ppTests Avoid removal of undef and undefineall directives.

- Similarly to how `define is left in-place, `undef and `undefine are also
  left in-place.
- Corresponding fixes to macro_LINE and macro_FILE.
- These directives were not in any testcases before this branch.

sv-parser-pp/src/preprocess.rs

@@ -379,18 +379,28 @@ pub fn preprocess_str<T: AsRef<Path>, U: AsRef<Path>, V: BuildHasher>(
                 skip_whitespace = false;
             }
             NodeEvent::Enter(RefNode::UndefineCompilerDirective(x)) => {
-                skip_nodes.push(x.into());
-                skip = true;
-
                 let (_, _, ref name) = x.nodes;
                 let id = identifier((&name.nodes.0).into(), &s).unwrap();
                 defines.remove(&id);
+
+                let locate: Locate = x.try_into().unwrap();
+                let range = Range::new(locate.offset, locate.offset + locate.len);
+                ret.push(locate.str(&s), Some((path.as_ref(), range)));
+                skip_whitespace = true;
+            }
+            NodeEvent::Leave(RefNode::UndefineCompilerDirective(_)) => {
+                skip_whitespace = false;
             }
             NodeEvent::Enter(RefNode::UndefineallCompilerDirective(x)) => {
-                skip_nodes.push(x.into());
-                skip = true;
-
                 defines.clear();
+
+                let locate: Locate = x.try_into().unwrap();
+                let range = Range::new(locate.offset, locate.offset + locate.len);
+                ret.push(locate.str(&s), Some((path.as_ref(), range)));
+                skip_whitespace = true;
+            }
+            NodeEvent::Leave(RefNode::UndefineallCompilerDirective(_)) => {
+                skip_whitespace = false;
             }
             NodeEvent::Enter(RefNode::IfdefDirective(x)) => {
                 let (_, ref keyword, ref ifid, ref ifbody, ref elsif, ref elsebody, _, _) = x.nodes;

sv-parser-pp/testcases/expected/macro_FILE.sv

@@ -10,4 +10,6 @@
 `define __FILE__ "FOO"
 
 // The following undef should have no effect.
+`undef __FILE__
+
 // NOTE: Comparison against expected value are destined to fail in testcase.

sv-parser-pp/testcases/expected/macro_LINE.sv

@@ -10,6 +10,8 @@
 `define __LINE__ -2
 
 // The following undef should have no effect.
+`undef __LINE__
+
 module M;
   initial
     if (26 == 28)      // Should be "26 == 28".