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cleanup shebang handling in the lexer #59687

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Apr 5, 2019
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cleanup shebang handling in the lexer #59687

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16 changes: 5 additions & 11 deletions src/libsyntax/parse/lexer/mod.rs
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Original file line number Diff line number Diff line change
@@ -1,10 +1,9 @@
use crate::ast::{self, Ident};
use crate::source_map::{SourceMap, FilePathMapping};
use crate::parse::{token, ParseSess};
use crate::symbol::Symbol;

use errors::{Applicability, FatalError, Diagnostic, DiagnosticBuilder};
use syntax_pos::{BytePos, CharPos, Pos, Span, NO_EXPANSION};
use syntax_pos::{BytePos, Pos, Span, NO_EXPANSION};
use core::unicode::property::Pattern_White_Space;

use std::borrow::Cow;
Expand Down Expand Up @@ -667,14 +666,9 @@ impl<'a> StringReader<'a> {
return None;
}

// I guess this is the only way to figure out if
// we're at the beginning of the file...
let smap = SourceMap::new(FilePathMapping::empty());
smap.files.borrow_mut().source_files.push(self.source_file.clone());
let loc = smap.lookup_char_pos_adj(self.pos);
debug!("Skipping a shebang");
if loc.line == 1 && loc.col == CharPos(0) {
// FIXME: Add shebang "token", return it
let is_beginning_of_file = self.pos == self.source_file.start_pos;
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So, the new code accepts shebang at the start of anything that compiler treats as a source file - out-of-line mod, perhaps command line or macro?
And I'm not even sure what the old code does.
I rather wish this thing never existed in the language.

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My reading is that the old code did the same, but in a more elaborate way, by binary searching in a single-element slice. I’ve manually checked that shebangs are accepted in the outofline modules today.

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For the referrnce, here’s the original commit that added the code: #2430

Accidentally, it also added this _adj function, which I would like to get rid of next

if is_beginning_of_file {
debug!("Skipping a shebang");
let start = self.pos;
while !self.ch_is('\n') && !self.is_eof() {
self.bump();
Expand Down Expand Up @@ -1911,7 +1905,7 @@ mod tests {

use crate::ast::{Ident, CrateConfig};
use crate::symbol::Symbol;
use crate::source_map::SourceMap;
use crate::source_map::{SourceMap, FilePathMapping};
use crate::feature_gate::UnstableFeatures;
use crate::parse::token;
use crate::diagnostics::plugin::ErrorMap;
Expand Down