rustc: Forbid interpolated tokens in the HIR #44601
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Right now the HIR contains raw `syntax::ast::Attribute` structure but nowadays
these can contain arbitrary tokens. One variant of the `Token` enum is an
"interpolated" token which basically means to shove all the tokens for a
nonterminal in this position. A "nonterminal" in this case is roughly analagous
to a macro argument:
macro_rules! foo {
($a:expr) => {
// $a is a nonterminal as an expression
}
}
Currently nonterminals contain namely items and expressions, and this poses a
problem for incremental compilation! With incremental we want a stable hash of
all HIR items, but this means we may transitively need a stable hash *of the
entire AST*, which is certainly not stable w/ node ids and whatnot. Hence today
there's a "bug" where the "stable hash" of an AST is just the raw hash value of
the AST, and this only arises with interpolated nonterminals. The downside of
this approach, however, is that a bunch of errors get spewed out during
compilation about how this isn't a great idea.
This PR is focused at fixing these warnings, basically deleting them from the
compiler. The implementation here is to alter attributes as they're lowered from
the AST to HIR, expanding all nonterminals in-place as we see them. This code
for expanding a nonterminal to a token stream already exists for the
`proc_macro` crate, so we basically just reuse the same implementation there.
After this PR it's considered a bug to have an `Interpolated` token and hence
the stable hash implementation simply uses `bug!` in this location.
Closes rust-lang#40946
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Sep 19, 2017
rustc: Forbid interpolated tokens in the HIR
Right now the HIR contains raw `syntax::ast::Attribute` structure but nowadays
these can contain arbitrary tokens. One variant of the `Token` enum is an
"interpolated" token which basically means to shove all the tokens for a
nonterminal in this position. A "nonterminal" in this case is roughly analagous
to a macro argument:
macro_rules! foo {
($a:expr) => {
// $a is a nonterminal as an expression
}
}
Currently nonterminals contain namely items and expressions, and this poses a
problem for incremental compilation! With incremental we want a stable hash of
all HIR items, but this means we may transitively need a stable hash *of the
entire AST*, which is certainly not stable w/ node ids and whatnot. Hence today
there's a "bug" where the "stable hash" of an AST is just the raw hash value of
the AST, and this only arises with interpolated nonterminals. The downside of
this approach, however, is that a bunch of errors get spewed out during
compilation about how this isn't a great idea.
This PR is focused at fixing these warnings, basically deleting them from the
compiler. The implementation here is to alter attributes as they're lowered from
the AST to HIR, expanding all nonterminals in-place as we see them. This code
for expanding a nonterminal to a token stream already exists for the
`proc_macro` crate, so we basically just reuse the same implementation there.
After this PR it's considered a bug to have an `Interpolated` token and hence
the stable hash implementation simply uses `bug!` in this location.
Closes #40946
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☀️ Test successful - status-appveyor, status-travis |
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This may have caused a regression wrt doc attributes |
alexcrichton
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Sep 21, 2017
This commit fixes a regression from rust-lang#44601 where lowering attribute to HIR now involves expanding interpolated tokens to their actual tokens. In that commit all interpolated tokens were surrounded with a `DelimToken::None` group of tokens, but this ended up causing regressions like rust-lang#44730 where the various attribute parsers in `syntax/attr.rs` weren't ready to cope with `DelimToken::None`. Instead of fixing the parser in `attr.rs` this commit instead opts to just avoid the `DelimToken::None` in the first place, ensuring that the token stream should look the same as it did before where possible. Closes rust-lang#44730
frewsxcv
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Sep 23, 2017
rustc: Don't use DelimToken::None if possible This commit fixes a regression from rust-lang#44601 where lowering attribute to HIR now involves expanding interpolated tokens to their actual tokens. In that commit all interpolated tokens were surrounded with a `DelimToken::None` group of tokens, but this ended up causing regressions like rust-lang#44730 where the various attribute parsers in `syntax/attr.rs` weren't ready to cope with `DelimToken::None`. Instead of fixing the parser in `attr.rs` this commit instead opts to just avoid the `DelimToken::None` in the first place, ensuring that the token stream should look the same as it did before where possible. Closes rust-lang#44730
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Right now the HIR contains raw
syntax::ast::Attributestructure but nowadaysthese can contain arbitrary tokens. One variant of the
Tokenenum is an"interpolated" token which basically means to shove all the tokens for a
nonterminal in this position. A "nonterminal" in this case is roughly analagous
to a macro argument:
Currently nonterminals contain namely items and expressions, and this poses a
problem for incremental compilation! With incremental we want a stable hash of
all HIR items, but this means we may transitively need a stable hash of the
entire AST, which is certainly not stable w/ node ids and whatnot. Hence today
there's a "bug" where the "stable hash" of an AST is just the raw hash value of
the AST, and this only arises with interpolated nonterminals. The downside of
this approach, however, is that a bunch of errors get spewed out during
compilation about how this isn't a great idea.
This PR is focused at fixing these warnings, basically deleting them from the
compiler. The implementation here is to alter attributes as they're lowered from
the AST to HIR, expanding all nonterminals in-place as we see them. This code
for expanding a nonterminal to a token stream already exists for the
proc_macrocrate, so we basically just reuse the same implementation there.After this PR it's considered a bug to have an
Interpolatedtoken and hencethe stable hash implementation simply uses
bug!in this location.Closes #40946