diff --git a/README.md b/README.md index 4c23d6994..5a2ea9453 100644 --- a/README.md +++ b/README.md @@ -6,7 +6,7 @@ A collection of lints to catch common mistakes and improve your Rust code. [Jump to usage instructions](#usage) ##Lints -There are 72 lints included in this crate: +There are 73 lints included in this crate: name | default | meaning -------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ @@ -68,6 +68,7 @@ name [string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add) | allow | using `x + ..` where x is a `String`; suggests using `push_str()` instead [string_add_assign](https://github.com/Manishearth/rust-clippy/wiki#string_add_assign) | allow | using `x = x + ..` where x is a `String`; suggests using `push_str()` instead [string_to_string](https://github.com/Manishearth/rust-clippy/wiki#string_to_string) | warn | calling `String.to_string()` which is a no-op +[temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment) | warn | assignments to temporaries [toplevel_ref_arg](https://github.com/Manishearth/rust-clippy/wiki#toplevel_ref_arg) | warn | An entire binding was declared as `ref`, in a function argument (`fn foo(ref x: Bar)`), or a `let` statement (`let ref x = foo()`). In such cases, it is preferred to take references with `&`. [type_complexity](https://github.com/Manishearth/rust-clippy/wiki#type_complexity) | warn | usage of very complex types; recommends factoring out parts into `type` definitions [unicode_not_nfc](https://github.com/Manishearth/rust-clippy/wiki#unicode_not_nfc) | allow | using a unicode literal not in NFC normal form (see http://www.unicode.org/reports/tr15/ for further information) diff --git a/src/lib.rs b/src/lib.rs index 37e1ace61..970a244e2 100755 --- a/src/lib.rs +++ b/src/lib.rs @@ -54,6 +54,7 @@ pub mod open_options; pub mod needless_features; pub mod needless_update; pub mod no_effect; +pub mod temporary_assignment; mod reexport { pub use syntax::ast::{Name, Ident, NodeId}; @@ -102,6 +103,7 @@ pub fn plugin_registrar(reg: &mut Registry) { reg.register_late_lint_pass(box needless_update::NeedlessUpdatePass); reg.register_late_lint_pass(box no_effect::NoEffectPass); reg.register_late_lint_pass(box map_clone::MapClonePass); + reg.register_late_lint_pass(box temporary_assignment::TemporaryAssignmentPass); reg.register_lint_group("clippy_pedantic", vec![ methods::OPTION_UNWRAP_USED, @@ -172,6 +174,7 @@ pub fn plugin_registrar(reg: &mut Registry) { ranges::RANGE_ZIP_WITH_LEN, returns::LET_AND_RETURN, returns::NEEDLESS_RETURN, + temporary_assignment::TEMPORARY_ASSIGNMENT, types::BOX_VEC, types::LET_UNIT_VALUE, types::LINKEDLIST, diff --git a/src/temporary_assignment.rs b/src/temporary_assignment.rs new file mode 100644 index 000000000..6cfcb711f --- /dev/null +++ b/src/temporary_assignment.rs @@ -0,0 +1,44 @@ +use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; +use rustc_front::hir::{Expr, ExprAssign, ExprField, ExprStruct, ExprTup, ExprTupField}; + +use utils::is_adjusted; +use utils::span_lint; + +declare_lint! { + pub TEMPORARY_ASSIGNMENT, + Warn, + "assignments to temporaries" +} + +fn is_temporary(expr: &Expr) -> bool { + match expr.node { + ExprStruct(..) | + ExprTup(..) => true, + _ => false, + } +} + +#[derive(Copy, Clone)] +pub struct TemporaryAssignmentPass; + +impl LintPass for TemporaryAssignmentPass { + fn get_lints(&self) -> LintArray { + lint_array!(TEMPORARY_ASSIGNMENT) + } +} + +impl LateLintPass for TemporaryAssignmentPass { + fn check_expr(&mut self, cx: &LateContext, expr: &Expr) { + if let ExprAssign(ref target, _) = expr.node { + match target.node { + ExprField(ref base, _) | ExprTupField(ref base, _) => { + if is_temporary(base) && !is_adjusted(cx, base) { + span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, + "assignment to temporary"); + } + } + _ => () + } + } + } +} diff --git a/tests/compile-fail/temporary_assignment.rs b/tests/compile-fail/temporary_assignment.rs new file mode 100644 index 000000000..b1c2b9900 --- /dev/null +++ b/tests/compile-fail/temporary_assignment.rs @@ -0,0 +1,36 @@ +#![feature(plugin)] +#![plugin(clippy)] + +#![deny(temporary_assignment)] + +use std::ops::{Deref, DerefMut}; + +struct Struct { + field: i32 +} + +struct Wrapper<'a> { + inner: &'a mut Struct +} + +impl<'a> Deref for Wrapper<'a> { + type Target = Struct; + fn deref(&self) -> &Struct { self.inner } +} + +impl<'a> DerefMut for Wrapper<'a> { + fn deref_mut(&mut self) -> &mut Struct { self.inner } +} + +fn main() { + let mut s = Struct { field: 0 }; + let mut t = (0, 0); + + Struct { field: 0 }.field = 1; //~ERROR assignment to temporary + (0, 0).0 = 1; //~ERROR assignment to temporary + + // no error + s.field = 1; + t.0 = 1; + Wrapper { inner: &mut s }.field = 1; +}