[oil-language] Create a token to parse for @{.myproc arg1}

Related to #799.

[refactor] Planning out parsing of where (x > 10)

Barely starting #955.

Author: Andy Chu

frontend/id_kind_def.py

@@ -215,6 +215,7 @@ def AddKinds(spec):
   spec.AddKind('Lit', [
       'Chars', 'VarLike', 'ArrayLhsOpen', 'ArrayLhsClose',
       'Splice',  # @func(a, b)
+      'AtLBraceDot',  # @{.myproc arg1}
       'Other', 'EscapedChar', 'RegexMeta',
       'LBracket', 'RBracket',  # for assoc array literals, static globs
       'Star', 'QMark',

frontend/lexer_def.py

@@ -325,6 +325,7 @@ def R(pat, tok_type):
 
   # @array and @func(1, c)
   R('@' + VAR_NAME_RE, Id.Lit_Splice),  # for Oil splicing
+  C('@{.', Id.Lit_AtLBraceDot),         # for split builtin sub @{.myproc arg1}
 
   R(FD_NUM + r'<', Id.Redir_Less),
   R(FD_NUM + r'>', Id.Redir_Great),

osh/cmd_parse.py

@@ -1661,22 +1661,29 @@ def ParseFunctionDef(self):
     self.lexer.PushHint(Id.Op_RParen, Id.Right_ShFunction)
     self._Next()
 
-    self._Eat2(Id.Right_ShFunction, 'Expected ) in function definition')
+    self._Peek()
+    if self.c_id == Id.Right_ShFunction:
+      # 'f ()' implies a function definition, since invoking it with no args
+      # would just be 'f'
+      self._Next()
 
-    after_name_spid = word_.LeftMostSpanForWord(self.cur_word) + 1
+      after_name_spid = word_.LeftMostSpanForWord(self.cur_word) + 1
 
-    self._NewlineOk()
+      self._NewlineOk()
 
-    func = command.ShFunction()
-    func.name = name
-    with ctx_VarChecker(self.var_checker, blame_tok):
-      func.body = self.ParseCompoundCommand()
+      func = command.ShFunction()
+      func.name = name
+      with ctx_VarChecker(self.var_checker, blame_tok):
+        func.body = self.ParseCompoundCommand()
 
-    # matches ParseKshFunctionDef below
-    func.spids.append(left_spid)
-    func.spids.append(left_spid)  # name_spid is same as left_spid in this case
-    func.spids.append(after_name_spid)
-    return func
+      # matches ParseKshFunctionDef below
+      func.spids.append(left_spid)
+      func.spids.append(left_spid)  # name_spid is same as left_spid in this case
+      func.spids.append(after_name_spid)
+      return func
+    else:
+      p_die('Expected ) in function definition', word=self.cur_word)
+      return None
 
   def ParseKshFunctionDef(self):
     # type: () -> command__ShFunction

osh/word_parse.py

@@ -1421,6 +1421,10 @@ def _MaybeReadWholeWord(self, is_first, lex_mode, parts):
         p_die('Unexpected token after array splice', token=self.cur_token)
       done = True
 
+    elif (is_first and self.parse_opts.parse_at() and
+          self.token_type == Id.Lit_AtLBraceDot):
+      p_die('TODO: @{.myproc builtin sub}', token=self.cur_token)
+
     elif (is_first and self.parse_opts.parse_at_all() and
           self.token_type == Id.Lit_At):
       # Because $[x] ${x} and perhaps $/x/ are reserved, it makes sense for @