Instead of updating global state to mark attributes as used,
we now explicitly emit a warning when an attribute is used in
an unsupported position. As a side effect, we are to emit more
detailed warning messages (instead of just a generic "unused" message).
`Session.check_name` is removed, since its only purpose was to mark
the attribute as used. All of the callers are modified to use
`Attribute.has_name`
Additionally, `AttributeType::AssumedUsed` is removed - an 'assumed
used' attribute is implemented by simply not performing any checks
in `CheckAttrVisitor` for a particular attribute.
We no longer emit unused attribute warnings for the `#[rustc_dummy]`
attribute - it's an internal attribute used for tests, so it doesn't
mark sense to treat it as 'unused'.
With this commit, a large source of global untracked state is removed.
Lint against named asm labels
This adds a deny-by-default lint to prevent the use of named labels in inline `asm!`. Without a solution to #81088 about whether the compiler should rewrite named labels or a special syntax for labels, a lint against them should prevent users from writing assembly that could break for internal compiler reasons, such as inlining or anything else that could change the number of actual inline assembly blocks emitted.
This does **not** resolve the issue with rewriting labels, that still needs a decision if the compiler should do any more work to try to make them work.
Move naked function ABI check to its own lint
This check was previously categorized under the lint named
`UNSUPPORTED_NAKED_FUNCTIONS`. That lint is future incompatible and will
be turned into an error in a future release. However, as defined in the
Constrained Naked Functions RFC, this check should only be a warning.
This is because it is possible for a naked function to be implemented in
such a way that it does not break even the undefined ABI. For example, a
`jmp` to a `const`.
Therefore, this patch defines a new lint named
`UNDEFINED_NAKED_FUNCTION_ABI` which contains just this single check.
Unlike `UNSUPPORTED_NAKED_FUNCTIONS`, `UNDEFINED_NAKED_FUNCTION_ABI`
will not be converted to an error in the future.
rust-lang/rfcs#2774rust-lang/rfcs#2972
This check was previously categorized under the lint named
`UNSUPPORTED_NAKED_FUNCTIONS`. That lint is future incompatible and will
be turned into an error in a future release. However, as defined in the
Constrained Naked Functions RFC, this check should only be a warning.
This is because it is possible for a naked function to be implemented in
such a way that it does not break even the undefined ABI. For example, a
`jmp` to a `const`.
Therefore, this patch defines a new lint named
`UNDEFINED_NAKED_FUNCTION_ABI` which contains just this single check.
Unlike `UNSUPPORTED_NAKED_FUNCTIONS`, `UNDEFINED_NAKED_FUNCTION_ABI`
will not be converted to an error in the future.
rust-lang/rfcs#2774rust-lang/rfcs#2972
Allow labeled loops as value expressions for `break`
Fixes#86948. This is currently allowed:
```rust
return 'label: loop { break 'label 42; };
break ('label: loop { break 'label 42; });
break 1 + 'label: loop { break 'label 42; };
break 'outer 'inner: loop { break 'inner 42; };
```
But not this:
```rust
break 'label: loop { break 'label 42; };
```
I have fixed this, so that the above now parses as an unlabeled break with a labeled loop as its value expression.
Currently, we parse macros at the end of a block
(e.g. `fn foo() { my_macro!() }`) as expressions, rather than
statements. This means that a macro invoked in this position
cannot expand to items or semicolon-terminated expressions.
In the future, we might want to start parsing these kinds of macros
as statements. This would make expansion more 'token-based'
(i.e. macro expansion behaves (almost) as if you just textually
replaced the macro invocation with its output). However,
this is a breaking change (see PR #78991), so it will require
further discussion.
Since the current behavior will not be changing any time soon,
we need to address the interaction with the
`SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` lint. Since we are parsing
the result of macro expansion as an expression, we will emit a lint
if there's a trailing semicolon in the macro output. However, this
results in a somewhat confusing message for users, since it visually
looks like there should be no problem with having a semicolon
at the end of a block
(e.g. `fn foo() { my_macro!() }` => `fn foo() { produced_expr; }`)
To help reduce confusion, this commit adds a note explaining
that the macro is being interpreted as an expression. Additionally,
we suggest adding a semicolon after the macro *invocation* - this
will cause us to parse the macro call as a statement. We do *not*
use a structured suggestion for this, since the user may actually
want to remove the semicolon from the macro definition (allowing
the block to evaluate to the expression produced by the macro).
Warn on inert attributes used on bang macro invocation
These attributes are currently discarded.
This may change in the future (see #63221), but for now,
placing inert attributes on a macro invocation does nothing,
so we should warn users about it.
Technically, it's possible for there to be attribute macro
on the same macro invocation (or at a higher scope), which
inspects the inert attribute. For example:
```rust
#[look_for_inline_attr]
#[inline]
my_macro!()
#[look_for_nested_inline]
mod foo { #[inline] my_macro!() }
```
However, this would be a very strange thing to do.
Anyone running into this can manually suppress the warning.
These attributes are currently discarded.
This may change in the future (see #63221), but for now,
placing inert attributes on a macro invocation does nothing,
so we should warn users about it.
Technically, it's possible for there to be attribute macro
on the same macro invocation (or at a higher scope), which
inspects the inert attribute. For example:
```rust
#[look_for_inline_attr]
#[inline]
my_macro!()
#[look_for_nested_inline]
mod foo { #[inline] my_macro!() }
```
However, this would be a very strange thing to do.
Anyone running into this can manually suppress the warning.
When we need to emit a lint at a macro invocation, we currently use the
`NodeId` of its parent definition (e.g. the enclosing function). This
means that any `#[allow]` / `#[deny]` attributes placed 'closer' to the
macro (e.g. on an enclosing block or statement) will have no effect.
This commit computes a better `lint_node_id` in `InvocationCollector`.
When we visit/flat_map an AST node, we assign it a `NodeId` (earlier
than we normally would), and store than `NodeId` in current
`ExpansionData`. When we collect a macro invocation, the current
`lint_node_id` gets cloned along with our `ExpansionData`, allowing it
to be used if we need to emit a lint later on.
This improves the handling of `#[allow]` / `#[deny]` for
`SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` and some `asm!`-related lints.
The 'legacy derive helpers' lint retains its current behavior
(I've inlined the now-removed `lint_node_id` function), since
there isn't an `ExpansionData` readily available.
It makes very little sense to maintain denylists of ABIs when, as far as
non-generic ABIs are concerned, targets usually only support a small
subset of the available ABIs.
This has historically been a cause of bugs such as us allowing use of
the platform-specific ABIs on x86 targets – these in turn would cause
LLVM errors or assertions to fire.
Fixes#57182
Sponsored by: standard.ai
Turn non_fmt_panic into a future_incompatible edition lint.
This turns the `non_fmt_panic` lint into a future_incompatible edition lint, so it becomes part of the `rust_2021_compatibility` group. See https://github.com/rust-lang/rust/issues/85894.
This lint produces both warnings about semantical changes (e.g. `panic!("{{")`) and things that will become hard errors (e.g. `panic!("{")`). So I added a `explain_reason: false` that supresses the default "this will become a hard error" or "the semantics will change" message, and instead added a note depending on the situation. (cc `@rylev)`
r? `@nikomatsakis`
Add `future_prelude_collision` lint
Implements #84594. (RFC rust-lang/rfcs#3114 ([rendered](https://github.com/rust-lang/rfcs/blob/master/text/3114-prelude-2021.md))) Not entirely complete but wanted to have my progress decently available while I finish off the last little bits.
Things left to implement:
* [x] UI tests for lints
* [x] Only emit lint for 2015 and 2018 editions
* [ ] Lint name/message bikeshedding
* [x] Implement for `FromIterator` (from best I can tell, the current approach as mentioned from [this comment](https://github.com/rust-lang/rust/issues/84594#issuecomment-847288288) won't work due to `FromIterator` instances not using dot-call syntax, but if I'm correct about this then that would also need to be fixed for `TryFrom`/`TryInto`)*
* [x] Add to `rust-2021-migration` group? (See #85512) (added to `rust-2021-compatibility` group)
* [ ] Link to edition guide in lint docs
*edit: looked into it, `lookup_method` will also not be hit for `TryFrom`/`TryInto` for non-dotcall syntax. If anyone who is more familiar with typecheck knows the equivalent for looking up associated functions, feel free to chime in.
