[patsub] Fix crash in ${x/^} and ${x/!}

In the glob to ERE converter, we weren't handling the ^ and ! char class
operators outside of char classes.

Addresses issue reported in oils-for-unix#653.

frontend/lexer_def.py

@@ -626,7 +626,7 @@ def IsKeyword(name):
   C('*', Id.Glob_Star),
   C('?', Id.Glob_QMark),
 
-  # For negation.
+  # For negation.  Treated as operators inside [], but literals outside.
   C('!', Id.Glob_Bang),
   C('^', Id.Glob_Caret),
 

osh/glob_.py

@@ -268,10 +268,12 @@ def _GenerateERE(parts):
           out.append('\\')
         out.append(c)
 
-      elif part.id == Id.Glob_CleanLiterals:
+      # ! is only for char class
+      elif part.id in (Id.Glob_CleanLiterals, Id.Glob_Bang):
         out.append(part.s)  # e.g. 'py' doesn't need to be escaped
 
-      elif part.id == Id.Glob_OtherLiteral:
+      # ^ is only for char class
+      elif part.id in( Id.Glob_OtherLiteral, Id.Glob_Caret):
         assert len(part.s) == 1, part.s
         c = part.s
         if c in _REGEX_CHARS_TO_ESCAPE:
@@ -288,6 +290,9 @@ def _GenerateERE(parts):
       elif part.id == Id.Glob_BadBackslash:
         out.append('\\\\')
 
+      elif part.id == Id.Glob_Caret:
+        out.append('^')
+
       else:
         raise AssertionError(part.id)
 

spec/dbracket.test.sh

@@ -350,3 +350,13 @@ cat $TMP/x.txt
 --
 STDERR
 ## END
+
+#### special chars
+[[ ^ == ^ ]]
+echo caret $?
+[[ '!' == ! ]]
+echo bang $?
+## STDOUT:
+caret 0
+bang 0
+## END

spec/var-op-patsub.test.sh

@@ -186,3 +186,31 @@ _μ_ and _μ_
 _μ_ and _μ_
 _μ_ and _μ_
 ## END
+
+#### ${x/^} regression
+x=abc
+echo ${x/^}
+echo ${x/!}
+
+y=^^^
+echo ${y/^}
+echo ${y/!}
+
+z=!!!
+echo ${z/^}
+echo ${z/!}
+
+s=a^b!c
+echo ${s/a^}
+echo ${s/b!}
+
+## STDOUT:
+abc
+abc
+^^
+^^^
+!!!
+!!
+b!c
+a^c
+## END