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suggest a op= b over a = a op b

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This commit is contained in:
Oliver Schneider
2016-05-11 15:32:20 +02:00
parent 855b292cda
commit c6b4b19a43
7 changed files with 234 additions and 3 deletions
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158
src/assign_ops.rs Normal file
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@@ -0,0 +1,158 @@
use rustc::hir;
use rustc::lint::*;
use utils::{span_lint_and_then, span_lint, snippet_opt, SpanlessEq, get_trait_def_id, implements_trait};
/// **What it does:** This lint checks for `+=` operations and similar
///
/// **Why is this bad?** Projects with many developers from languages without those operations
/// may find them unreadable and not worth their weight
///
/// **Known problems:** None
///
/// **Example:**
/// ```
/// a += 1;
/// ```
declare_restriction_lint! {
pub ASSIGN_OPS,
"Any assignment operation"
}
/// **What it does:** Check for `a = a op b` or `a = b commutative_op a` patterns
///
/// **Why is this bad?** These can be written as the shorter `a op= b`
///
/// **Known problems:** Hopefully none.
///
/// **Example:**
///
/// ```
/// let mut a = 5;
/// ...
/// a = a + b;
/// ```
declare_lint! {
pub ASSIGN_OP_PATTERN,
Warn,
"assigning the result of an operation on a variable to that same variable"
}
#[derive(Copy, Clone, Default)]
pub struct AssignOps;
impl LintPass for AssignOps {
fn get_lints(&self) -> LintArray {
lint_array!(ASSIGN_OPS, ASSIGN_OP_PATTERN)
}
}
impl LateLintPass for AssignOps {
fn check_expr(&mut self, cx: &LateContext, expr: &hir::Expr) {
match expr.node {
hir::ExprAssignOp(op, ref lhs, ref rhs) => {
if let (Some(l), Some(r)) = (snippet_opt(cx, lhs.span), snippet_opt(cx, rhs.span)) {
span_lint_and_then(cx,
ASSIGN_OPS,
expr.span,
"assign operation detected",
|db| {
match rhs.node {
hir::ExprBinary(op2, _, _) if op2 != op => {
db.span_suggestion(expr.span,
"replace it with",
format!("{} = {} {} ({})", l, l, op.node.as_str(), r));
},
_ => {
db.span_suggestion(expr.span,
"replace it with",
format!("{} = {} {} {}", l, l, op.node.as_str(), r));
}
}
});
} else {
span_lint(cx,
ASSIGN_OPS,
expr.span,
"assign operation detected");
}
},
hir::ExprAssign(ref assignee, ref e) => {
if let hir::ExprBinary(op, ref l, ref r) = e.node {
let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
let ty = cx.tcx.expr_ty(assignee);
if ty.walk_shallow().next().is_some() {
return; // implements_trait does not work with generics
}
let rty = cx.tcx.expr_ty(rhs);
if rty.walk_shallow().next().is_some() {
return; // implements_trait does not work with generics
}
macro_rules! ops {
($op:expr, $cx:expr, $ty:expr, $rty:expr, $($trait_name:ident:$full_trait_name:ident),+) => {
match $op {
$(hir::$full_trait_name => {
let [krate, module] = ::utils::paths::OPS_MODULE;
let path = [krate, module, concat!(stringify!($trait_name), "Assign")];
let trait_id = if let Some(trait_id) = get_trait_def_id($cx, &path) {
trait_id
} else {
return; // useless if the trait doesn't exist
};
implements_trait($cx, $ty, trait_id, vec![$rty])
},)*
_ => false,
}
}
}
if ops!(op.node, cx, ty, rty, Add:BiAdd,
Sub:BiSub,
Mul:BiMul,
Div:BiDiv,
Rem:BiRem,
And:BiAnd,
Or:BiOr,
BitAnd:BiBitAnd,
BitOr:BiBitOr,
BitXor:BiBitXor,
Shr:BiShr,
Shl:BiShl
) {
if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span)) {
span_lint_and_then(cx,
ASSIGN_OP_PATTERN,
expr.span,
"manual implementation of an assign operation",
|db| {
db.span_suggestion(expr.span,
"replace it with",
format!("{} {}= {}", snip_a, op.node.as_str(), snip_r));
});
} else {
span_lint(cx,
ASSIGN_OP_PATTERN,
expr.span,
"manual implementation of an assign operation");
}
}
};
// a = a op b
if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, l) {
lint(assignee, r);
}
// a = b commutative_op a
if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, r) {
match op.node {
hir::BiAdd | hir::BiMul |
hir::BiAnd | hir::BiOr |
hir::BiBitXor | hir::BiBitAnd | hir::BiBitOr => {
lint(assignee, l);
},
_ => {},
}
}
}
},
_ => {},
}
}
}

5
src/lib.rs
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@@ -7,7 +7,6 @@
#![feature(question_mark)]
#![feature(stmt_expr_attributes)]
#![allow(indexing_slicing, shadow_reuse, unknown_lints)]
#![allow(float_arithmetic, integer_arithmetic)]
extern crate rustc_driver;
extern crate getopts;
@@ -192,6 +191,7 @@ pub mod utils;
pub mod approx_const;
pub mod arithmetic;
pub mod array_indexing;
pub mod assign_ops;
pub mod attrs;
pub mod bit_mask;
pub mod blacklisted_name;
@@ -383,10 +383,12 @@ pub fn plugin_registrar(reg: &mut Registry) {
reg.register_late_lint_pass(box unsafe_removed_from_name::UnsafeNameRemoval);
reg.register_late_lint_pass(box mem_forget::MemForget);
reg.register_late_lint_pass(box arithmetic::Arithmetic::default());
reg.register_late_lint_pass(box assign_ops::AssignOps);
reg.register_lint_group("clippy_restrictions", vec![
arithmetic::FLOAT_ARITHMETIC,
arithmetic::INTEGER_ARITHMETIC,
assign_ops::ASSIGN_OPS,
]);
reg.register_lint_group("clippy_pedantic", vec![
@@ -421,6 +423,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
reg.register_lint_group("clippy", vec![
approx_const::APPROX_CONSTANT,
array_indexing::OUT_OF_BOUNDS_INDEXING,
assign_ops::ASSIGN_OP_PATTERN,
attrs::DEPRECATED_SEMVER,
attrs::INLINE_ALWAYS,
bit_mask::BAD_BIT_MASK,

1
src/utils/paths.rs
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@@ -29,6 +29,7 @@ pub const LINKED_LIST: [&'static str; 3] = ["collections", "linked_list", "Linke
pub const MEM_FORGET: [&'static str; 3] = ["core", "mem", "forget"];
pub const MUTEX: [&'static str; 4] = ["std", "sync", "mutex", "Mutex"];
pub const OPEN_OPTIONS: [&'static str; 3] = ["std", "fs", "OpenOptions"];
pub const OPS_MODULE: [&'static str; 2] = ["core", "ops"];
pub const OPTION: [&'static str; 3] = ["core", "option", "Option"];
pub const RANGE: [&'static str; 3] = ["core", "ops", "Range"];
pub const RANGE_FROM: [&'static str; 3] = ["core", "ops", "RangeFrom"];