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Lint on folds implementing .all, .sum and .product

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This commit is contained in:
Phil Ellison 2018-01-17 19:12:44 +00:00
parent a64d19cc0e
commit 1cac693bc7
3 changed files with 113 additions and 55 deletions
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93
clippy_lints/src/methods.rs
View file

@ -1134,47 +1134,74 @@ fn lint_fold_any(cx: &LateContext, expr: &hir::Expr, fold_args: &[hir::Expr]) {
assert!(fold_args.len() == 3,
"Expected fold_args to have three entries - the receiver, the initial value and the closure");
if_chain! {
// Check if the initial value for the fold is the literal `false`
if let hir::ExprLit(ref lit) = fold_args[1].node;
if lit.node == ast::LitKind::Bool(false);
fn check_fold_with_op(
cx: &LateContext,
fold_args: &[hir::Expr],
op: hir::BinOp_,
replacement_method_name: &str) {
// Extract the body of the closure passed to fold
if let hir::ExprClosure(_, _, body_id, _, _) = fold_args[2].node;
let closure_body = cx.tcx.hir.body(body_id);
let closure_expr = remove_blocks(&closure_body.value);
if_chain! {
// Extract the body of the closure passed to fold
if let hir::ExprClosure(_, _, body_id, _, _) = fold_args[2].node;
let closure_body = cx.tcx.hir.body(body_id);
let closure_expr = remove_blocks(&closure_body.value);
// Extract the names of the two arguments to the closure
if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
// Check if the closure body is of the form `acc <op> some_expr(x)`
if let hir::ExprBinary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
if bin_op.node == op;
// Check if the closure body is of the form `acc || some_expr(x)`
if let hir::ExprBinary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
if bin_op.node == hir::BinOp_::BiOr;
if let hir::ExprPath(hir::QPath::Resolved(None, ref path)) = left_expr.node;
if path.segments.len() == 1 && &path.segments[0].name == &first_arg_ident;
// Extract the names of the two arguments to the closure
if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
then {
let right_source = snippet(cx, right_expr.span, "EXPR");
if let hir::ExprPath(hir::QPath::Resolved(None, ref path)) = left_expr.node;
if path.segments.len() == 1 && &path.segments[0].name == &first_arg_ident;
// Span containing `.fold(...)`
let fold_span = fold_args[0].span.next_point().with_hi(fold_args[2].span.hi() + BytePos(1));
then {
let right_source = snippet(cx, right_expr.span, "EXPR");
span_lint_and_sugg(
cx,
FOLD_ANY,
fold_span,
// TODO: don't suggest .any(|x| f(x)) if we can suggest .any(f)
"this `.fold` can more succintly be expressed as `.any`",
"try",
format!(
".any(|{s}| {r})",
s = second_arg_ident,
r = right_source
)
);
// Span containing `.fold(...)`
let fold_span = fold_args[0].span.next_point().with_hi(fold_args[2].span.hi() + BytePos(1));
span_lint_and_sugg(
cx,
FOLD_ANY,
fold_span,
// TODO: don't suggest e.g. .any(|x| f(x)) if we can suggest .any(f)
"this `.fold` can be written more succinctly using another method",
"try",
format!(
".{replacement}(|{s}| {r})",
replacement = replacement_method_name,
s = second_arg_ident,
r = right_source
)
);
}
}
}
// Check if the first argument to .fold is a suitable literal
match fold_args[1].node {
hir::ExprLit(ref lit) => {
match lit.node {
ast::LitKind::Bool(false) => check_fold_with_op(
cx, fold_args, hir::BinOp_::BiOr, "any"
),
ast::LitKind::Bool(true) => check_fold_with_op(
cx, fold_args, hir::BinOp_::BiAnd, "all"
),
ast::LitKind::Int(0, _) => check_fold_with_op(
cx, fold_args, hir::BinOp_::BiAdd, "sum"
),
ast::LitKind::Int(1, _) => check_fold_with_op(
cx, fold_args, hir::BinOp_::BiMul, "product"
),
_ => return
}
}
_ => return
};
}
fn lint_iter_nth(cx: &LateContext, expr: &hir::Expr, iter_args: &[hir::Expr], is_mut: bool) {

41
tests/ui/methods.rs
View file

@ -385,26 +385,39 @@ fn iter_skip_next() {
let _ = foo.filter().skip(42).next();
}
/// Should trigger the `FOLD_ANY` lint
fn fold_any() {
/// Calls which should trigger the `UNNECESSARY_FOLD` lint
fn unnecessary_fold() {
// Can be replaced by .any
let _ = (0..3).fold(false, |acc, x| acc || x > 2);
let _ = (0..3).fold(false, |acc, x| x > 2 || acc);
// Can be replaced by .all
let _ = (0..3).fold(true, |acc, x| acc && x > 2);
let _ = (0..3).fold(true, |acc, x| x > 2 && acc);
// Can be replaced by .sum
let _ = (0..3).fold(0, |acc, x| acc + x);
let _ = (0..3).fold(0, |acc, x| x + acc);
// Can be replaced by .product
let _ = (0..3).fold(1, |acc, x| acc * x);
let _ = (0..3).fold(1, |acc, x| x * acc);
}
/// Should not trigger the `FOLD_ANY` lint as the initial value is not the literal `false`
fn fold_any_ignores_initial_value_of_true() {
let _ = (0..3).fold(true, |acc, x| acc || x > 2);
}
/// Should not trigger the `FOLD_ANY` lint as the accumulator is not integer valued
fn fold_any_ignores_non_boolean_accumalator() {
let _ = (0..3).fold(0, |acc, x| acc + if x > 2 { 1 } else { 0 });
}
/// Should trigger the `FOLD_ANY` lint, with the error span including exactly `.fold(...)`
fn fold_any_span_for_multi_element_chain() {
/// Should trigger the `UNNECESSARY_FOLD` lint, with an error span including exactly `.fold(...)`
fn unnecessary_fold_span_for_multi_element_chain() {
let _ = (0..3).map(|x| 2 * x).fold(false, |acc, x| acc || x > 2);
}
/// Calls which should not trigger the `UNNECESSARY_FOLD` lint
fn unnecessary_fold_should_ignore() {
let _ = (0..3).fold(true, |acc, x| acc || x > 2);
let _ = (0..3).fold(false, |acc, x| acc && x > 2);
let _ = (0..3).fold(1, |acc, x| acc + x);
let _ = (0..3).fold(0, |acc, x| acc * x);
let _ = (0..3).fold(0, |acc, x| 1 + acc + x);
}
#[allow(similar_names)]
fn main() {
let opt = Some(0);

34
tests/ui/methods.stderr
View file

@ -493,24 +493,42 @@ error: called `skip(x).next()` on an iterator. This is more succinctly expressed
382 | let _ = &some_vec[..].iter().skip(3).next();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: this `.fold` can more succintly be expressed as `.any`
--> $DIR/methods.rs:390:19
error: this `.fold` can be written more succinctly using another method
--> $DIR/methods.rs:391:19
|
390 | let _ = (0..3).fold(false, |acc, x| acc || x > 2);
391 | let _ = (0..3).fold(false, |acc, x| acc || x > 2);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.any(|x| x > 2)`
|
= note: `-D fold-any` implied by `-D warnings`
error: this `.fold` can more succintly be expressed as `.any`
--> $DIR/methods.rs:405:34
error: this `.fold` can be written more succinctly using another method
--> $DIR/methods.rs:395:19
|
405 | let _ = (0..3).map(|x| 2 * x).fold(false, |acc, x| acc || x > 2);
395 | let _ = (0..3).fold(true, |acc, x| acc && x > 2);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.all(|x| x > 2)`
error: this `.fold` can be written more succinctly using another method
--> $DIR/methods.rs:399:19
|
399 | let _ = (0..3).fold(0, |acc, x| acc + x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.sum(|x| x)`
error: this `.fold` can be written more succinctly using another method
--> $DIR/methods.rs:403:19
|
403 | let _ = (0..3).fold(1, |acc, x| acc * x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.product(|x| x)`
error: this `.fold` can be written more succinctly using another method
--> $DIR/methods.rs:409:34
|
409 | let _ = (0..3).map(|x| 2 * x).fold(false, |acc, x| acc || x > 2);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.any(|x| x > 2)`
error: used unwrap() on an Option value. If you don't want to handle the None case gracefully, consider using expect() to provide a better panic message
--> $DIR/methods.rs:411:13
--> $DIR/methods.rs:424:13
|
411 | let _ = opt.unwrap();
424 | let _ = opt.unwrap();
| ^^^^^^^^^^^^
|
= note: `-D option-unwrap-used` implied by `-D warnings`