Extract goto to a separate compat feature

lib/1.2/dml-builtins.dml

@@ -212,6 +212,7 @@ template device {
     parameter _compat_io_memory auto;
     parameter _compat_dml12_inline auto;
     parameter _compat_dml12_not auto;
+    parameter _compat_dml12_goto auto;
     parameter _compat_dml12_misc auto;
     parameter _compat_dml12_int auto;
 

lib/1.4/dml-builtins.dml

@@ -546,6 +546,7 @@ template device {
     param _compat_io_memory auto;
     param _compat_dml12_inline auto;
     param _compat_dml12_not auto;
+    param _compat_dml12_goto auto;
     param _compat_dml12_misc auto;
     param _compat_dml12_int auto;
 

py/dml/codegen.py

@@ -2545,7 +2545,7 @@ def stmt_assert(stmt, location, scope):
 @statement_dispatcher
 def stmt_goto(stmt, location, scope):
     [label] = stmt.args
-    if compat.dml12_misc not in dml.globals.enabled_compat:
+    if compat.dml12_goto not in dml.globals.enabled_compat:
         report(ESYNTAX(stmt.site, 'goto', 'goto statement not allowed'))
     return [mkGoto(stmt.site, label)]
 

py/dml/compat.py

@@ -137,8 +137,6 @@ class dml12_misc(CompatFeature):
 
     * the `typeof` operator on an expression that isn't an lvalue
 
-    * the `goto` statement
-
     * `select` statements over `vect` types
 
     * Passing a string literal in a (non-`const`) `char *` method argument
@@ -169,6 +167,18 @@ class dml12_misc(CompatFeature):
     last_api_version = api_6
 
 
+@feature
+class dml12_goto(CompatFeature):
+    '''The `goto` statement is deprecated; this compatibility feature
+    preserves it. Most `goto` based control structures can be reworked by
+    changing the `goto` into a `throw`, and its label into a `catch`
+    block; since this is sometimes nontrivial, it can be useful to disable
+    the `goto` statement separately.
+    '''
+    short = "Disable the goto statement in DML 1.2"
+    last_api_version = api_6
+
+
 @feature
 class dml12_int(CompatFeature):
     '''This compatibility feature affects many semantic details of

py/dml/dmlc.py

@@ -410,7 +410,7 @@ def main(argv):
 
     parser.add_argument('--strict-dml12', action='store_true',
                         help='Alias for --no-compat=dml12_inline'
-                        ',dml12_not,dml12_misc,dml12_int')
+                        ',dml12_not,dml12_goto,dml12_misc,dml12_int')
     parser.add_argument('--strict-int', action='store_true',
                         help='Alias for --no-compat=dml12_int')
 
@@ -608,7 +608,8 @@ def main(argv):
 
     if options.strict_dml12:
         for feature in [compat.dml12_inline, compat.dml12_not,
-                        compat.dml12_misc, compat.dml12_int]:
+                        compat.dml12_goto, compat.dml12_misc,
+                        compat.dml12_int]:
             tag = feature.tag()
             if tag in features:
                 del features[tag]