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Clarify space_between
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To avoid `!matches!(...)`, which is hard to think about. Instead every case now uses direct pattern matching and returns true or false. Also add a couple of cases to the `stringify.rs` test that currently print badly.
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@ -146,37 +146,49 @@ pub fn print_crate<'a>(
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s.s.eof()
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}
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/// This makes printed token streams look slightly nicer,
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/// and also addresses some specific regressions described in #63896 and #73345.
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fn space_between(prev: &TokenTree, curr: &TokenTree) -> bool {
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if let TokenTree::Token(token, _) = prev {
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// No space after these tokens, e.g. `x.y`, `$e`
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// (The carets point to `prev`.) ^ ^
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if matches!(token.kind, token::Dot | token::Dollar) {
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return false;
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}
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if let token::DocComment(comment_kind, ..) = token.kind {
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return comment_kind != CommentKind::Line;
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}
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}
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match curr {
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// No space before these tokens, e.g. `foo,`, `println!`, `x.y`
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// (The carets point to `curr`.) ^ ^ ^
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/// Should two consecutive tokens be printed with a space between them?
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///
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/// Note: some old proc macros parse pretty-printed output, so changes here can
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/// break old code. For example:
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/// - #63896: `#[allow(unused,` must be printed rather than `#[allow(unused ,`
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/// - #73345: `#[allow(unused)] must be printed rather than `# [allow(unused)]
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///
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fn space_between(tt1: &TokenTree, tt2: &TokenTree) -> bool {
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use token::*;
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use Delimiter::*;
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use TokenTree::Delimited as Del;
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use TokenTree::Token as Tok;
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// Each match arm has one or more examples in comments. The default is to
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// insert space between adjacent tokens, except for the cases listed in
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// this match.
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match (tt1, tt2) {
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// No space after line doc comments.
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(Tok(Token { kind: DocComment(CommentKind::Line, ..), .. }, _), _) => false,
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// `.` + ANYTHING: `x.y`, `tup.0`
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// `$` + ANYTHING: `$e`
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(Tok(Token { kind: Dot | Dollar, .. }, _), _) => false,
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// ANYTHING + `,`: `foo,`
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// ANYTHING + `.`: `x.y`, `tup.0`
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// ANYTHING + `!`: `foo! { ... }`
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//
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// FIXME: having `Not` here works well for macro invocations like
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// `println!()`, but is bad when `!` means "logical not" or "the never
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// type", where the lack of space causes ugliness like this:
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// `Fn() ->!`, `x =! y`, `if! x { f(); }`.
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TokenTree::Token(token, _) => !matches!(token.kind, token::Comma | token::Not | token::Dot),
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// No space before parentheses if preceded by these tokens, e.g. `foo(...)`
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TokenTree::Delimited(_, Delimiter::Parenthesis, _) => {
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!matches!(prev, TokenTree::Token(Token { kind: token::Ident(..), .. }, _))
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}
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// No space before brackets if preceded by these tokens, e.g. `#[...]`
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TokenTree::Delimited(_, Delimiter::Bracket, _) => {
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!matches!(prev, TokenTree::Token(Token { kind: token::Pound, .. }, _))
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}
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TokenTree::Delimited(..) => true,
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// FIXME: Incorrect cases:
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// - Logical not: `x =! y`, `if! x { f(); }`
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// - Never type: `Fn() ->!`
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(_, Tok(Token { kind: Comma | Dot | Not, .. }, _)) => false,
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// IDENT + `(`: `f(3)`
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//
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// FIXME: Incorrect cases:
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// - Let: `let(a, b) = (1, 2)`
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(Tok(Token { kind: Ident(..), .. }, _), Del(_, Parenthesis, _)) => false,
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// `#` + `[`: `#[attr]`
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(Tok(Token { kind: Pound, .. }, _), Del(_, Bracket, _)) => false,
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_ => true,
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}
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}
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@ -115,6 +115,7 @@ fn test_expr() {
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"a + b * c - d + -1 * -2 - -3",
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"a + b * c - d + - 1 * - 2 - - 3"
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);
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c2!(expr, [ x = !y ], "x = !y", "x =! y"); // FIXME
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// ExprKind::Unary
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c2!(expr, [ *expr ], "*expr", "* expr");
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@ -137,6 +138,7 @@ fn test_expr() {
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// ExprKind::If
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c1!(expr, [ if true {} ], "if true {}");
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c2!(expr, [ if !true {} ], "if !true {}", "if! true {}"); // FIXME
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c2!(expr,
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[ if ::std::blah() { } else { } ],
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"if ::std::blah() {} else {}",
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