handle parenthesis after lexing instead

lips/Lexer.lua

@@ -318,18 +318,14 @@ function Lexer:lex(_yield)
             end
             self:nextc()
             yield('DEF', buff)
+        elseif self.chr == ']' then
+            self:error('unmatched closing bracket')
         elseif self.chr == '(' then
             self:nextc()
-            local buff = self:read_chars('[%w_]')
-            if self.chr ~= ')' then
-                self:error('invalid register name')
-            end
+            yield('OPEN', '(')
+        elseif self.chr == ')' then
             self:nextc()
-            local up = buff:upper()
-            if not data.all_registers[up] then
-                self:error('not a register')
-            end
-            yield('DEREF', up)
+            yield('CLOSE', ')')
         elseif self.chr == '.' then
             self:nextc()
             local buff = self:read_chars('[%w]')
@@ -373,10 +369,6 @@ function Lexer:lex(_yield)
                 end
                 yield('LABELSYM', buff)
             end
-        elseif self.chr == ']' then
-            self:error('unmatched closing bracket')
-        elseif self.chr == ')' then
-            self:error('unmatched closing parenthesis')
         elseif self.chr == '+' or self.chr == '-' then
             local sign_chr = self.chr
             local sign = sign_chr == '+' and 1 or -1

lips/Muncher.lua

@@ -68,11 +68,19 @@ function Muncher:register(t)
 end
 
 function Muncher:deref()
-    if self.tt ~= 'DEREF' then
+    if self.tt ~= 'OPEN' then
+        self:error('expected opening parenthesis for dereferencing')
+    end
+    self:advance()
+    if self.tt ~= 'REG' then
         self:error('expected register to dereference')
     end
     local reg = self.tok
     self:advance()
+    if self.tt ~= 'CLOSE' then
+        self:error('expected closing parenthesis for dereferencing')
+    end
+    self:advance()
     return reg
 end
 

lips/Parser.lua

@@ -182,7 +182,7 @@ function Parser:instruction()
         local args = {}
         args.rt = self:register()
         self:optional_comma()
-        if self.tt == 'DEREF' then
+        if self.tt == 'OPEN' then
             args.offset = {'NUM', 0}
             args.base = self:deref()
         else -- NUM or LABELSYM