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;
+
+ then {
+ let right_source = snippet(cx, right_expr.span, "EXPR");
- // Span containing `.fold(...)`
- let fold_span = fold_args[0].span.next_point().with_hi(fold_args[2].span.hi() + BytePos(1));
+ // 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 .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_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) {
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);
-/// 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);
-}
+ // 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);
-/// 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 });
+ // Can be replaced by .product
+ let _ = (0..3).fold(1, |acc, x| acc * x);
+ let _ = (0..3).fold(1, |acc, x| x * acc);
}
-/// 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);
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`
projects / rust.git / commitdiff