compiletest: extend syntax with support for choosing same line as previous line.

Author: pnkfelix

src/compiletest/errors.rs

@@ -7,6 +7,7 @@
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
+use self::WhichLine::*;
 
 use std::ascii::AsciiExt;
 use std::io::{BufferedReader, File};
@@ -18,28 +19,74 @@ pub struct ExpectedError {
     pub msg: String,
 }
 
-pub static EXPECTED_PATTERN : &'static str = r"//~(?P<adjusts>\^*)\s*(?P<kind>\S*)\s*(?P<msg>.*)";
+/// Looks for either "//~| KIND MESSAGE" or "//~^^... KIND MESSAGE"
+/// The former is a "follow" that inherits its target from the preceding line;
+/// the latter is an "adjusts" that goes that many lines up.
+///
+/// Goal is to enable tests both like: //~^^^ ERROR go up three
+/// and also //~^ ERROR message one for the preceding line, and
+///          //~| ERROR message two for that same line.
+
+pub static EXPECTED_PATTERN : &'static str =
+    r"//~(?P<follow>\|)?(?P<adjusts>\^*)\s*(?P<kind>\S*)\s*(?P<msg>.*)";
+
+#[deriving(PartialEq, Show)]
+enum WhichLine { ThisLine, FollowPrevious(uint), AdjustBackward(uint) }
 
 // Load any test directives embedded in the file
 pub fn load_errors(re: &Regex, testfile: &Path) -> Vec<ExpectedError> {
     let mut rdr = BufferedReader::new(File::open(testfile).unwrap());
 
+    // `last_nonfollow_error` tracks the most recently seen
+    // line with an error template that did not use the
+    // follow-syntax, "//~| ...".
+    //
+    // (pnkfelix could not find an easy way to compose Iterator::scan
+    // and Iterator::filter_map to pass along this information into
+    // `parse_expected`. So instead I am storing that state here and
+    // updating it in the map callback below.)
+    let mut last_nonfollow_error = None;
+
     rdr.lines().enumerate().filter_map(|(line_no, ln)| {
-        parse_expected(line_no + 1, ln.unwrap().as_slice(), re)
+        parse_expected(last_nonfollow_error,
+                       line_no + 1,
+                       ln.unwrap().as_slice(), re)
+            .map(|(which, error)| {
+                match which {
+                    FollowPrevious(_) => {}
+                    _ => last_nonfollow_error = Some(error.line),
+                }
+                error
+            })
     }).collect()
 }
 
-fn parse_expected(line_num: uint, line: &str, re: &Regex) -> Option<ExpectedError> {
+fn parse_expected(last_nonfollow_error: Option<uint>,
+                  line_num: uint,
+                  line: &str,
+                  re: &Regex) -> Option<(WhichLine, ExpectedError)> {
     re.captures(line).and_then(|caps| {
         let adjusts = caps.name("adjusts").len();
         let kind = caps.name("kind").to_ascii_lower();
         let msg = caps.name("msg").trim().to_string();
+        let follow = caps.name("follow").len() > 0;
+
+        let (which, line) = if follow {
+            assert!(adjusts == 0, "use either //~| or //~^, not both.");
+            let line = last_nonfollow_error.unwrap_or_else(|| {
+                panic!("encountered //~| without preceding //~^ line.")
+            });
+            (FollowPrevious(line), line)
+        } else {
+            let which =
+                if adjusts > 0 { AdjustBackward(adjusts) } else { ThisLine };
+            let line = line_num - adjusts;
+            (which, line)
+        };
 
-        debug!("line={} kind={} msg={}", line_num, kind, msg);
-        Some(ExpectedError {
-            line: line_num - adjusts,
-            kind: kind,
-            msg: msg,
-        })
+        debug!("line={} which={} kind={} msg={}", line_num, which, kind, msg);
+        Some((which, ExpectedError { line: line,
+                                     kind: kind,
+                                     msg: msg, }))
     })
 }