From da4b398bf0bc15b5f39a9dca798812cd6e4ee618 Mon Sep 17 00:00:00 2001
From: Gleb Koval <gleb@koval.net>
Date: Sun, 2 Feb 2025 13:30:33 +0000
Subject: [PATCH] fix: do not allow negation of a positive int literal

---
 src/main/wacc/lexer.scala  | 2 ++
 src/main/wacc/parser.scala | 6 +++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/main/wacc/lexer.scala b/src/main/wacc/lexer.scala
index 4351294..094ac12 100644
--- a/src/main/wacc/lexer.scala
+++ b/src/main/wacc/lexer.scala
@@ -1,6 +1,7 @@
 package wacc
 
 import parsley.Parsley
+import parsley.character
 import parsley.token.{Basic, Lexer}
 import parsley.token.descriptions.*
 
@@ -45,6 +46,7 @@ object lexer {
   private val lexer = Lexer(desc)
   val ident = lexer.lexeme.names.identifier
   val integer = lexer.lexeme.integer.decimal32[Int]
+  val negateCheck = lexer.nonlexeme.symbol("-") ~> character.digit
   val charLit = lexer.lexeme.character.ascii
   val stringLit = lexer.lexeme.string.ascii
   val implicits = lexer.lexeme.symbol.implicits
diff --git a/src/main/wacc/parser.scala b/src/main/wacc/parser.scala
index 98e9484..84ee093 100644
--- a/src/main/wacc/parser.scala
+++ b/src/main/wacc/parser.scala
@@ -2,7 +2,7 @@ package wacc
 
 import parsley.Result
 import parsley.Parsley
-import parsley.Parsley.{atomic, many, pure}
+import parsley.Parsley.{atomic, many, notFollowedBy, pure}
 import parsley.combinator.{countSome, sepBy}
 import parsley.expr.{precedence, SOps, InfixL, InfixN, InfixR, Prefix, Atoms}
 import parsley.errors.combinator._
@@ -11,7 +11,7 @@ import cats.data.NonEmptyList
 
 object parser {
   import lexer.implicits.implicitSymbol
-  import lexer.{ident, integer, charLit, stringLit}
+  import lexer.{ident, integer, charLit, stringLit, negateCheck}
   import ast._
 
   def parse(input: String): Result[String, Program] = parser.parse(input)
@@ -32,7 +32,7 @@ object parser {
       SOps(InfixL)(Mul from "*", Div from "/", Mod from "%") +:
       SOps(Prefix)(
         Not from "!",
-        Negate from "-",
+        Negate from (notFollowedBy(negateCheck) ~> "-"),
         Len from "len",
         Ord from "ord",
         Chr from "chr"