rust/src/librustc/lint/builtin.rs
Niko Matsakis f69eb8efbe issue a future-compat lint for constants of invalid type
This is a [breaking-change]: according to RFC #1445, constants used as
patterns must be of a type that *derives* `Eq`. If you encounter a
problem, you are most likely using a constant in an expression where the
type of the constant is some struct that does not currently implement
`Eq`. Something like the following:

```rust
struct SomeType { ... }
const SOME_CONST: SomeType = ...;

match foo {
    SOME_CONST => ...
}
```

The easiest and most future compatible fix is to annotate the type in
question with `#[derive(Eq)]` (note that merely *implementing* `Eq` is
not enough, it must be *derived*):

```rust
struct SomeType { ... }
const SOME_CONST: SomeType = ...;

match foo {
    SOME_CONST => ...
}
```

Another good option is to rewrite the match arm to use an `if`
condition (this is also particularly good for floating point types,
which implement `PartialEq` but not `Eq`):

```rust
match foo {
    c if c == SOME_CONST => ...
}
```

Finally, a third alternative is to tag the type with
`#[structural_match]`; but this is not recommended, as the attribute is
never expected to be stabilized. Please see RFC #1445 for more details.
2016-03-25 06:45:42 -04:00

222 lines
5.1 KiB
Rust

// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Some lints that are built in to the compiler.
//!
//! These are the built-in lints that are emitted direct in the main
//! compiler code, rather than using their own custom pass. Those
//! lints are all available in `rustc_lint::builtin`.
use lint::{LintPass, LateLintPass, LintArray};
declare_lint! {
pub CONST_ERR,
Warn,
"constant evaluation detected erroneous expression"
}
declare_lint! {
pub UNUSED_IMPORTS,
Warn,
"imports that are never used"
}
declare_lint! {
pub UNUSED_EXTERN_CRATES,
Allow,
"extern crates that are never used"
}
declare_lint! {
pub UNUSED_QUALIFICATIONS,
Allow,
"detects unnecessarily qualified names"
}
declare_lint! {
pub UNKNOWN_LINTS,
Warn,
"unrecognized lint attribute"
}
declare_lint! {
pub UNUSED_VARIABLES,
Warn,
"detect variables which are not used in any way"
}
declare_lint! {
pub UNUSED_ASSIGNMENTS,
Warn,
"detect assignments that will never be read"
}
declare_lint! {
pub DEAD_CODE,
Warn,
"detect unused, unexported items"
}
declare_lint! {
pub UNREACHABLE_CODE,
Warn,
"detects unreachable code paths"
}
declare_lint! {
pub WARNINGS,
Warn,
"mass-change the level for lints which produce warnings"
}
declare_lint! {
pub UNUSED_FEATURES,
Warn,
"unused or unknown features found in crate-level #[feature] directives"
}
declare_lint! {
pub STABLE_FEATURES,
Warn,
"stable features found in #[feature] directive"
}
declare_lint! {
pub UNKNOWN_CRATE_TYPES,
Deny,
"unknown crate type found in #[crate_type] directive"
}
declare_lint! {
pub VARIANT_SIZE_DIFFERENCES,
Allow,
"detects enums with widely varying variant sizes"
}
declare_lint! {
pub FAT_PTR_TRANSMUTES,
Allow,
"detects transmutes of fat pointers"
}
declare_lint! {
pub TRIVIAL_CASTS,
Allow,
"detects trivial casts which could be removed"
}
declare_lint! {
pub TRIVIAL_NUMERIC_CASTS,
Allow,
"detects trivial casts of numeric types which could be removed"
}
declare_lint! {
pub PRIVATE_IN_PUBLIC,
Warn,
"detect private items in public interfaces not caught by the old implementation"
}
declare_lint! {
pub INACCESSIBLE_EXTERN_CRATE,
Warn,
"use of inaccessible extern crate erroneously allowed"
}
declare_lint! {
pub INVALID_TYPE_PARAM_DEFAULT,
Warn,
"type parameter default erroneously allowed in invalid location"
}
declare_lint! {
pub ILLEGAL_FLOATING_POINT_CONSTANT_PATTERN,
Warn,
"floating-point constants cannot be used in patterns"
}
declare_lint! {
pub ILLEGAL_STRUCT_OR_ENUM_CONSTANT_PATTERN,
Deny,
"constants of struct or enum type can only be used in a pattern if \
the struct or enum has `#[derive(Eq)]`"
}
declare_lint! {
pub MATCH_OF_UNIT_VARIANT_VIA_PAREN_DOTDOT,
Deny,
"unit struct or enum variant erroneously allowed to match via path::ident(..)"
}
declare_lint! {
pub RAW_POINTER_DERIVE,
Warn,
"uses of #[derive] with raw pointers are rarely correct"
}
declare_lint! {
pub TRANSMUTE_FROM_FN_ITEM_TYPES,
Warn,
"transmute from function item type to pointer-sized type erroneously allowed"
}
declare_lint! {
pub OVERLAPPING_INHERENT_IMPLS,
Warn,
"two overlapping inherent impls define an item with the same name were erroneously allowed"
}
declare_lint! {
pub RENAMED_AND_REMOVED_LINTS,
Warn,
"lints that have been renamed or removed"
}
/// Does nothing as a lint pass, but registers some `Lint`s
/// which are used by other parts of the compiler.
#[derive(Copy, Clone)]
pub struct HardwiredLints;
impl LintPass for HardwiredLints {
fn get_lints(&self) -> LintArray {
lint_array!(
UNUSED_IMPORTS,
UNUSED_EXTERN_CRATES,
UNUSED_QUALIFICATIONS,
UNKNOWN_LINTS,
UNUSED_VARIABLES,
UNUSED_ASSIGNMENTS,
DEAD_CODE,
UNREACHABLE_CODE,
WARNINGS,
UNUSED_FEATURES,
STABLE_FEATURES,
UNKNOWN_CRATE_TYPES,
VARIANT_SIZE_DIFFERENCES,
FAT_PTR_TRANSMUTES,
TRIVIAL_CASTS,
TRIVIAL_NUMERIC_CASTS,
PRIVATE_IN_PUBLIC,
INACCESSIBLE_EXTERN_CRATE,
INVALID_TYPE_PARAM_DEFAULT,
ILLEGAL_FLOATING_POINT_CONSTANT_PATTERN,
ILLEGAL_STRUCT_OR_ENUM_CONSTANT_PATTERN,
MATCH_OF_UNIT_VARIANT_VIA_PAREN_DOTDOT,
CONST_ERR,
RAW_POINTER_DERIVE,
TRANSMUTE_FROM_FN_ITEM_TYPES,
OVERLAPPING_INHERENT_IMPLS,
RENAMED_AND_REMOVED_LINTS
)
}
}
impl LateLintPass for HardwiredLints {}