From 60ad7b994c2126346c19769a1a5f5c8f679a05ee Mon Sep 17 00:00:00 2001
From: Tolmachev Igor <me@igorek.dev>
Date: Sat, 9 May 2026 15:25:49 +0300
Subject: Fix lexer processing [+-].\d as symbol instead of number

Extended lookahead in the number branch to 3 chars.

Added tests for "-.5", "+.5", "-.0" in test_numbers and for
"-.", "+.", ".", "+.a", "-.a" in test_ambiguous.
---
 compiler/src/lexer/mod.rs   |  8 ++++++--
 compiler/src/lexer/tests.rs | 10 +++++++++-
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/compiler/src/lexer/mod.rs b/compiler/src/lexer/mod.rs
index 464d88e..f3c8b76 100644
--- a/compiler/src/lexer/mod.rs
+++ b/compiler/src/lexer/mod.rs
@@ -146,8 +146,12 @@ impl<'a> Iterator for Lexer<'a> {
 
             // Number
             ch if ch.is_ascii_digit()
-                || matches!(ch, '+' | '-' | '.')
-                    && self.peek_nth(1).is_some_and(|ch| ch.is_ascii_digit()) =>
+                || ch == '.' && self.peek_nth(1).is_some_and(|ch| ch.is_ascii_digit())
+                || matches!(ch, '+' | '-')
+                    && self.peek_nth(1).is_some_and(|ch| ch.is_ascii_digit())
+                || matches!(ch, '+' | '-')
+                    && self.peek_nth(1).is_some_and(|ch| ch == '.')
+                    && self.peek_nth(2).is_some_and(|ch| ch.is_ascii_digit()) =>
             {
                 Token::Number(self.next_atom())
             }
diff --git a/compiler/src/lexer/tests.rs b/compiler/src/lexer/tests.rs
index 89575c7..6f96c65 100644
--- a/compiler/src/lexer/tests.rs
+++ b/compiler/src/lexer/tests.rs
@@ -1,7 +1,7 @@
 use crate::span::Pos;
 
 use super::Token::*;
-use super::*;
+use super::{Lexer, Token};
 
 fn tokenize<'a>(input: &'a str) -> Vec<Token<'a>> {
     Lexer::new(input).map(|s| s.inner).collect()
@@ -67,6 +67,9 @@ fn test_numbers() {
         ("1e10", vec![Number("1e10")]),
         ("1.5e-3", vec![Number("1.5e-3")]),
         (".5", vec![Number(".5")]),
+        ("-.5", vec![Number("-.5")]),
+        ("+.5", vec![Number("+.5")]),
+        ("-.0", vec![Number("-.0")]),
     ];
     for (code, tokens) in cases {
         assert_eq!(tokenize(code), tokens);
@@ -149,6 +152,11 @@ fn test_ambiguous() {
         ("+foo", vec![Symbol("+foo")]),
         ("...", vec![Symbol("...")]),
         (".foo", vec![Symbol(".foo")]),
+        ("-.", vec![Symbol("-.")]),
+        ("+.", vec![Symbol("+.")]),
+        (".", vec![Symbol(".")]),
+        ("+.a", vec![Symbol("+.a")]),
+        ("-.a", vec![Symbol("-.a")]),
     ];
     for (code, tokens) in cases {
         assert_eq!(tokenize(code), tokens);
-- 
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