rust-clippy/clippy_lints/src/copies.rs

211 lines
5.9 KiB
Rust

use crate::utils::{eq_expr_value, in_macro, search_same, SpanlessEq, SpanlessHash};
use crate::utils::{get_parent_expr, if_sequence, span_lint_and_note};
use rustc_hir::{Block, Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// **What it does:** Checks for consecutive `if`s with the same condition.
///
/// **Why is this bad?** This is probably a copy & paste error.
///
/// **Known problems:** Hopefully none.
///
/// **Example:**
/// ```ignore
/// if a == b {
/// …
/// } else if a == b {
/// …
/// }
/// ```
///
/// Note that this lint ignores all conditions with a function call as it could
/// have side effects:
///
/// ```ignore
/// if foo() {
/// …
/// } else if foo() { // not linted
/// …
/// }
/// ```
pub IFS_SAME_COND,
correctness,
"consecutive `if`s with the same condition"
}
declare_clippy_lint! {
/// **What it does:** Checks for consecutive `if`s with the same function call.
///
/// **Why is this bad?** This is probably a copy & paste error.
/// Despite the fact that function can have side effects and `if` works as
/// intended, such an approach is implicit and can be considered a "code smell".
///
/// **Known problems:** Hopefully none.
///
/// **Example:**
/// ```ignore
/// if foo() == bar {
/// …
/// } else if foo() == bar {
/// …
/// }
/// ```
///
/// This probably should be:
/// ```ignore
/// if foo() == bar {
/// …
/// } else if foo() == baz {
/// …
/// }
/// ```
///
/// or if the original code was not a typo and called function mutates a state,
/// consider move the mutation out of the `if` condition to avoid similarity to
/// a copy & paste error:
///
/// ```ignore
/// let first = foo();
/// if first == bar {
/// …
/// } else {
/// let second = foo();
/// if second == bar {
/// …
/// }
/// }
/// ```
pub SAME_FUNCTIONS_IN_IF_CONDITION,
pedantic,
"consecutive `if`s with the same function call"
}
declare_clippy_lint! {
/// **What it does:** Checks for `if/else` with the same body as the *then* part
/// and the *else* part.
///
/// **Why is this bad?** This is probably a copy & paste error.
///
/// **Known problems:** Hopefully none.
///
/// **Example:**
/// ```ignore
/// let foo = if … {
/// 42
/// } else {
/// 42
/// };
/// ```
pub IF_SAME_THEN_ELSE,
correctness,
"`if` with the same `then` and `else` blocks"
}
declare_lint_pass!(CopyAndPaste => [IFS_SAME_COND, SAME_FUNCTIONS_IN_IF_CONDITION, IF_SAME_THEN_ELSE]);
impl<'tcx> LateLintPass<'tcx> for CopyAndPaste {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if !expr.span.from_expansion() {
// skip ifs directly in else, it will be checked in the parent if
if let Some(&Expr {
kind: ExprKind::If(_, _, Some(ref else_expr)),
..
}) = get_parent_expr(cx, expr)
{
if else_expr.hir_id == expr.hir_id {
return;
}
}
let (conds, blocks) = if_sequence(expr);
lint_same_then_else(cx, &blocks);
lint_same_cond(cx, &conds);
lint_same_fns_in_if_cond(cx, &conds);
}
}
}
/// Implementation of `IF_SAME_THEN_ELSE`.
fn lint_same_then_else(cx: &LateContext<'_>, blocks: &[&Block<'_>]) {
let eq: &dyn Fn(&&Block<'_>, &&Block<'_>) -> bool =
&|&lhs, &rhs| -> bool { SpanlessEq::new(cx).eq_block(lhs, rhs) };
if let Some((i, j)) = search_same_sequenced(blocks, eq) {
span_lint_and_note(
cx,
IF_SAME_THEN_ELSE,
j.span,
"this `if` has identical blocks",
Some(i.span),
"same as this",
);
}
}
/// Implementation of `IFS_SAME_COND`.
fn lint_same_cond(cx: &LateContext<'_>, conds: &[&Expr<'_>]) {
let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 {
let mut h = SpanlessHash::new(cx);
h.hash_expr(expr);
h.finish()
};
let eq: &dyn Fn(&&Expr<'_>, &&Expr<'_>) -> bool = &|&lhs, &rhs| -> bool { eq_expr_value(cx, lhs, rhs) };
for (i, j) in search_same(conds, hash, eq) {
span_lint_and_note(
cx,
IFS_SAME_COND,
j.span,
"this `if` has the same condition as a previous `if`",
Some(i.span),
"same as this",
);
}
}
/// Implementation of `SAME_FUNCTIONS_IN_IF_CONDITION`.
fn lint_same_fns_in_if_cond(cx: &LateContext<'_>, conds: &[&Expr<'_>]) {
let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 {
let mut h = SpanlessHash::new(cx);
h.hash_expr(expr);
h.finish()
};
let eq: &dyn Fn(&&Expr<'_>, &&Expr<'_>) -> bool = &|&lhs, &rhs| -> bool {
// Do not lint if any expr originates from a macro
if in_macro(lhs.span) || in_macro(rhs.span) {
return false;
}
// Do not spawn warning if `IFS_SAME_COND` already produced it.
if eq_expr_value(cx, lhs, rhs) {
return false;
}
SpanlessEq::new(cx).eq_expr(lhs, rhs)
};
for (i, j) in search_same(conds, hash, eq) {
span_lint_and_note(
cx,
SAME_FUNCTIONS_IN_IF_CONDITION,
j.span,
"this `if` has the same function call as a previous `if`",
Some(i.span),
"same as this",
);
}
}
fn search_same_sequenced<T, Eq>(exprs: &[T], eq: Eq) -> Option<(&T, &T)>
where
Eq: Fn(&T, &T) -> bool,
{
for win in exprs.windows(2) {
if eq(&win[0], &win[1]) {
return Some((&win[0], &win[1]));
}
}
None
}