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Commitdad9557

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Add unit tests forParser::look_ahead.
It's currently buggy, so some of the test results are surprising, asdescribed in the `FIXME` comments. The bugs will be fixed in subsequentcommits.
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‎compiler/rustc_parse/src/parser/tests.rs‎

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Original file line numberDiff line numberDiff line change
@@ -1376,6 +1376,122 @@ fn ttdelim_span() {
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});
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}
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// Uses a macro rather than a function so that failure messages mention the
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// correct line in the test function.
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macro_rules! look{
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($p:ident, $dist:literal, $kind:expr) =>{
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$p.look_ahead($dist, |tok| assert_eq!($kind, tok.kind));
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};
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}
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#[test]
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fnlook_ahead(){
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create_default_session_globals_then(||{
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let sym_f =Symbol::intern("f");
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let sym_x =Symbol::intern("x");
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#[allow(non_snake_case)]
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let sym_S =Symbol::intern("S");
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let raw_no =IdentIsRaw::No;
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let psess =psess();
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letmut p =string_to_parser(&psess,"fn f(x: u32) { x } struct S;".to_string());
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// Current position is the `fn`.
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look!(p,0, token::Ident(kw::Fn, raw_no));
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look!(p,1, token::Ident(sym_f, raw_no));
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look!(p,2, token::OpenDelim(Delimiter::Parenthesis));
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look!(p,3, token::Ident(sym_x, raw_no));
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look!(p,4, token::Colon);
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look!(p,5, token::Ident(sym::u32, raw_no));
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look!(p,6, token::CloseDelim(Delimiter::Parenthesis));
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look!(p,7, token::OpenDelim(Delimiter::Brace));
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look!(p,8, token::Ident(sym_x, raw_no));
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look!(p,9, token::CloseDelim(Delimiter::Brace));
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look!(p,10, token::Ident(kw::Struct, raw_no));
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look!(p,11, token::Ident(sym_S, raw_no));
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look!(p,12, token::Semi);
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// Any lookahead past the end of the token stream returns `Eof`.
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look!(p,13, token::Eof);
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look!(p,14, token::Eof);
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look!(p,15, token::Eof);
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look!(p,100, token::Eof);
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// Move forward to the first `x`.
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for _in0..3{
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p.bump();
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}
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look!(p,0, token::Ident(sym_x, raw_no));
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look!(p,1, token::Colon);
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look!(p,2, token::Ident(sym::u32, raw_no));
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look!(p,3, token::CloseDelim(Delimiter::Parenthesis));
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// FIXME(nnethercote) If we lookahead any distance past a close delim
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// we currently return that close delim.
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look!(p,4, token::CloseDelim(Delimiter::Parenthesis));
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look!(p,5, token::CloseDelim(Delimiter::Parenthesis));
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look!(p,6, token::CloseDelim(Delimiter::Parenthesis));
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look!(p,100, token::CloseDelim(Delimiter::Parenthesis));
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// Move forward to the `;`.
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for _in0..9{
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p.bump();
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}
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look!(p,0, token::Semi);
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// Any lookahead past the end of the token stream returns `Eof`.
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look!(p,1, token::Eof);
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look!(p,100, token::Eof);
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// Move one past the `;`, i.e. past the end of the token stream.
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p.bump();
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look!(p,0, token::Eof);
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look!(p,1, token::Eof);
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look!(p,100, token::Eof);
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// Bumping after Eof is idempotent.
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p.bump();
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look!(p,0, token::Eof);
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look!(p,1, token::Eof);
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look!(p,100, token::Eof);
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});
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}
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/// FIXME(nnethercote) Currently there is some buggy behaviour when using
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/// `look_ahead` not within the outermost token stream, as this test shows.
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#[test]
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fnlook_ahead_non_outermost_stream(){
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create_default_session_globals_then(||{
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let sym_f =Symbol::intern("f");
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#[allow(non_snake_case)]
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let sym_S =Symbol::intern("S");
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let raw_no =IdentIsRaw::No;
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let psess =psess();
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letmut p =string_to_parser(&psess,"mod m { fn f(x: u32) { x } struct S; }".to_string());
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// Move forward to the `fn`, which is not within the outermost token
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// stream (because it's inside the `mod { ... }`).
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for _in0..3{
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p.bump();
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}
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look!(p,0, token::Ident(kw::Fn, raw_no));
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look!(p,1, token::Ident(sym_f, raw_no));
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look!(p,2, token::OpenDelim(Delimiter::Parenthesis));
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// FIXME(nnethercote) The current code incorrectly skips the `x: u32)`
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// to the next token tree.
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look!(p,3, token::OpenDelim(Delimiter::Brace));
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// FIXME(nnethercote) The current code incorrectly skips the `x }`
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// to the next token tree.
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look!(p,4, token::Ident(kw::Struct, raw_no));
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look!(p,5, token::Ident(sym_S, raw_no));
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look!(p,6, token::Semi);
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// FIXME(nnethercote) If we lookahead any distance past a close delim
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// we currently return that close delim.
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look!(p,7, token::CloseDelim(Delimiter::Brace));
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look!(p,8, token::CloseDelim(Delimiter::Brace));
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look!(p,9, token::CloseDelim(Delimiter::Brace));
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look!(p,100, token::CloseDelim(Delimiter::Brace));
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});
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}
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// This tests that when parsing a string (rather than a file) we don't try
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// and read in a file for a module declaration and just parse a stub.
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// See `recurse_into_file_modules` in the parser.

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