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mod let_unit_value;
mod unit_arg;
mod unit_cmp;
mod utils;
use rustc_hir::{Expr, Local};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// ### What it does
/// Checks for binding a unit value.
///
/// ### Why is this bad?
/// A unit value cannot usefully be used anywhere. So
/// binding one is kind of pointless.
///
/// ### Example
/// ```rust
/// let x = {
/// 1;
/// };
/// ```
#[clippy::version = "pre 1.29.0"]
pub LET_UNIT_VALUE,
style,
"creating a `let` binding to a value of unit type, which usually can't be used afterwards"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for comparisons to unit. This includes all binary
/// comparisons (like `==` and `<`) and asserts.
///
/// ### Why is this bad?
/// Unit is always equal to itself, and thus is just a
/// clumsily written constant. Mostly this happens when someone accidentally
/// adds semicolons at the end of the operands.
///
/// ### Example
/// ```rust
/// # fn foo() {};
/// # fn bar() {};
/// # fn baz() {};
/// if {
/// foo();
/// } == {
/// bar();
/// } {
/// baz();
/// }
/// ```
/// is equal to
/// ```rust
/// # fn foo() {};
/// # fn bar() {};
/// # fn baz() {};
/// {
/// foo();
/// bar();
/// baz();
/// }
/// ```
///
/// For asserts:
/// ```rust
/// # fn foo() {};
/// # fn bar() {};
/// assert_eq!({ foo(); }, { bar(); });
/// ```
/// will always succeed
#[clippy::version = "pre 1.29.0"]
pub UNIT_CMP,
correctness,
"comparing unit values"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for passing a unit value as an argument to a function without using a
/// unit literal (`()`).
///
/// ### Why is this bad?
/// This is likely the result of an accidental semicolon.
///
/// ### Example
/// ```rust,ignore
/// foo({
/// let a = bar();
/// baz(a);
/// })
/// ```
#[clippy::version = "pre 1.29.0"]
pub UNIT_ARG,
complexity,
"passing unit to a function"
}
declare_lint_pass!(UnitTypes => [LET_UNIT_VALUE, UNIT_CMP, UNIT_ARG]);
impl<'tcx> LateLintPass<'tcx> for UnitTypes {
fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'tcx>) {
let_unit_value::check(cx, local);
}
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
unit_cmp::check(cx, expr);
unit_arg::check(cx, expr);
}
}
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