Merge pull request #1586 from Kodiologist/multi-expr-try

Fix a bug that caused `try` to drop expressions

NEWS.rst

@@ -50,6 +50,7 @@ Bug Fixes
 * Fixed bugs that caused `defclass` to drop statements or crash
 * Fixed a REPL crash caused by illegle unicode escape string inputs
 * `NaN` can no longer create an infinite loop during macro-expansion
+* Fixed a bug that caused `try` to drop expressions
 
 Misc. Improvements
 ----------------------------

hy/compiler.py

@@ -790,13 +790,14 @@ class HyASTCompiler(object):
         expr.pop(0)  # try
 
         # (try something somethingelse…)
-        body = Result()
+        body = []
         # Check against HyExpression and HySymbol to avoid incorrectly
         # matching [except ...] or ("except" ...)
         while expr and not (isinstance(expr[0], HyExpression)
                             and isinstance(expr[0][0], HySymbol)
                             and expr[0][0] in ("except", "else", "finally")):
-            body += self.compile(expr.pop(0))
+            body.append(expr.pop(0))
+        body = self._compile_branch(body)
 
         var = self.get_anon_var()
         name = asty.Name(expr, id=ast_str(var), ctx=ast.Store())
@@ -805,8 +806,6 @@ class HyASTCompiler(object):
         returnable = Result(expr=expr_name, temp_variables=[expr_name, name],
                             contains_yield=body.contains_yield)
 
-        if not all(expr):
-            raise HyTypeError(expr, "Empty list not allowed in `try'")
         handler_results = Result()
         handlers = []
         while expr and expr[0][0] == HySymbol("except"):
@@ -846,7 +845,6 @@ class HyASTCompiler(object):
 
         body += body.expr_as_stmt() if orelse else asty.Assign(
             expr, targets=[name], value=body.force_expr)
-
         body = body.stmts or [asty.Pass(expr)]
 
         if PY3:

tests/native_tests/language.hy

@@ -584,18 +584,27 @@
   (do))
 
 
-(defn test-exceptions []
-  "NATIVE: test Exceptions"
+(defn test-try []
 
   (try (do) (except []))
 
   (try (do) (except [IOError]) (except []))
 
-  ; test that multiple expressions in a try get evaluated
+  ; test that multiple statements in a try get evaluated
   (setv value 0)
   (try (+= value 1) (+= value 2)  (except [IOError]) (except []))
   (assert (= value 3))
 
+  ; test that multiple expressions in a try get evaluated
+  ; https://github.com/hylang/hy/issues/1584
+  (setv l [])
+  (defn f [] (.append l 1))
+  (try (f) (f) (f) (except [IOError]))
+  (assert (= l [1 1 1]))
+  (setv l [])
+  (try (f) (f) (f) (except [IOError]) (else (f)))
+  (assert (= l [1 1 1 1]))
+
   ;; Test correct (raise)
   (setv passed False)
   (try