@@ -4,7 +4,7 @@ use crate::errors::{
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NoSyntaxVarsExprRepeat , VarStillRepeating ,
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} ;
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use crate :: mbe:: macro_parser:: { MatchedNonterminal , MatchedSeq , MatchedTokenTree , NamedMatch } ;
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- use crate :: mbe:: { self , MetaVarExpr } ;
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+ use crate :: mbe:: { self , KleeneOp , MetaVarExpr } ;
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use rustc_ast:: mut_visit:: { self , MutVisitor } ;
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use rustc_ast:: token:: { self , Delimiter , Token , TokenKind } ;
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use rustc_ast:: tokenstream:: { DelimSpacing , DelimSpan , Spacing , TokenStream , TokenTree } ;
@@ -42,6 +42,7 @@ enum Frame<'a> {
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tts : & ' a [ mbe:: TokenTree ] ,
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idx : usize ,
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sep : Option < Token > ,
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+ kleene_op : KleeneOp ,
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} ,
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}
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@@ -207,7 +208,7 @@ pub(super) fn transcribe<'a>(
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// Is the repetition empty?
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if len == 0 {
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- if seq. kleene . op == mbe :: KleeneOp :: OneOrMore {
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+ if seq. kleene . op == KleeneOp :: OneOrMore {
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// FIXME: this really ought to be caught at macro definition
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// time... It happens when the Kleene operator in the matcher and
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// the body for the same meta-variable do not match.
@@ -227,6 +228,7 @@ pub(super) fn transcribe<'a>(
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idx : 0 ,
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sep : seq. separator . clone ( ) ,
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tts : & delimited. tts ,
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+ kleene_op : seq. kleene . op ,
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} ) ;
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}
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}
@@ -243,7 +245,7 @@ pub(super) fn transcribe<'a>(
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MatchedTokenTree ( tt) => {
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// `tt`s are emitted into the output stream directly as "raw tokens",
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// without wrapping them into groups.
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- result. push ( tt . clone ( ) ) ;
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+ result. push ( maybe_use_metavar_location ( cx , & stack , sp , tt ) ) ;
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}
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MatchedNonterminal ( nt) => {
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// Other variables are emitted into the output stream as groups with
@@ -308,6 +310,62 @@ pub(super) fn transcribe<'a>(
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}
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}
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+ /// Usually metavariables `$var` produce interpolated tokens, which have an additional place for
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+ /// keeping both the original span and the metavariable span. For `tt` metavariables that's not the
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+ /// case however, and there's no place for keeping a second span. So we try to give the single
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+ /// produced span a location that would be most useful in practice (the hygiene part of the span
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+ /// must not be changed).
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+ ///
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+ /// Different locations are useful for different purposes:
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+ /// - The original location is useful when we need to report a diagnostic for the original token in
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+ /// isolation, without combining it with any surrounding tokens. This case occurs, but it is not
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+ /// very common in practice.
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+ /// - The metavariable location is useful when we need to somehow combine the token span with spans
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+ /// of its surrounding tokens. This is the most common way to use token spans.
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+ ///
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+ /// So this function replaces the original location with the metavariable location in all cases
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+ /// except these two:
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+ /// - The metavariable is an element of undelimited sequence `$($tt)*`.
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+ /// These are typically used for passing larger amounts of code, and tokens in that code usually
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+ /// combine with each other and not with tokens outside of the sequence.
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+ /// - The metavariable span comes from a different crate, then we prefer the more local span.
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+ ///
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+ /// FIXME: Find a way to keep both original and metavariable spans for all tokens without
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+ /// regressing compilation time too much. Several experiments for adding such spans were made in
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+ /// the past (PR #95580, #118517, #118671) and all showed some regressions.
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+ fn maybe_use_metavar_location (
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+ cx : & ExtCtxt < ' _ > ,
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+ stack : & [ Frame < ' _ > ] ,
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+ metavar_span : Span ,
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+ orig_tt : & TokenTree ,
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+ ) -> TokenTree {
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+ let undelimited_seq = matches ! (
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+ stack. last( ) ,
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+ Some ( Frame :: Sequence {
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+ tts: [ _] ,
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+ sep: None ,
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+ kleene_op: KleeneOp :: ZeroOrMore | KleeneOp :: OneOrMore ,
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+ ..
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+ } )
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+ ) ;
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+ if undelimited_seq || cx. source_map ( ) . is_imported ( metavar_span) {
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+ return orig_tt. clone ( ) ;
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+ }
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+
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+ match orig_tt {
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+ TokenTree :: Token ( Token { kind, span } , spacing) => {
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+ let span = metavar_span. with_ctxt ( span. ctxt ( ) ) ;
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+ TokenTree :: Token ( Token { kind : kind. clone ( ) , span } , * spacing)
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+ }
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+ TokenTree :: Delimited ( dspan, dspacing, delimiter, tts) => {
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+ let open = metavar_span. shrink_to_lo ( ) . with_ctxt ( dspan. open . ctxt ( ) ) ;
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+ let close = metavar_span. shrink_to_hi ( ) . with_ctxt ( dspan. close . ctxt ( ) ) ;
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+ let dspan = DelimSpan :: from_pair ( open, close) ;
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+ TokenTree :: Delimited ( dspan, * dspacing, * delimiter, tts. clone ( ) )
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+ }
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+ }
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+ }
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+
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/// Lookup the meta-var named `ident` and return the matched token tree from the invocation using
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/// the set of matches `interpolations`.
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///
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