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Enhance manual flatten

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This commit is contained in:
nahuakang 2021-02-02 19:04:20 +01:00
parent b87e189694
commit e07cd5b6fe
3 changed files with 104 additions and 71 deletions
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76
clippy_lints/src/loops.rs
View file

@ -1996,11 +1996,23 @@ fn check_manual_flatten<'tcx>(
body: &'tcx Expr<'_>,
span: Span,
) {
if let ExprKind::Block(ref block, _) = body.kind {
// Ensure the `if let` statement is the only expression or statement in the for-loop
let inner_expr = if block.stmts.len() == 1 && block.expr.is_none() {
let match_stmt = &block.stmts[0];
if let StmtKind::Semi(inner_expr) = match_stmt.kind {
Some(inner_expr)
} else {
None
}
} else if block.stmts.is_empty() {
block.expr
} else {
None
};
if_chain! {
// Ensure the `if let` statement is the only expression in the for-loop
if let ExprKind::Block(ref block, _) = body.kind;
if block.stmts.is_empty();
if let Some(inner_expr) = block.expr;
if let Some(inner_expr) = inner_expr;
if let ExprKind::Match(
ref match_expr, ref match_arms, MatchSource::IfLetDesugar{ contains_else_clause: false }
) = inner_expr.kind;
@ -2011,37 +2023,55 @@ fn check_manual_flatten<'tcx>(
if pat_hir_id == match_expr_path_id;
// Ensure the `if let` statement is for the `Some` variant of `Option` or the `Ok` variant of `Result`
if let PatKind::TupleStruct(QPath::Resolved(None, path), _, _) = match_arms[0].pat.kind;
if is_some_ctor(cx, path.res) || is_ok_ctor(cx, path.res);
let if_let_type = if is_some_ctor(cx, path.res) {
"Some"
} else {
"Ok"
};
// Determine if `arg` is `Iterator` or implicitly calls `into_iter`
let arg_ty = cx.typeck_results().expr_ty(arg);
if let Some(id) = get_trait_def_id(cx, &paths::ITERATOR);
if let is_iterator = implements_trait(cx, arg_ty, id, &[]);
let some_ctor = is_some_ctor(cx, path.res);
let ok_ctor = is_ok_ctor(cx, path.res);
if some_ctor || ok_ctor;
let if_let_type = if some_ctor { "Some" } else { "Ok" };
then {
// Prepare the error message
let msg = format!("Unnecessary `if let` since only the `{}` variant of the iterator element is used.", if_let_type);
let msg = format!("unnecessary `if let` since only the `{}` variant of the iterator element is used", if_let_type);
// Prepare the help message
let arg_snippet = snippet(cx, arg.span, "..");
let hint = if is_iterator {
format!("try: `{}.flatten()`", arg_snippet)
let mut applicability = Applicability::MaybeIncorrect;
let arg_snippet = snippet_with_applicability(
cx,
arg.span,
"..",
&mut applicability,
);
// Determine if `arg` is by reference, an `Iterator`, or implicitly adjusted with `into_iter`
let hint = match arg.kind {
ExprKind::AddrOf(_, _, arg_expr) => {
format!("{}.iter().flatten()", snippet(cx, arg_expr.span, ".."))
},
ExprKind::MethodCall(_, _, _, _) | ExprKind::Path(QPath::Resolved(None, _)) => {
// Determine if `arg` is `Iterator` or implicitly calls `into_iter`
let arg_ty = cx.typeck_results().expr_ty(arg);
if let Some(id) = get_trait_def_id(cx, &paths::ITERATOR) {
let is_iterator = implements_trait(cx, arg_ty, id, &[]);
if is_iterator {
format!("{}.flatten()", arg_snippet)
} else {
format!("try: `{}.into_iter().flatten()`", arg_snippet)
format!("{}.into_iter().flatten()", arg_snippet)
}
} else {
return
}
},
_ => return,
};
span_lint_and_help(
span_lint_and_sugg(
cx,
MANUAL_FLATTEN,
span,
&msg,
Some(arg.span),
&hint,
);
"try",
hint,
applicability,
)
}
}
}
}

10
tests/ui/manual_flatten.rs
View file

@ -1,6 +1,7 @@
#![warn(clippy::manual_flatten)]
fn main() {
// Test for loop over implicitly adjusted `Iterator` with `if let` expression
let x = vec![Some(1), Some(2), Some(3)];
for n in x {
if let Some(n) = n {
@ -8,13 +9,22 @@ fn main() {
}
}
// Test for loop over implicitly implicitly adjusted `Iterator` with `if let` statement
let y: Vec<Result<i32, i32>> = vec![];
for n in y.clone() {
if let Ok(n) = n {
println!("{}", n);
};
}
// Test for loop over by reference
for n in &y {
if let Ok(n) = n {
println!("{}", n);
}
}
// Test for loop over `Iterator` with `if let` expression
let z = vec![Some(1), Some(2), Some(3)];
let z = z.iter();
for n in z {

49
tests/ui/manual_flatten.stderr
View file

@ -1,51 +1,44 @@
error: Unnecessary `if let` since only the `Some` variant of the iterator element is used.
--> $DIR/manual_flatten.rs:5:5
error: unnecessary `if let` since only the `Some` variant of the iterator element is used
--> $DIR/manual_flatten.rs:6:5
|
LL | / for n in x {
LL | | if let Some(n) = n {
LL | | println!("{}", n);
LL | | }
LL | | }
| |_____^
| |_____^ help: try: `x.into_iter().flatten()`
|
= note: `-D clippy::manual-flatten` implied by `-D warnings`
help: try: `x.into_iter().flatten()`
--> $DIR/manual_flatten.rs:5:14
|
LL | for n in x {
| ^
error: Unnecessary `if let` since only the `Ok` variant of the iterator element is used.
--> $DIR/manual_flatten.rs:12:5
error: unnecessary `if let` since only the `Ok` variant of the iterator element is used
--> $DIR/manual_flatten.rs:14:5
|
LL | / for n in y.clone() {
LL | | if let Ok(n) = n {
LL | | println!("{}", n);
LL | | };
LL | | }
LL | | }
| |_____^
|
help: try: `y.clone().into_iter().flatten()`
--> $DIR/manual_flatten.rs:12:14
|
LL | for n in y.clone() {
| ^^^^^^^^^
| |_____^ help: try: `y.clone().into_iter().flatten()`
error: Unnecessary `if let` since only the `Some` variant of the iterator element is used.
--> $DIR/manual_flatten.rs:20:5
error: unnecessary `if let` since only the `Ok` variant of the iterator element is used
--> $DIR/manual_flatten.rs:21:5
|
LL | / for n in &y {
LL | | if let Ok(n) = n {
LL | | println!("{}", n);
LL | | }
LL | | }
| |_____^ help: try: `y.iter().flatten()`
error: unnecessary `if let` since only the `Some` variant of the iterator element is used
--> $DIR/manual_flatten.rs:30:5
|
LL | / for n in z {
LL | | if let Some(n) = n {
LL | | println!("{}", n);
LL | | }
LL | | }
| |_____^
|
help: try: `z.flatten()`
--> $DIR/manual_flatten.rs:20:14
|
LL | for n in z {
| ^
| |_____^ help: try: `z.flatten()`
error: aborting due to 3 previous errors
error: aborting due to 4 previous errors