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Collapse bare ExpectedExpression to 'invalid syntax'; fix '<>' diagnostic offset #8540

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Merged
youknowone merged 2 commits into from
Aug 19, 2026
+36 −2
Merged

Collapse bare ExpectedExpression to 'invalid syntax'; fix '<>' diagnostic offset #8540

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97f53b8
Collapse bare ExpectedExpression to 'invalid syntax'; fix '<>' diagno…
mumallaeng Aug 17, 2026
42900dc
Require an adjacent '>' before treating '<' as the obsolete <> operator
mumallaeng Aug 19, 2026
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2 changes: 0 additions & 2 deletions Lib/test/test_flufl.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,6 @@ def test_barry_as_bdfl(self):
# parser reports the start of the token
self.assertEqual(cm.exception.offset, 3)

@unittest.expectedFailure # TODO: RUSTPYTHON
def test_guido_as_bdfl(self):
code = '2 {0} 3'
compile(code.format('!='), '<BDFL test>', 'exec')
Expand Down Expand Up @@ -50,7 +49,6 @@ def test_barry_as_bdfl_look_ma_with_no_compiler_flags(self):
self.assertEqual(cm.exception.lineno, 1)
self.assertEqual(cm.exception.offset, len(code) - 4)

@unittest.expectedFailure # TODO: RUSTPYTHON
def test_barry_as_bdfl_relative_import(self):
code = "from .__future__ import barry_as_FLUFL;2 {0} 3"
compile(code.format('!='), '<FLUFL test>', 'exec')
Expand Down
36 changes: 36 additions & 0 deletions crates/compiler/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -362,9 +362,45 @@ fn cpython_parse_diagnostic_override(
));
}

// `2 <> 3` outside Barry mode: ruff lexes `<` then an unexpected `>` and
// reports `ExpectedExpression` starting at the `>`. CPython's tokenizer
// treats `<>` as a single obsolete token and points at its start (the
// `<`) instead, so shift the reported location back over it.
source_error!(barry_flufl_obsolete_operator_error(error, source_text));

// CPython's PEG parser collapses a bare "expected an expression" failure
// into the generic "invalid syntax" message. rustpython-vm's `vm_new.rs`
// does this same collapse for its own callers; rustpython-compiler has no
// vm dependency, so mirror it here.
if matches!(&error.error, parser::ParseErrorType::ExpectedExpression) {
let (loc, end_loc) = adjusted_error_locations(source_file, error.location);
return Some(NormalizedParseDiagnostic::new(
parser::ParseErrorType::OtherError("invalid syntax".into()),
loc,
end_loc,
));
}

None
}

fn barry_flufl_obsolete_operator_error(
error: &parser::ParseError,
source: &str,
) -> Option<(String, usize, usize)> {
if !matches!(&error.error, parser::ParseErrorType::ExpectedExpression) {
return None;
}
let start = error.location.start().to_usize();
if start == 0 || source.as_bytes().get(start - 1) != Some(&b'<') {
return None;
}
if source.as_bytes().get(start) != Some(&b'>') {
return None;
}
Some(("invalid syntax".to_string(), start - 1, start + 1))
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}

fn eof_parse_diagnostic(
error: &parser::ParseError,
source_file: &SourceFile,
Expand Down
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