Implement underscore variable unchecked when unused.

src/node_arr/node_arr.rs

@@ -162,7 +162,13 @@ impl NodeArr {
                                     &mut uv,
                                 );
                                 n = simplified::exec(n);
-                                let v = Var::new(_s, n);
+                                let v = match _s.as_bytes()[0] {
+                                    b'_' => Var::mnew(_s, n),
+                                    _ => Var::new(_s, n),
+                                };
+                                if v.m {
+                                    uv.push(v.to_owned().s);
+                                }
                                 l.push(v);
                             }
                         }

src/program/program.rs

@@ -90,7 +90,13 @@ impl Program {
                                 let mut n =
                                     beta(&mut n.to_owned().rhs.unwrap().to_owned(), ev, &mut uv);
                                 n = simplified::exec(n);
-                                let v = Var::new(_s, n);
+                                let v = match _s.as_bytes()[0] {
+                                    b'_' => Var::mnew(_s, n),
+                                    _ => Var::new(_s, n),
+                                };
+                                if v.m {
+                                    uv.push(v.to_owned().s);
+                                }
                                 g.push(v);
                             }
                         }

src/tests/parser/tests.rs

@@ -7,6 +7,8 @@ use super::super::super::node_arr::node_arr::*;
 #[cfg(test)]
 use super::super::super::parser::error::*;
 #[cfg(test)]
+use super::super::super::program::program::*;
+#[cfg(test)]
 use super::super::super::token::token::*;
 
 #[test]
@@ -268,3 +270,23 @@ fn eof_around_closed_else_stmt_test() {
     };
     assert!(n)
 }
+
+// #[test]
+// fn unused_variable_check_for_under_score_grobal_variable() {
+//     let t = Token::tokenize("int _g = 10; fn { _ }").unwrap();
+//     let n = match Program::w_parser(t) {
+//         Ok(_) => true,
+//         Err(_) => false,
+//     };
+//     assert!(n)
+// }
+
+#[test]
+fn unused_variable_check_for_under_score_local_variable() {
+    let t = Token::tokenize("fn { int _g = 10; _ }").unwrap();
+    let n = match Program::w_parser(t) {
+        Ok(_) => true,
+        Err(_) => false,
+    };
+    assert!(n)
+}

test.sh

@@ -79,6 +79,9 @@ assert 0 'int g = 2; fn { int v = 4; 1+v*g/4-1; _ }' simplified
 assert 10 'int g = 2; int l = 3; int o = 4; fn int { int v = 4; l+v*o/g-1; }' simplified
 assert 0 'int g = 2; int l = 3; int o = 4; fn { int v = 4; l+v*o/g-1; _ }'
 assert 3 'int g = 10; fn int { g; int g = 3; g }'
+assert 0 'int _g = 10; fn { _ }'
+assert 0 'fn { int _u = 8; _ }'
+assert 16 'fn int { int _u = 8; int a = 2; a*_u }'
 
 echo "------------------------------"
 echo "All test passed!"