Catch small edge-case in parser

worldedit-core/src/main/antlr/com/sk89q/worldedit/antlr/Expression.g4

@@ -63,7 +63,7 @@ fragment EXP_CHAR : [eE] ;
 fragment DECIMAL : '.' DIGIT+ ( EXP_CHAR SIGN? DIGIT+ )? ;
 
 // All numbers are treated the same. No int/dec divide.
-NUMBER : SIGN? ( DIGIT+ DECIMAL? | DECIMAL ) ;
+NUMBER : ( DIGIT+ DECIMAL? | DECIMAL ) ;
 
 ID : [A-Za-z] [0-9A-Za-z_]* ;
 

worldedit-core/src/test/java/com/sk89q/worldedit/internal/expression/ExpressionTest.java

@@ -74,6 +74,11 @@ public class ExpressionTest {
         assertEquals(8, compile("foo+bar", "foo", "bar").evaluate(5D, 3D), 0);
     }
 
+    @Test
+    void testTightTokenization() {
+        assertEquals(4, simpleEval("3+1"), 0);
+    }
+
     @Test
     public void testErrors() {
         // test lexer errors