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Remove pretty-print/reparse hack, and add derive-specific hack

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Aaron Hill 2020-11-23 01:43:55 -05:00
parent 2987785df3
commit 530a629635
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8 changed files with 186 additions and 410 deletions
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390
compiler/rustc_parse/src/lib.rs
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@ -7,22 +7,18 @@
use rustc_ast as ast;
use rustc_ast::attr::HasAttrs;
use rustc_ast::token::{self, DelimToken, Nonterminal, Token, TokenKind};
use rustc_ast::tokenstream::{self, LazyTokenStream, TokenStream, TokenTree};
use rustc_ast::token::{self, Nonterminal};
use rustc_ast::tokenstream::{self, CanSynthesizeMissingTokens, LazyTokenStream, TokenStream};
use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::sync::Lrc;
use rustc_errors::{Diagnostic, FatalError, Level, PResult};
use rustc_session::parse::ParseSess;
use rustc_span::{symbol::kw, FileName, SourceFile, Span, DUMMY_SP};
use rustc_span::{FileName, SourceFile, Span};
use smallvec::SmallVec;
use std::cell::RefCell;
use std::mem;
use std::path::Path;
use std::str;
use tracing::{debug, info};
use tracing::debug;
pub const MACRO_ARGUMENTS: Option<&str> = Some("macro arguments");
@ -237,7 +233,12 @@ pub fn parse_in<'a, T>(
// NOTE(Centril): The following probably shouldn't be here but it acknowledges the
// fact that architecturally, we are using parsing (read on below to understand why).
pub fn nt_to_tokenstream(nt: &Nonterminal, sess: &ParseSess, span: Span) -> TokenStream {
pub fn nt_to_tokenstream(
nt: &Nonterminal,
sess: &ParseSess,
span: Span,
synthesize_tokens: CanSynthesizeMissingTokens,
) -> TokenStream {
// A `Nonterminal` is often a parsed AST item. At this point we now
// need to convert the parsed AST to an actual token stream, e.g.
// un-parse it basically.
@ -255,9 +256,11 @@ pub fn nt_to_tokenstream(nt: &Nonterminal, sess: &ParseSess, span: Span) -> Toke
|tokens: Option<&LazyTokenStream>| tokens.as_ref().map(|t| t.create_token_stream());
let tokens = match *nt {
Nonterminal::NtItem(ref item) => prepend_attrs(&item.attrs, item.tokens.as_ref()),
Nonterminal::NtItem(ref item) => {
prepend_attrs(sess, &item.attrs, nt, span, item.tokens.as_ref())
}
Nonterminal::NtBlock(ref block) => convert_tokens(block.tokens.as_ref()),
Nonterminal::NtStmt(ref stmt) => prepend_attrs(stmt.attrs(), stmt.tokens()),
Nonterminal::NtStmt(ref stmt) => prepend_attrs(sess, stmt.attrs(), nt, span, stmt.tokens()),
Nonterminal::NtPat(ref pat) => convert_tokens(pat.tokens.as_ref()),
Nonterminal::NtTy(ref ty) => convert_tokens(ty.tokens.as_ref()),
Nonterminal::NtIdent(ident, is_raw) => {
@ -274,376 +277,45 @@ pub fn nt_to_tokenstream(nt: &Nonterminal, sess: &ParseSess, span: Span) -> Toke
if expr.tokens.is_none() {
debug!("missing tokens for expr {:?}", expr);
}
prepend_attrs(&expr.attrs, expr.tokens.as_ref())
prepend_attrs(sess, &expr.attrs, nt, span, expr.tokens.as_ref())
}
};
// Caches the stringification of 'good' `TokenStreams` which passed
// `tokenstream_probably_equal_for_proc_macro`. This allows us to avoid
// repeatedly stringifying and comparing the same `TokenStream` for deeply
// nested nonterminals.
//
// We cache by the strinification instead of the `TokenStream` to avoid
// needing to implement `Hash` for `TokenStream`. Note that it's possible to
// have two distinct `TokenStream`s that stringify to the same result
// (e.g. if they differ only in hygiene information). However, any
// information lost during the stringification process is also intentionally
// ignored by `tokenstream_probably_equal_for_proc_macro`, so it's fine
// that a single cache entry may 'map' to multiple distinct `TokenStream`s.
//
// This is a temporary hack to prevent compilation blowup on certain inputs.
// The entire pretty-print/retokenize process will be removed soon.
thread_local! {
static GOOD_TOKEN_CACHE: RefCell<FxHashSet<String>> = Default::default();
}
// FIXME(#43081): Avoid this pretty-print + reparse hack
// Pretty-print the AST struct without inserting any parenthesis
// beyond those explicitly written by the user (e.g. `ExpnKind::Paren`).
// The resulting stream may have incorrect precedence, but it's only
// ever used for a comparison against the capture tokenstream.
let source = pprust::nonterminal_to_string_no_extra_parens(nt);
let filename = FileName::macro_expansion_source_code(&source);
let reparsed_tokens = parse_stream_from_source_str(filename, source.clone(), sess, Some(span));
// During early phases of the compiler the AST could get modified
// directly (e.g., attributes added or removed) and the internal cache
// of tokens my not be invalidated or updated. Consequently if the
// "lossless" token stream disagrees with our actual stringification
// (which has historically been much more battle-tested) then we go
// with the lossy stream anyway (losing span information).
//
// Note that the comparison isn't `==` here to avoid comparing spans,
// but it *also* is a "probable" equality which is a pretty weird
// definition. We mostly want to catch actual changes to the AST
// like a `#[cfg]` being processed or some weird `macro_rules!`
// expansion.
//
// What we *don't* want to catch is the fact that a user-defined
// literal like `0xf` is stringified as `15`, causing the cached token
// stream to not be literal `==` token-wise (ignoring spans) to the
// token stream we got from stringification.
//
// Instead the "probably equal" check here is "does each token
// recursively have the same discriminant?" We basically don't look at
// the token values here and assume that such fine grained token stream
// modifications, including adding/removing typically non-semantic
// tokens such as extra braces and commas, don't happen.
if let Some(tokens) = tokens {
if GOOD_TOKEN_CACHE.with(|cache| cache.borrow().contains(&source)) {
return tokens;
}
// Compare with a non-relaxed delim match to start.
if tokenstream_probably_equal_for_proc_macro(&tokens, &reparsed_tokens, sess, false) {
GOOD_TOKEN_CACHE.with(|cache| cache.borrow_mut().insert(source.clone()));
return tokens;
}
// The check failed. This time, we pretty-print the AST struct with parenthesis
// inserted to preserve precedence. This may cause `None`-delimiters in the captured
// token stream to match up with inserted parenthesis in the reparsed stream.
let source_with_parens = pprust::nonterminal_to_string(nt);
let filename_with_parens = FileName::macro_expansion_source_code(&source_with_parens);
if GOOD_TOKEN_CACHE.with(|cache| cache.borrow().contains(&source_with_parens)) {
return tokens;
}
let reparsed_tokens_with_parens = parse_stream_from_source_str(
filename_with_parens,
source_with_parens,
sess,
Some(span),
);
// Compare with a relaxed delim match - we want inserted parenthesis in the
// reparsed stream to match `None`-delimiters in the original stream.
if tokenstream_probably_equal_for_proc_macro(
&tokens,
&reparsed_tokens_with_parens,
sess,
true,
) {
GOOD_TOKEN_CACHE.with(|cache| cache.borrow_mut().insert(source.clone()));
return tokens;
}
info!(
"cached tokens found, but they're not \"probably equal\", \
going with stringified version"
);
info!("cached tokens: {}", pprust::tts_to_string(&tokens));
info!("reparsed tokens: {}", pprust::tts_to_string(&reparsed_tokens_with_parens));
info!("cached tokens debug: {:?}", tokens);
info!("reparsed tokens debug: {:?}", reparsed_tokens_with_parens);
}
reparsed_tokens
}
// See comments in `Nonterminal::to_tokenstream` for why we care about
// *probably* equal here rather than actual equality
//
// This is otherwise the same as `eq_unspanned`, only recursing with a
// different method.
pub fn tokenstream_probably_equal_for_proc_macro(
tokens: &TokenStream,
reparsed_tokens: &TokenStream,
sess: &ParseSess,
relaxed_delim_match: bool,
) -> bool {
// When checking for `probably_eq`, we ignore certain tokens that aren't
// preserved in the AST. Because they are not preserved, the pretty
// printer arbitrarily adds or removes them when printing as token
// streams, making a comparison between a token stream generated from an
// AST and a token stream which was parsed into an AST more reliable.
fn semantic_tree(tree: &TokenTree) -> bool {
if let TokenTree::Token(token) = tree {
if let
// The pretty printer tends to add trailing commas to
// everything, and in particular, after struct fields.
| token::Comma
// The pretty printer collapses many semicolons into one.
| token::Semi
// We don't preserve leading `|` tokens in patterns, so
// we ignore them entirely
| token::BinOp(token::BinOpToken::Or)
// We don't preserve trailing '+' tokens in trait bounds,
// so we ignore them entirely
| token::BinOp(token::BinOpToken::Plus)
// The pretty printer can turn `$crate` into `::crate_name`
| token::ModSep = token.kind {
return false;
}
}
true
}
// When comparing two `TokenStream`s, we ignore the `IsJoint` information.
//
// However, `rustc_parse::lexer::tokentrees::TokenStreamBuilder` will
// use `Token.glue` on adjacent tokens with the proper `IsJoint`.
// Since we are ignoreing `IsJoint`, a 'glued' token (e.g. `BinOp(Shr)`)
// and its 'split'/'unglued' compoenents (e.g. `Gt, Gt`) are equivalent
// when determining if two `TokenStream`s are 'probably equal'.
//
// Therefore, we use `break_two_token_op` to convert all tokens
// to the 'unglued' form (if it exists). This ensures that two
// `TokenStream`s which differ only in how their tokens are glued
// will be considered 'probably equal', which allows us to keep spans.
//
// This is important when the original `TokenStream` contained
// extra spaces (e.g. `f :: < Vec < _ > > ( ) ;'). These extra spaces
// will be omitted when we pretty-print, which can cause the original
// and reparsed `TokenStream`s to differ in the assignment of `IsJoint`,
// leading to some tokens being 'glued' together in one stream but not
// the other. See #68489 for more details.
fn break_tokens(tree: TokenTree) -> impl Iterator<Item = TokenTree> {
// In almost all cases, we should have either zero or one levels
// of 'unglueing'. However, in some unusual cases, we may need
// to iterate breaking tokens mutliple times. For example:
// '[BinOpEq(Shr)] => [Gt, Ge] -> [Gt, Gt, Eq]'
let mut token_trees: SmallVec<[_; 2]>;
if let TokenTree::Token(token) = tree {
let mut out = SmallVec::<[_; 2]>::new();
out.push(token);
// Iterate to fixpoint:
// * We start off with 'out' containing our initial token, and `temp` empty
// * If we are able to break any tokens in `out`, then `out` will have
// at least one more element than 'temp', so we will try to break tokens
// again.
// * If we cannot break any tokens in 'out', we are done
loop {
let mut temp = SmallVec::<[_; 2]>::new();
let mut changed = false;
for token in out.into_iter() {
if let Some((first, second)) = token.kind.break_two_token_op() {
temp.push(Token::new(first, DUMMY_SP));
temp.push(Token::new(second, DUMMY_SP));
changed = true;
} else {
temp.push(token);
}
}
out = temp;
if !changed {
break;
}
}
token_trees = out.into_iter().map(TokenTree::Token).collect();
} else {
token_trees = SmallVec::new();
token_trees.push(tree);
}
token_trees.into_iter()
}
fn expand_token(tree: TokenTree, sess: &ParseSess) -> impl Iterator<Item = TokenTree> {
// When checking tokenstreams for 'probable equality', we are comparing
// a captured (from parsing) `TokenStream` to a reparsed tokenstream.
// The reparsed Tokenstream will never have `None`-delimited groups,
// since they are only ever inserted as a result of macro expansion.
// Therefore, inserting a `None`-delimtied group here (when we
// convert a nested `Nonterminal` to a tokenstream) would cause
// a mismatch with the reparsed tokenstream.
//
// Note that we currently do not handle the case where the
// reparsed stream has a `Parenthesis`-delimited group
// inserted. This will cause a spurious mismatch:
// issue #75734 tracks resolving this.
let expanded: SmallVec<[_; 1]> =
if let TokenTree::Token(Token { kind: TokenKind::Interpolated(nt), span }) = &tree {
nt_to_tokenstream(nt, sess, *span)
.into_trees()
.flat_map(|t| expand_token(t, sess))
.collect()
} else {
// Filter before and after breaking tokens,
// since we may want to ignore both glued and unglued tokens.
std::iter::once(tree)
.filter(semantic_tree)
.flat_map(break_tokens)
.filter(semantic_tree)
.collect()
};
expanded.into_iter()
}
// Break tokens after we expand any nonterminals, so that we break tokens
// that are produced as a result of nonterminal expansion.
let tokens = tokens.trees().flat_map(|t| expand_token(t, sess));
let reparsed_tokens = reparsed_tokens.trees().flat_map(|t| expand_token(t, sess));
tokens.eq_by(reparsed_tokens, |t, rt| {
tokentree_probably_equal_for_proc_macro(&t, &rt, sess, relaxed_delim_match)
})
}
// See comments in `Nonterminal::to_tokenstream` for why we care about
// *probably* equal here rather than actual equality
//
// This is otherwise the same as `eq_unspanned`, only recursing with a
// different method.
pub fn tokentree_probably_equal_for_proc_macro(
token: &TokenTree,
reparsed_token: &TokenTree,
sess: &ParseSess,
relaxed_delim_match: bool,
) -> bool {
match (token, reparsed_token) {
(TokenTree::Token(token), TokenTree::Token(reparsed_token)) => {
token_probably_equal_for_proc_macro(token, reparsed_token)
}
(
TokenTree::Delimited(_, delim, tokens),
TokenTree::Delimited(_, reparsed_delim, reparsed_tokens),
) if delim == reparsed_delim => tokenstream_probably_equal_for_proc_macro(
tokens,
reparsed_tokens,
sess,
relaxed_delim_match,
),
(TokenTree::Delimited(_, DelimToken::NoDelim, tokens), reparsed_token) => {
if relaxed_delim_match {
if let TokenTree::Delimited(_, DelimToken::Paren, reparsed_tokens) = reparsed_token
{
if tokenstream_probably_equal_for_proc_macro(
tokens,
reparsed_tokens,
sess,
relaxed_delim_match,
) {
return true;
}
}
}
tokens.len() == 1
&& tokentree_probably_equal_for_proc_macro(
&tokens.trees().next().unwrap(),
reparsed_token,
sess,
relaxed_delim_match,
)
}
_ => false,
return tokens;
} else if matches!(synthesize_tokens, CanSynthesizeMissingTokens::Yes) {
return fake_token_stream(sess, nt, span);
} else {
let pretty = rustc_ast_pretty::pprust::nonterminal_to_string_no_extra_parens(&nt);
panic!("Missing tokens at {:?} for nt {:?}", span, pretty);
}
}
// See comments in `Nonterminal::to_tokenstream` for why we care about
// *probably* equal here rather than actual equality
fn token_probably_equal_for_proc_macro(first: &Token, other: &Token) -> bool {
if mem::discriminant(&first.kind) != mem::discriminant(&other.kind) {
return false;
}
use rustc_ast::token::TokenKind::*;
match (&first.kind, &other.kind) {
(&Eq, &Eq)
| (&Lt, &Lt)
| (&Le, &Le)
| (&EqEq, &EqEq)
| (&Ne, &Ne)
| (&Ge, &Ge)
| (&Gt, &Gt)
| (&AndAnd, &AndAnd)
| (&OrOr, &OrOr)
| (&Not, &Not)
| (&Tilde, &Tilde)
| (&At, &At)
| (&Dot, &Dot)
| (&DotDot, &DotDot)
| (&DotDotDot, &DotDotDot)
| (&DotDotEq, &DotDotEq)
| (&Comma, &Comma)
| (&Semi, &Semi)
| (&Colon, &Colon)
| (&ModSep, &ModSep)
| (&RArrow, &RArrow)
| (&LArrow, &LArrow)
| (&FatArrow, &FatArrow)
| (&Pound, &Pound)
| (&Dollar, &Dollar)
| (&Question, &Question)
| (&Eof, &Eof) => true,
(&BinOp(a), &BinOp(b)) | (&BinOpEq(a), &BinOpEq(b)) => a == b,
(&OpenDelim(a), &OpenDelim(b)) | (&CloseDelim(a), &CloseDelim(b)) => a == b,
(&DocComment(a1, a2, a3), &DocComment(b1, b2, b3)) => a1 == b1 && a2 == b2 && a3 == b3,
(&Literal(a), &Literal(b)) => a == b,
(&Lifetime(a), &Lifetime(b)) => a == b,
(&Ident(a, b), &Ident(c, d)) => {
b == d && (a == c || a == kw::DollarCrate || c == kw::DollarCrate)
}
(&Interpolated(..), &Interpolated(..)) => panic!("Unexpanded Interpolated!"),
_ => panic!("forgot to add a token?"),
}
pub fn fake_token_stream(sess: &ParseSess, nt: &Nonterminal, span: Span) -> TokenStream {
let source = pprust::nonterminal_to_string(nt);
let filename = FileName::macro_expansion_source_code(&source);
parse_stream_from_source_str(filename, source, sess, Some(span))
}
fn prepend_attrs(
sess: &ParseSess,
attrs: &[ast::Attribute],
nt: &Nonterminal,
span: Span,
tokens: Option<&tokenstream::LazyTokenStream>,
) -> Option<tokenstream::TokenStream> {
let tokens = tokens?.create_token_stream();
if attrs.is_empty() {
return Some(tokens);
return Some(tokens?.create_token_stream());
}
let mut builder = tokenstream::TokenStreamBuilder::new();
for attr in attrs {
// FIXME: Correctly handle tokens for inner attributes.
// For now, we fall back to reparsing the original AST node
if attr.style == ast::AttrStyle::Inner {
return None;
return Some(fake_token_stream(sess, nt, span));
}
builder.push(attr.tokens());
}
builder.push(tokens);
builder.push(tokens?.create_token_stream());
Some(builder.build())
}