# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1548353549 -3600
# Node ID d2c64260113c9c96ab3e2ab1e5243a51f02cc83a
# Parent  d3a602461439eab5d14d27485bc1df18a92b1815
Fixed loop termination by using a dedicated exception instead of StopIteration.

diff -r d3a602461439 -r d2c64260113c common.py
--- a/common.py	Thu Jan 24 18:28:15 2019 +0100
+++ b/common.py	Thu Jan 24 19:12:29 2019 +0100
@@ -579,10 +579,14 @@
             # <t2> = <t1>.next
             # try:
             #     while True:
-            #         <var>... = <t2>()
-            #         ...
-            # except StopIteration:
+            #         try:
+            #             <var>... = <t2>()
+            #         except StopIteration:
+            #             raise LoopExit
+            #         {n.body}
+            # except LoopExit:
             #     {n.else_}
+            #     pass
 
             compiler.ast.Assign(
                 [compiler.ast.AssName(t2, "OP_ASSIGN")],
@@ -592,15 +596,18 @@
                 compiler.ast.While(
                     compiler.ast.Name("True"),
                     compiler.ast.Stmt([
-                        compiler.ast.Assign(
-                            [n.assign],
-                            compiler.ast.CallFunc(
-                                compiler.ast.Name(t2),
-                                []
-                                )),
+                        compiler.ast.TryExcept(
+                            compiler.ast.Assign(
+                                [n.assign],
+                                compiler.ast.CallFunc(
+                                    compiler.ast.Name(t2),
+                                    [])),
+                            [(compiler.ast.Name("StopIteration"), None,
+                              compiler.ast.Raise(compiler.ast.Name("LoopExit")))],
+                            None),
                         n.body]),
                     None),
-                [(compiler.ast.Name("StopIteration"), None, n.else_ or compiler.ast.Pass())],
+                [(compiler.ast.Name("LoopExit"), None, n.else_ or compiler.ast.Pass())],
                 None)
             ])
 
diff -r d3a602461439 -r d2c64260113c lib/__builtins__/__init__.py
--- a/lib/__builtins__/__init__.py	Thu Jan 24 18:28:15 2019 +0100
+++ b/lib/__builtins__/__init__.py	Thu Jan 24 19:12:29 2019 +0100
@@ -3,7 +3,7 @@
 """
 Simple built-in classes and functions.
 
-Copyright (C) 2015, 2016, 2017 Paul Boddie <paul@boddie.org.uk>
+Copyright (C) 2015, 2016, 2017, 2019 Paul Boddie <paul@boddie.org.uk>
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -35,6 +35,7 @@
     IndentationError,
     IndexError,
     IOError,
+    LoopExit,
     KeyError,
     KeyboardInterrupt,
     NotImplementedError,
diff -r d3a602461439 -r d2c64260113c lib/__builtins__/exception/__init__.py
--- a/lib/__builtins__/exception/__init__.py	Thu Jan 24 18:28:15 2019 +0100
+++ b/lib/__builtins__/exception/__init__.py	Thu Jan 24 19:12:29 2019 +0100
@@ -3,7 +3,7 @@
 """
 Exception objects.
 
-Copyright (C) 2015, 2016, 2017 Paul Boddie <paul@boddie.org.uk>
+Copyright (C) 2015, 2016, 2017, 2019 Paul Boddie <paul@boddie.org.uk>
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -25,6 +25,7 @@
 
 from __builtins__.exception.base import (
     IndexError,
+    LoopExit,
     KeyError,
     NotImplementedError,
     RuntimeError,
diff -r d3a602461439 -r d2c64260113c lib/__builtins__/exception/base.py
--- a/lib/__builtins__/exception/base.py	Thu Jan 24 18:28:15 2019 +0100
+++ b/lib/__builtins__/exception/base.py	Thu Jan 24 19:12:29 2019 +0100
@@ -3,7 +3,7 @@
 """
 Base exception objects. See __builtins__.core for the core exceptions.
 
-Copyright (C) 2015, 2016, 2018 Paul Boddie <paul@boddie.org.uk>
+Copyright (C) 2015, 2016, 2018, 2019 Paul Boddie <paul@boddie.org.uk>
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -61,6 +61,12 @@
 
         pass
 
+class LoopExit(Exception):
+
+    "An exception signalling the end of iteration in a loop."
+
+    pass
+
 class StopIteration(Exception):
 
     "An exception signalling the end of iteration."
diff -r d3a602461439 -r d2c64260113c tests/for.py
--- a/tests/for.py	Thu Jan 24 18:28:15 2019 +0100
+++ b/tests/for.py	Thu Jan 24 19:12:29 2019 +0100
@@ -1,5 +1,7 @@
 l = [1, 2, 3]
 
+# Test else clause.
+
 for i in l:
     print i             # 1
                         # 2
@@ -7,6 +9,8 @@
 else:
     print 4             # 4
 
+# Test break versus else clause.
+
 for i in l:
     print i             # 1
                         # 2
@@ -14,3 +18,17 @@
         break
 else:
     print 3
+
+# Test StopIteration in loop.
+
+try:
+    for i in l:
+        print i         # 1
+                        # 2
+        if i == 2:
+            raise StopIteration
+    else:
+        print 3
+
+except StopIteration:
+    print "stopped"     # stopped