Allow error comments above the error site.

CHANGELOG.md

@@ -9,7 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-### Fixedw
+* Add `//~v` comments to put an error matcher above the error site.
+
+### Fixed
 
 ### Changed
 

src/parser.rs

@@ -280,7 +280,9 @@ impl Comments {
         let defaults = std::mem::take(parser.comments.revisioned.get_mut(&[][..]).unwrap());
 
         let mut fallthrough_to = None; // The line that a `|` will refer to.
+        let mut last_line = 0;
         for (l, line) in content.as_ref().lines().enumerate() {
+            last_line = l + 1;
             let l = NonZeroUsize::new(l + 1).unwrap(); // enumerate starts at 0, but line numbers start at 1
             let span = Span {
                 file: file.to_path_buf(),
@@ -316,6 +318,25 @@ impl Comments {
             }
         }
 
+        for revisioned in parser.comments.revisioned.values() {
+            for m in &revisioned.error_matches {
+                if m.line.get() > last_line {
+                    let span = match &m.kind {
+                        ErrorMatchKind::Pattern { pattern, .. } => pattern.span(),
+                        ErrorMatchKind::Code(code) => code.span(),
+                    };
+                    parser.errors.push(Error::InvalidComment {
+                        msg: format!(
+                            "//~v pattern is trying to refer to line {}, but the file only has {} lines",
+                            m.line.get(),
+                            last_line,
+                        ),
+                        span,
+                    });
+                }
+            }
+        }
+
         let Revisioned {
             span,
             ignore,
@@ -852,6 +873,30 @@ impl CommentParser<&mut Revisioned> {
                     }
                 }
             }
+            Some(Spanned {
+                content: 'v',
+                span: _,
+            }) => {
+                let offset = pattern.chars().take_while(|c| c.content == 'v').count();
+                match pattern
+                    .span()
+                    .line_start
+                    .get()
+                    .checked_add(offset)
+                    .and_then(NonZeroUsize::new)
+                {
+                    Some(match_line) => (match_line, pattern.split_at(offset).1),
+                    _ => {
+                        // The line count of the file is not yet known so we can only check
+                        // if the resulting line is in the range of a usize.
+                        self.error(pattern.span(), format!(
+                            "//~v pattern is trying to refer to {} lines below, which is more than ui_test can count",
+                            offset,
+                        ));
+                        return;
+                    }
+                }
+            }
             Some(_) => (pattern.span().line_start, pattern),
             None => {
                 self.error(pattern.span(), "no pattern specified");

tests/integrations/basic-fail/Cargo.stdout

@@ -12,6 +12,7 @@ tests/actual_tests/filters.rs ... FAILED
 tests/actual_tests/foomp.rs ... FAILED
 tests/actual_tests/foomp2.rs ... FAILED
 tests/actual_tests/pattern_too_many_arrow.rs ... FAILED
+tests/actual_tests/pattern_too_many_arrow_above.rs ... FAILED
 tests/actual_tests/rustc_ice.rs ... FAILED
 
 FAILED TEST: tests/actual_tests/bad_pattern.rs
@@ -268,6 +269,22 @@ full stdout:
 
 
 
+FAILED TEST: tests/actual_tests/pattern_too_many_arrow_above.rs
+command: "parse comments"
+
+error: //~v pattern is trying to refer to line 8, but the file only has 6 lines
+ --> tests/actual_tests/pattern_too_many_arrow_above.rs:2:22
+  |
+2 |     //~vvvvvv ERROR: mismatched types
+  |                      ^^^^^^^^^^^^^^^^
+  |
+
+full stderr:
+
+full stdout:
+
+
+
 FAILED TEST: tests/actual_tests/rustc_ice.rs
 command: "rustc" "--error-format=json" "--extern" "basic_fail=$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug/libbasic_fail.rlib" "--extern" "basic_fail=$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug/libbasic_fail-$HASH.rmeta" "-L" "$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug" "-L" "$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug" "--out-dir" "$TMP "tests/actual_tests/rustc_ice.rs" "-Ztreat-err-as-bug" "--edition" "2021"
 
@@ -323,9 +340,10 @@ FAILURES:
     tests/actual_tests/foomp.rs
     tests/actual_tests/foomp2.rs
     tests/actual_tests/pattern_too_many_arrow.rs
+    tests/actual_tests/pattern_too_many_arrow_above.rs
     tests/actual_tests/rustc_ice.rs
 
-test result: FAIL. 9 failed;
+test result: FAIL. 10 failed;
 
 Building dependencies ... ok
 tests/actual_tests_bless/aux_build_not_found.rs ... FAILED
@@ -914,6 +932,7 @@ tests/actual_tests/filters.rs ... FAILED
 tests/actual_tests/foomp.rs ... FAILED
 tests/actual_tests/foomp2.rs ... FAILED
 tests/actual_tests/pattern_too_many_arrow.rs ... FAILED
+tests/actual_tests/pattern_too_many_arrow_above.rs ... FAILED
 tests/actual_tests/rustc_ice.rs ... FAILED
 
 FAILED TEST: tests/actual_tests/bad_pattern.rs
@@ -1002,6 +1021,22 @@ full stdout:
 
 
 
+FAILED TEST: tests/actual_tests/pattern_too_many_arrow_above.rs
+command: "parse comments"
+
+error: //~v pattern is trying to refer to line 8, but the file only has 6 lines
+ --> tests/actual_tests/pattern_too_many_arrow_above.rs:2:22
+  |
+2 |     //~vvvvvv ERROR: mismatched types
+  |                      ^^^^^^^^^^^^^^^^
+  |
+
+full stderr:
+
+full stdout:
+
+
+
 FAILED TEST: tests/actual_tests/rustc_ice.rs
 command: "$CMD" "tests/actual_tests/rustc_ice.rs" "-Ztreat-err-as-bug" "--edition" "2021"
 
@@ -1019,9 +1054,10 @@ FAILURES:
     tests/actual_tests/foomp.rs
     tests/actual_tests/foomp2.rs
     tests/actual_tests/pattern_too_many_arrow.rs
+    tests/actual_tests/pattern_too_many_arrow_above.rs
     tests/actual_tests/rustc_ice.rs
 
-test result: FAIL. 9 failed;
+test result: FAIL. 10 failed;
 
 
 running 0 tests

tests/integrations/basic-fail/tests/actual_tests/pattern_too_many_arrow_above.rs

@@ -0,0 +1,6 @@
+fn main() {
+    //~vvvvvv ERROR: mismatched types
+    use_unit(1_u32);
+}
+
+fn use_unit(_: ()) {}

tests/integrations/basic/Cargo.stdout

@@ -13,6 +13,7 @@ Building aux file tests/actual_tests/auxiliary/derive_proc_macro.rs ... ok
 tests/actual_tests/aux_derive.rs ... ok
 Building aux file tests/actual_tests/auxiliary/the_proc_macro.rs ... ok
 tests/actual_tests/aux_proc_macro.rs ... ok
+tests/actual_tests/error_above.rs ... ok
 tests/actual_tests/executable.rs ... ok
 tests/actual_tests/foomp-rustfix.rs ... ok
 tests/actual_tests/foomp.rs ... ok
@@ -23,7 +24,7 @@ tests/actual_tests/unicode.rs ... ok
 tests/actual_tests/windows_paths.rs ... ok
 tests/actual_tests/subdir/aux_proc_macro.rs ... ok
 
-test result: ok. 11 passed;
+test result: ok. 12 passed;
 
 
 running 0 tests

tests/integrations/basic/tests/actual_tests/error_above.rs

@@ -0,0 +1,6 @@
+use basic::add;
+
+fn main() {
+    //~v ERROR: mismatched types
+    add("42", 3);
+}

tests/integrations/basic/tests/actual_tests/error_above.stderr

@@ -0,0 +1,17 @@
+error[E0308]: mismatched types
+ --> tests/actual_tests/error_above.rs:5:9
+  |
+5 |     add("42", 3);
+  |     --- ^^^^ expected `usize`, found `&str`
+  |     |
+  |     arguments to this function are incorrect
+  |
+note: function defined here
+ --> $DIR/tests/integrations/basic/src/lib.rs:1:8
+  |
+1 | pub fn add(left: usize, right: usize) -> usize {
+  |        ^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.