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Rearrange TokenTreesReader::parse_token_tree.

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`parse_token_tree` is basically a match with four arms: `Eof`,
`OpenDelim`, `CloseDelim`, and "other". It has two call sites, and at
each call site one of the arms is unreachable. It's also not inlined.

This commit removes `parse_token_tree` by splitting it into four
functions and inlining them. This avoids some repeated conditional
tests and also some non-inlined function calls on the hot path.
This commit is contained in:
Nicholas Nethercote 2022-09-21 14:01:39 +10:00
parent f3fafbb006
commit 66e9b1149c
2 changed files with 189 additions and 198 deletions
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3
compiler/rustc_errors/src/lib.rs
View File

@ -63,7 +63,8 @@ pub mod translation;
pub use diagnostic_builder::IntoDiagnostic;
pub use snippet::Style;
pub type PResult<'a, T> = Result<T, DiagnosticBuilder<'a, ErrorGuaranteed>>;
pub type PErr<'a> = DiagnosticBuilder<'a, ErrorGuaranteed>;
pub type PResult<'a, T> = Result<T, PErr<'a>>;
// `PResult` is used a lot. Make sure it doesn't unintentionally get bigger.
// (See also the comment on `DiagnosticBuilder`'s `diagnostic` field.)

384
compiler/rustc_parse/src/lexer/tokentrees.rs
View File

@ -4,7 +4,7 @@ use rustc_ast::token::{self, Delimiter, Token};
use rustc_ast::tokenstream::{DelimSpan, Spacing, TokenStream, TokenTree};
use rustc_ast_pretty::pprust::token_to_string;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::PResult;
use rustc_errors::{PErr, PResult};
use rustc_span::Span;
impl<'a> StringReader<'a> {
@ -48,220 +48,210 @@ impl<'a> TokenTreesReader<'a> {
let mut buf = TokenStreamBuilder::default();
self.bump();
while self.token != token::Eof {
buf.push(self.parse_token_tree()?);
loop {
match self.token.kind {
token::OpenDelim(delim) => buf.push(self.parse_token_tree_open_delim(delim)),
token::CloseDelim(delim) => return Err(self.close_delim_err(delim)),
token::Eof => return Ok(buf.into_token_stream()),
_ => buf.push(self.parse_token_tree_other()),
}
}
Ok(buf.into_token_stream())
}
// Parse a stream of tokens into a list of `TokenTree`s, up to a `CloseDelim`.
fn parse_token_trees_until_close_delim(&mut self) -> TokenStream {
let mut buf = TokenStreamBuilder::default();
loop {
if let token::CloseDelim(..) = self.token.kind {
return buf.into_token_stream();
}
match self.parse_token_tree() {
Ok(tree) => buf.push(tree),
Err(mut e) => {
e.emit();
match self.token.kind {
token::OpenDelim(delim) => buf.push(self.parse_token_tree_open_delim(delim)),
token::CloseDelim(..) => return buf.into_token_stream(),
token::Eof => {
let mut err = self.eof_err();
err.emit();
return buf.into_token_stream();
}
_ => buf.push(self.parse_token_tree_other()),
}
}
}
fn parse_token_tree(&mut self) -> PResult<'a, TokenTree> {
let sm = self.string_reader.sess.source_map();
fn eof_err(&mut self) -> PErr<'a> {
let msg = "this file contains an unclosed delimiter";
let mut err = self.string_reader.sess.span_diagnostic.struct_span_err(self.token.span, msg);
for &(_, sp) in &self.open_braces {
err.span_label(sp, "unclosed delimiter");
self.unmatched_braces.push(UnmatchedBrace {
expected_delim: Delimiter::Brace,
found_delim: None,
found_span: self.token.span,
unclosed_span: Some(sp),
candidate_span: None,
});
}
match self.token.kind {
token::Eof => {
let msg = "this file contains an unclosed delimiter";
let mut err =
self.string_reader.sess.span_diagnostic.struct_span_err(self.token.span, msg);
for &(_, sp) in &self.open_braces {
err.span_label(sp, "unclosed delimiter");
self.unmatched_braces.push(UnmatchedBrace {
expected_delim: Delimiter::Brace,
found_delim: None,
found_span: self.token.span,
unclosed_span: Some(sp),
candidate_span: None,
});
}
if let Some((delim, _)) = self.open_braces.last() {
if let Some((_, open_sp, close_sp)) =
self.matching_delim_spans.iter().find(|(d, open_sp, close_sp)| {
if let Some(close_padding) = sm.span_to_margin(*close_sp) {
if let Some(open_padding) = sm.span_to_margin(*open_sp) {
return delim == d && close_padding != open_padding;
}
}
false
})
// these are in reverse order as they get inserted on close, but
{
// we want the last open/first close
err.span_label(*open_sp, "this delimiter might not be properly closed...");
err.span_label(
*close_sp,
"...as it matches this but it has different indentation",
);
}
}
Err(err)
}
token::OpenDelim(delim) => {
// The span for beginning of the delimited section
let pre_span = self.token.span;
// Parse the open delimiter.
self.open_braces.push((delim, self.token.span));
self.bump();
// Parse the token trees within the delimiters.
// We stop at any delimiter so we can try to recover if the user
// uses an incorrect delimiter.
let tts = self.parse_token_trees_until_close_delim();
// Expand to cover the entire delimited token tree
let delim_span = DelimSpan::from_pair(pre_span, self.token.span);
match self.token.kind {
// Correct delimiter.
token::CloseDelim(d) if d == delim => {
let (open_brace, open_brace_span) = self.open_braces.pop().unwrap();
let close_brace_span = self.token.span;
if tts.is_empty() {
let empty_block_span = open_brace_span.to(close_brace_span);
if !sm.is_multiline(empty_block_span) {
// Only track if the block is in the form of `{}`, otherwise it is
// likely that it was written on purpose.
self.last_delim_empty_block_spans.insert(delim, empty_block_span);
}
}
//only add braces
if let (Delimiter::Brace, Delimiter::Brace) = (open_brace, delim) {
self.matching_block_spans.push((open_brace_span, close_brace_span));
}
if self.open_braces.is_empty() {
// Clear up these spans to avoid suggesting them as we've found
// properly matched delimiters so far for an entire block.
self.matching_delim_spans.clear();
} else {
self.matching_delim_spans.push((
open_brace,
open_brace_span,
close_brace_span,
));
}
// Parse the closing delimiter.
self.bump();
}
// Incorrect delimiter.
token::CloseDelim(other) => {
let mut unclosed_delimiter = None;
let mut candidate = None;
if self.last_unclosed_found_span != Some(self.token.span) {
// do not complain about the same unclosed delimiter multiple times
self.last_unclosed_found_span = Some(self.token.span);
// This is a conservative error: only report the last unclosed
// delimiter. The previous unclosed delimiters could actually be
// closed! The parser just hasn't gotten to them yet.
if let Some(&(_, sp)) = self.open_braces.last() {
unclosed_delimiter = Some(sp);
};
if let Some(current_padding) = sm.span_to_margin(self.token.span) {
for (brace, brace_span) in &self.open_braces {
if let Some(padding) = sm.span_to_margin(*brace_span) {
// high likelihood of these two corresponding
if current_padding == padding && brace == &other {
candidate = Some(*brace_span);
}
}
}
}
let (tok, _) = self.open_braces.pop().unwrap();
self.unmatched_braces.push(UnmatchedBrace {
expected_delim: tok,
found_delim: Some(other),
found_span: self.token.span,
unclosed_span: unclosed_delimiter,
candidate_span: candidate,
});
} else {
self.open_braces.pop();
}
// If the incorrect delimiter matches an earlier opening
// delimiter, then don't consume it (it can be used to
// close the earlier one). Otherwise, consume it.
// E.g., we try to recover from:
// fn foo() {
// bar(baz(
// } // Incorrect delimiter but matches the earlier `{`
if !self.open_braces.iter().any(|&(b, _)| b == other) {
self.bump();
if let Some((delim, _)) = self.open_braces.last() {
if let Some((_, open_sp, close_sp)) =
self.matching_delim_spans.iter().find(|(d, open_sp, close_sp)| {
let sm = self.string_reader.sess.source_map();
if let Some(close_padding) = sm.span_to_margin(*close_sp) {
if let Some(open_padding) = sm.span_to_margin(*open_sp) {
return delim == d && close_padding != open_padding;
}
}
token::Eof => {
// Silently recover, the EOF token will be seen again
// and an error emitted then. Thus we don't pop from
// self.open_braces here.
}
_ => {}
}
Ok(TokenTree::Delimited(delim_span, delim, tts))
}
token::CloseDelim(delim) => {
// An unexpected closing delimiter (i.e., there is no
// matching opening delimiter).
let token_str = token_to_string(&self.token);
let msg = format!("unexpected closing delimiter: `{}`", token_str);
let mut err =
self.string_reader.sess.span_diagnostic.struct_span_err(self.token.span, &msg);
// Braces are added at the end, so the last element is the biggest block
if let Some(parent) = self.matching_block_spans.last() {
if let Some(span) = self.last_delim_empty_block_spans.remove(&delim) {
// Check if the (empty block) is in the last properly closed block
if (parent.0.to(parent.1)).contains(span) {
err.span_label(
span,
"block is empty, you might have not meant to close it",
);
} else {
err.span_label(parent.0, "this opening brace...");
err.span_label(parent.1, "...matches this closing brace");
}
} else {
err.span_label(parent.0, "this opening brace...");
err.span_label(parent.1, "...matches this closing brace");
}
}
err.span_label(self.token.span, "unexpected closing delimiter");
Err(err)
}
_ => {
let tok = self.token.take();
let mut spacing = self.bump();
if !self.token.is_op() {
spacing = Spacing::Alone;
}
Ok(TokenTree::Token(tok, spacing))
false
})
// these are in reverse order as they get inserted on close, but
{
// we want the last open/first close
err.span_label(*open_sp, "this delimiter might not be properly closed...");
err.span_label(*close_sp, "...as it matches this but it has different indentation");
}
}
err
}
fn parse_token_tree_open_delim(&mut self, delim: Delimiter) -> TokenTree {
// The span for beginning of the delimited section
let pre_span = self.token.span;
// Parse the open delimiter.
self.open_braces.push((delim, self.token.span));
self.bump();
// Parse the token trees within the delimiters.
// We stop at any delimiter so we can try to recover if the user
// uses an incorrect delimiter.
let tts = self.parse_token_trees_until_close_delim();
// Expand to cover the entire delimited token tree
let delim_span = DelimSpan::from_pair(pre_span, self.token.span);
match self.token.kind {
// Correct delimiter.
token::CloseDelim(d) if d == delim => {
let (open_brace, open_brace_span) = self.open_braces.pop().unwrap();
let close_brace_span = self.token.span;
if tts.is_empty() {
let empty_block_span = open_brace_span.to(close_brace_span);
let sm = self.string_reader.sess.source_map();
if !sm.is_multiline(empty_block_span) {
// Only track if the block is in the form of `{}`, otherwise it is
// likely that it was written on purpose.
self.last_delim_empty_block_spans.insert(delim, empty_block_span);
}
}
//only add braces
if let (Delimiter::Brace, Delimiter::Brace) = (open_brace, delim) {
self.matching_block_spans.push((open_brace_span, close_brace_span));
}
if self.open_braces.is_empty() {
// Clear up these spans to avoid suggesting them as we've found
// properly matched delimiters so far for an entire block.
self.matching_delim_spans.clear();
} else {
self.matching_delim_spans.push((open_brace, open_brace_span, close_brace_span));
}
// Parse the closing delimiter.
self.bump();
}
// Incorrect delimiter.
token::CloseDelim(other) => {
let mut unclosed_delimiter = None;
let mut candidate = None;
if self.last_unclosed_found_span != Some(self.token.span) {
// do not complain about the same unclosed delimiter multiple times
self.last_unclosed_found_span = Some(self.token.span);
// This is a conservative error: only report the last unclosed
// delimiter. The previous unclosed delimiters could actually be
// closed! The parser just hasn't gotten to them yet.
if let Some(&(_, sp)) = self.open_braces.last() {
unclosed_delimiter = Some(sp);
};
let sm = self.string_reader.sess.source_map();
if let Some(current_padding) = sm.span_to_margin(self.token.span) {
for (brace, brace_span) in &self.open_braces {
if let Some(padding) = sm.span_to_margin(*brace_span) {
// high likelihood of these two corresponding
if current_padding == padding && brace == &other {
candidate = Some(*brace_span);
}
}
}
}
let (tok, _) = self.open_braces.pop().unwrap();
self.unmatched_braces.push(UnmatchedBrace {
expected_delim: tok,
found_delim: Some(other),
found_span: self.token.span,
unclosed_span: unclosed_delimiter,
candidate_span: candidate,
});
} else {
self.open_braces.pop();
}
// If the incorrect delimiter matches an earlier opening
// delimiter, then don't consume it (it can be used to
// close the earlier one). Otherwise, consume it.
// E.g., we try to recover from:
// fn foo() {
// bar(baz(
// } // Incorrect delimiter but matches the earlier `{`
if !self.open_braces.iter().any(|&(b, _)| b == other) {
self.bump();
}
}
token::Eof => {
// Silently recover, the EOF token will be seen again
// and an error emitted then. Thus we don't pop from
// self.open_braces here.
}
_ => {}
}
TokenTree::Delimited(delim_span, delim, tts)
}
fn close_delim_err(&mut self, delim: Delimiter) -> PErr<'a> {
// An unexpected closing delimiter (i.e., there is no
// matching opening delimiter).
let token_str = token_to_string(&self.token);
let msg = format!("unexpected closing delimiter: `{}`", token_str);
let mut err =
self.string_reader.sess.span_diagnostic.struct_span_err(self.token.span, &msg);
// Braces are added at the end, so the last element is the biggest block
if let Some(parent) = self.matching_block_spans.last() {
if let Some(span) = self.last_delim_empty_block_spans.remove(&delim) {
// Check if the (empty block) is in the last properly closed block
if (parent.0.to(parent.1)).contains(span) {
err.span_label(span, "block is empty, you might have not meant to close it");
} else {
err.span_label(parent.0, "this opening brace...");
err.span_label(parent.1, "...matches this closing brace");
}
} else {
err.span_label(parent.0, "this opening brace...");
err.span_label(parent.1, "...matches this closing brace");
}
}
err.span_label(self.token.span, "unexpected closing delimiter");
err
}
#[inline]
fn parse_token_tree_other(&mut self) -> TokenTree {
let tok = self.token.take();
let mut spacing = self.bump();
if !self.token.is_op() {
spacing = Spacing::Alone;
}
TokenTree::Token(tok, spacing)
}
fn bump(&mut self) -> Spacing {