:
+            body = self._code_branch(self.compile(expr.pop(0)))
+
         return Try(
             lineno=expr.start_line,
             col_offset=expr.start_column,
-            body=self._code_branch(self.compile(expr.pop(0))),
+            body=body,
             handlers=[self.compile(s) for s in expr],
             finalbody=[],
             orelse=[])

tests/compilers/test_ast.py

@@ -116,14 +116,10 @@ def test_ast_bad_raise():
 
 def test_ast_good_try():
     "Make sure AST can compile valid try"
+    hy_compile(tokenize("(try)"))
     hy_compile(tokenize("(try 1)"))
 
 
-def test_ast_bad_try():
-    "Make sure AST can't compile invalid try"
-    cant_compile("(try)")
-
-
 def test_ast_good_catch():
     "Make sure AST can compile valid catch"
     hy_compile(tokenize("(catch)"))

tests/native_tests/language.hy

@@ -162,6 +162,9 @@
 
 (defn test-exceptions []
   "NATIVE: test Exceptions"
+
+  (try)
+
   (try
     (raise (KeyError))
     (catch [[IOError]] (assert false))