`Cursor` is currently hidden, and the main tokenization path uses
`rustc_lexer::first_token` which involves constructing a new `Cursor`
for every single token, which is weird. Also, `first_token` also can't
handle empty input, so callers have to check for that first.
This commit makes `Cursor` public, so `StringReader` can contain a
`Cursor`, which results in a simpler structure. The commit also changes
`StringReader::advance_token` so it returns an `Option<Token>`,
simplifying the the empty input case.
`TokenTreesReader` wraps a `StringReader`, but the `into_token_trees`
function obscures this. This commit moves to a more straightforward
control flow.
The spacing computation is done in two parts. In the first part
`next_token` and `bump` use `Spacing::Alone` to mean "preceded by
whitespace" and `Spacing::Joint` to mean the opposite. In the second
part `parse_token_tree_other` then adjusts the `spacing` value to mean
the usual thing (i.e. "is the following token joinable punctuation?").
This shift in meaning is very confusing and it took me some time to
understand what was going on.
This commit changes the first part to use a bool, and adds some
comments, which makes things much clearer.
From 72 bytes to 12 bytes (on x86-64).
There are two parts to this:
- Changing various source code offsets from 64-bit to 32-bit. This is
not a problem because the rest of rustc also uses 32-bit source code
offsets. This means `Token` is no longer `Copy` but this causes no
problems.
- Removing the `RawStrError` from `LiteralKind`. Raw string literal
invalidity is now indicated by a `None` value within
`RawStr`/`RawByteStr`, and the new `validate_raw_str` function can be
used to re-lex an invalid raw string literal to get the `RawStrError`.
There is one very small change in behaviour. Previously, if a raw string
literal matched both the `InvalidStarter` and `TooManyHashes` cases,
the latter would override the former. This has now changed, because
`raw_double_quoted_string` now uses `?` and so returns immediately upon
detecting the `InvalidStarter` case. I think this is a slight
improvement to report the earlier-detected error, and it explains the
change in the `test_too_many_hashes` test.
The commit also removes a couple of comments that refer to #77629 and
say that the size of these types don't affect performance. These
comments are wrong, though the performance effect is small.
Change `span_suggestion` (and variants) to take `impl ToString` rather
than `String` for the suggested code, as this simplifies the
requirements on the diagnostic derive.
Signed-off-by: David Wood <david.wood@huawei.com>
Improve diagnostics for unterminated nested block comment
close#95283
(This is my first time try to messing around with rust compiler and might get a lot of things wrong... 🙇 )
