From 697e80cb16ef40698fbccb876e73a8fe57dabf0a Mon Sep 17 00:00:00 2001
From: Sei Lisa <sei-lisa@email.fake>
Date: Sat, 7 May 2016 02:38:54 +0200
Subject: [PATCH] Rather than reproduce the broken behaviour, throw an error on
 missing default.

Changed my mind. This looks saner. Now, if the 'default:' label is missing, an error will be thrown by default. It has to be explicitly disabled if normal C-like behaviour is desired (namely to jump to the 'break' label if no condition is met).
---
 lslopt/lslparse.py | 26 ++++++++++++++++----------
 main.py            |  9 +++------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/lslopt/lslparse.py b/lslopt/lslparse.py
index f4acebf..7d7edcf 100644
--- a/lslopt/lslparse.py
+++ b/lslopt/lslparse.py
@@ -148,6 +148,12 @@ class EParseManyDefaults(EParse):
         super(EParseManyDefaults, self).__init__(parser,
             u"multiple 'default' labels inside 'switch' statement")
 
+class EParseMissingDefault(EParse):
+    def __init__(self, parser):
+        super(EParseMissingDefault, self).__init__(parser,
+            u"Missing 'default:' label inside 'switch' statement; disable"
+            u" option 'errmissingdefault' to disable this error.")
+
 class EParseInvalidBreak(EParse):
     def __init__(self, parser):
         super(EParseInvalidBreak, self).__init__(parser,
@@ -1674,15 +1680,15 @@ list lazy_list_set(list L, integer i, list v)
                     ]})
 
             if switchcasedefault is None:
-                warning("No 'default:' label in switch statement")
-                if self.brokennodefault:
-                    warning("Broken behaviour active - falling through")
-                if not self.brokennodefault:
-                    switchcasedefault = brk
-                    self.breakstack[-1][2] = True
-            if switchcasedefault is not None:
-                prelude.append({'nt':'JUMP', 't':None, 'name':switchcasedefault,
-                    'scope':blkscope})
+                if self.errmissingdefault:
+                    raise EParseMissingDefault(self)
+                switchcasedefault = brk
+                self.breakstack[-1][2] = True
+            # TODO: Check if this JUMP is necessary
+            # (it won't be if the default label is the next instruction)
+            # This is arguably better done after DCR.
+            prelude.append({'nt':'JUMP', 't':None, 'name':switchcasedefault,
+                'scope':blkscope})
             last = self.breakstack.pop()
             if last[2]:
                 blk.append({'nt':'@', 'name':brk, 'scope':blkscope})
@@ -2317,7 +2323,7 @@ list lazy_list_set(list L, integer i, list v)
             self.keywords |= frozenset(('switch', 'case', 'break'))
 
         # Broken behaviour in the absence of a default: label in a switch stmt.
-        self.brokennodefault = 'brokennodefault' in options
+        self.errmissingdefault = 'errmissingdefault' in options
 
         # Allow brackets for assignment of list elements e.g. mylist[5]=4
         self.lazylists = 'lazylists' in options
diff --git a/main.py b/main.py
index 88deec2..86ee201 100755
--- a/main.py
+++ b/main.py
@@ -228,11 +228,6 @@ Optimizer options (+ means active by default, - means inactive by default):
                        will go to the last label with that name). This flag
                        works around that limitation by replacing the names of
                        the labels in the output with unique ones.
-  brokennodefault    + Mimic Firestorm's legacy broken behaviour when the
-                       'default' label in a switch statement is absent. Rather
-                       than jumping to the end of the switch in that case
-                       (which is how it behaves when this option is not set),
-                       it falls through and executes the first 'case' label.
 
   Deprecated / compatibility syntax extensions options:
 
@@ -247,6 +242,8 @@ Optimizer options (+ means active by default, - means inactive by default):
                        Like lazylists, it's implemented for compatibility with
                        Firestorm, but not recommended. Note that the operand to
                        switch() may be evaluated more than once.
+  errmissingdefault  + Throw an error in case the 'default:' label of a switch
+                       statement is missing.
   funcoverride       - Allow duplicate function definitions to override the
                        previous definition. For compatibility with Firestorm's
                        optimizer.
@@ -305,7 +302,7 @@ def main():
     # Default options
     options = set(('extendedglobalexpr','extendedtypecast','extendedassignment',
         'allowkeyconcat','allowmultistrings','skippreproc','optimize',
-        'optsigns','optfloats','constfold','dcr', 'brokennodefault',
+        'optsigns','optfloats','constfold','dcr','errmissingdefault',
         ))
 
     try: