use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::sugg::Sugg;
-use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::usage::contains_return_break_continue_macro;
-use clippy_utils::{eager_or_lazy, in_macro, is_else_clause, is_lang_ctor};
+use clippy_utils::{
+ can_move_expr_to_closure, eager_or_lazy, higher, in_constant, is_else_clause, is_res_lang_ctor, peel_blocks,
+ peel_hir_expr_while, CaptureKind,
+};
use if_chain::if_chain;
use rustc_errors::Applicability;
-use rustc_hir::LangItem::OptionSome;
-use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, MatchSource, Mutability, PatKind, UnOp};
+use rustc_hir::LangItem::{OptionNone, OptionSome, ResultErr, ResultOk};
+use rustc_hir::{
+ def::Res, Arm, BindingAnnotation, Expr, ExprKind, MatchSource, Mutability, Pat, PatKind, Path, QPath, UnOp,
+};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
-use rustc_span::sym;
declare_clippy_lint! {
- /// **What it does:**
- /// Lints usage of `if let Some(v) = ... { y } else { x }` which is more
+ /// ### What it does
+ /// Lints usage of `if let Some(v) = ... { y } else { x }` and
+ /// `match .. { Some(v) => y, None/_ => x }` which are more
/// idiomatically done with `Option::map_or` (if the else bit is a pure
/// expression) or `Option::map_or_else` (if the else bit is an impure
/// expression).
///
- /// **Why is this bad?**
- /// Using the dedicated functions of the Option type is clearer and
+ /// ### Why is this bad?
+ /// Using the dedicated functions of the `Option` type is clearer and
/// more concise than an `if let` expression.
///
- /// **Known problems:**
+ /// ### Known problems
/// This lint uses a deliberately conservative metric for checking
/// if the inside of either body contains breaks or continues which will
/// cause it to not suggest a fix if either block contains a loop with
/// continues or breaks contained within the loop.
///
- /// **Example:**
- ///
+ /// ### Example
/// ```rust
/// # let optional: Option<u32> = Some(0);
/// # fn do_complicated_function() -> u32 { 5 };
/// } else {
/// 5
/// };
+ /// let _ = match optional {
+ /// Some(val) => val + 1,
+ /// None => 5
+ /// };
/// let _ = if let Some(foo) = optional {
/// foo
/// } else {
/// # let optional: Option<u32> = Some(0);
/// # fn do_complicated_function() -> u32 { 5 };
/// let _ = optional.map_or(5, |foo| foo);
+ /// let _ = optional.map_or(5, |val| val + 1);
/// let _ = optional.map_or_else(||{
/// let y = do_complicated_function();
/// y*y
/// }, |foo| foo);
/// ```
+ // FIXME: Before moving this lint out of nursery, the lint name needs to be updated. It now also
+ // covers matches and `Result`.
+ #[clippy::version = "1.47.0"]
pub OPTION_IF_LET_ELSE,
- pedantic,
+ nursery,
"reimplementation of Option::map_or"
}
declare_lint_pass!(OptionIfLetElse => [OPTION_IF_LET_ELSE]);
-/// Returns true iff the given expression is the result of calling `Result::ok`
-fn is_result_ok(cx: &LateContext<'_>, expr: &'_ Expr<'_>) -> bool {
- if let ExprKind::MethodCall(path, _, &[ref receiver], _) = &expr.kind {
- path.ident.name.as_str() == "ok"
- && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(receiver), sym::result_type)
- } else {
- false
- }
-}
-
-/// A struct containing information about occurrences of the
-/// `if let Some(..) = .. else` construct that this lint detects.
-struct OptionIfLetElseOccurence {
+/// A struct containing information about occurrences of construct that this lint detects
+///
+/// Such as:
+///
+/// ```ignore
+/// if let Some(..) = {..} else {..}
+/// ```
+/// or
+/// ```ignore
+/// match x {
+/// Some(..) => {..},
+/// None/_ => {..}
+/// }
+/// ```
+struct OptionOccurrence {
option: String,
method_sugg: String,
some_expr: String,
none_expr: String,
}
-/// Extracts the body of a given arm. If the arm contains only an expression,
-/// then it returns the expression. Otherwise, it returns the entire block
-fn extract_body_from_arm<'a>(arm: &'a Arm<'a>) -> Option<&'a Expr<'a>> {
- if let ExprKind::Block(
- Block {
- stmts: statements,
- expr: Some(expr),
- ..
- },
- _,
- ) = &arm.body.kind
- {
- if let [] = statements {
- Some(expr)
- } else {
- Some(arm.body)
- }
- } else {
- None
- }
-}
-
fn format_option_in_sugg(cx: &LateContext<'_>, cond_expr: &Expr<'_>, as_ref: bool, as_mut: bool) -> String {
format!(
"{}{}",
- Sugg::hir(cx, cond_expr, "..").maybe_par(),
+ Sugg::hir_with_macro_callsite(cx, cond_expr, "..").maybe_par(),
if as_mut {
".as_mut()"
} else if as_ref {
)
}
-/// If this expression is the option if let/else construct we're detecting, then
-/// this function returns an `OptionIfLetElseOccurence` struct with details if
-/// this construct is found, or None if this construct is not found.
-fn detect_option_if_let_else<'tcx>(
- cx: &'_ LateContext<'tcx>,
- expr: &'_ Expr<'tcx>,
-) -> Option<OptionIfLetElseOccurence> {
+fn try_get_option_occurrence<'tcx>(
+ cx: &LateContext<'tcx>,
+ pat: &Pat<'tcx>,
+ expr: &Expr<'_>,
+ if_then: &'tcx Expr<'_>,
+ if_else: &'tcx Expr<'_>,
+) -> Option<OptionOccurrence> {
+ let cond_expr = match expr.kind {
+ ExprKind::Unary(UnOp::Deref, inner_expr) | ExprKind::AddrOf(_, _, inner_expr) => inner_expr,
+ _ => expr,
+ };
+ let inner_pat = try_get_inner_pat(cx, pat)?;
if_chain! {
- if !in_macro(expr.span); // Don't lint macros, because it behaves weirdly
- if let ExprKind::Match(cond_expr, arms, MatchSource::IfLetDesugar{contains_else_clause: true}) = &expr.kind;
- if !is_else_clause(cx.tcx, expr);
- if arms.len() == 2;
- if !is_result_ok(cx, cond_expr); // Don't lint on Result::ok because a different lint does it already
- if let PatKind::TupleStruct(struct_qpath, &[inner_pat], _) = &arms[0].pat.kind;
- if is_lang_ctor(cx, struct_qpath, OptionSome);
- if let PatKind::Binding(bind_annotation, _, id, _) = &inner_pat.kind;
- if !contains_return_break_continue_macro(arms[0].body);
- if !contains_return_break_continue_macro(arms[1].body);
-
+ if let PatKind::Binding(bind_annotation, _, id, None) = inner_pat.kind;
+ if let Some(some_captures) = can_move_expr_to_closure(cx, if_then);
+ if let Some(none_captures) = can_move_expr_to_closure(cx, if_else);
+ if some_captures
+ .iter()
+ .filter_map(|(id, &c)| none_captures.get(id).map(|&c2| (c, c2)))
+ .all(|(x, y)| x.is_imm_ref() && y.is_imm_ref());
then {
- let capture_mut = if bind_annotation == &BindingAnnotation::Mutable { "mut " } else { "" };
- let some_body = extract_body_from_arm(&arms[0])?;
- let none_body = extract_body_from_arm(&arms[1])?;
- let method_sugg = if eager_or_lazy::is_eagerness_candidate(cx, none_body) { "map_or" } else { "map_or_else" };
+ let capture_mut = if bind_annotation == BindingAnnotation::MUT { "mut " } else { "" };
+ let some_body = peel_blocks(if_then);
+ let none_body = peel_blocks(if_else);
+ let method_sugg = if eager_or_lazy::switch_to_eager_eval(cx, none_body) { "map_or" } else { "map_or_else" };
let capture_name = id.name.to_ident_string();
- let (as_ref, as_mut) = match &cond_expr.kind {
+ let (as_ref, as_mut) = match &expr.kind {
ExprKind::AddrOf(_, Mutability::Not, _) => (true, false),
ExprKind::AddrOf(_, Mutability::Mut, _) => (false, true),
- _ => (bind_annotation == &BindingAnnotation::Ref, bind_annotation == &BindingAnnotation::RefMut),
+ _ => (bind_annotation == BindingAnnotation::REF, bind_annotation == BindingAnnotation::REF_MUT),
};
- let cond_expr = match &cond_expr.kind {
- // Pointer dereferencing happens automatically, so we can omit it in the suggestion
- ExprKind::Unary(UnOp::Deref, expr) | ExprKind::AddrOf(_, _, expr) => expr,
- _ => cond_expr,
- };
- Some(OptionIfLetElseOccurence {
+
+ // Check if captures the closure will need conflict with borrows made in the scrutinee.
+ // TODO: check all the references made in the scrutinee expression. This will require interacting
+ // with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
+ if as_ref || as_mut {
+ let e = peel_hir_expr_while(cond_expr, |e| match e.kind {
+ ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
+ _ => None,
+ });
+ if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(local_id), .. })) = e.kind {
+ match some_captures.get(local_id)
+ .or_else(|| (method_sugg == "map_or_else").then_some(()).and_then(|_| none_captures.get(local_id)))
+ {
+ Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return None,
+ Some(CaptureKind::Ref(Mutability::Not)) if as_mut => return None,
+ Some(CaptureKind::Ref(Mutability::Not)) | None => (),
+ }
+ }
+ }
+
+ return Some(OptionOccurrence {
option: format_option_in_sugg(cx, cond_expr, as_ref, as_mut),
method_sugg: method_sugg.to_string(),
- some_expr: format!("|{}{}| {}", capture_mut, capture_name, Sugg::hir(cx, some_body, "..")),
- none_expr: format!("{}{}", if method_sugg == "map_or" { "" } else { "|| " }, Sugg::hir(cx, none_body, "..")),
- })
+ some_expr: format!("|{capture_mut}{capture_name}| {}", Sugg::hir_with_macro_callsite(cx, some_body, "..")),
+ none_expr: format!("{}{}", if method_sugg == "map_or" { "" } else { "|| " }, Sugg::hir_with_macro_callsite(cx, none_body, "..")),
+ });
+ }
+ }
+
+ None
+}
+
+fn try_get_inner_pat<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'tcx>) -> Option<&'tcx Pat<'tcx>> {
+ if let PatKind::TupleStruct(ref qpath, [inner_pat], ..) = pat.kind {
+ let res = cx.qpath_res(qpath, pat.hir_id);
+ if is_res_lang_ctor(cx, res, OptionSome) || is_res_lang_ctor(cx, res, ResultOk) {
+ return Some(inner_pat);
+ }
+ }
+ None
+}
+
+/// If this expression is the option if let/else construct we're detecting, then
+/// this function returns an `OptionOccurrence` struct with details if
+/// this construct is found, or None if this construct is not found.
+fn detect_option_if_let_else<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> Option<OptionOccurrence> {
+ if let Some(higher::IfLet {
+ let_pat,
+ let_expr,
+ if_then,
+ if_else: Some(if_else),
+ }) = higher::IfLet::hir(cx, expr)
+ {
+ if !is_else_clause(cx.tcx, expr) {
+ return try_get_option_occurrence(cx, let_pat, let_expr, if_then, if_else);
+ }
+ }
+ None
+}
+
+fn detect_option_match<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> Option<OptionOccurrence> {
+ if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind {
+ if let Some((let_pat, if_then, if_else)) = try_convert_match(cx, arms) {
+ return try_get_option_occurrence(cx, let_pat, ex, if_then, if_else);
+ }
+ }
+ None
+}
+
+fn try_convert_match<'tcx>(
+ cx: &LateContext<'tcx>,
+ arms: &[Arm<'tcx>],
+) -> Option<(&'tcx Pat<'tcx>, &'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
+ if arms.len() == 2 {
+ return if is_none_or_err_arm(cx, &arms[1]) {
+ Some((arms[0].pat, arms[0].body, arms[1].body))
+ } else if is_none_or_err_arm(cx, &arms[0]) {
+ Some((arms[1].pat, arms[1].body, arms[0].body))
} else {
None
- }
+ };
+ }
+ None
+}
+
+fn is_none_or_err_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
+ match arm.pat.kind {
+ PatKind::Path(ref qpath) => is_res_lang_ctor(cx, cx.qpath_res(qpath, arm.pat.hir_id), OptionNone),
+ PatKind::TupleStruct(ref qpath, [first_pat], _) => {
+ is_res_lang_ctor(cx, cx.qpath_res(qpath, arm.pat.hir_id), ResultErr)
+ && matches!(first_pat.kind, PatKind::Wild)
+ },
+ PatKind::Wild => true,
+ _ => false,
}
}
impl<'tcx> LateLintPass<'tcx> for OptionIfLetElse {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
- if let Some(detection) = detect_option_if_let_else(cx, expr) {
+ // Don't lint macros and constants
+ if expr.span.from_expansion() || in_constant(cx, expr.hir_id) {
+ return;
+ }
+
+ let detection = detect_option_if_let_else(cx, expr).or_else(|| detect_option_match(cx, expr));
+ if let Some(det) = detection {
span_lint_and_sugg(
cx,
OPTION_IF_LET_ELSE,
expr.span,
- format!("use Option::{} instead of an if let/else", detection.method_sugg).as_str(),
+ format!("use Option::{} instead of an if let/else", det.method_sugg).as_str(),
"try",
format!(
"{}.{}({}, {})",
- detection.option, detection.method_sugg, detection.none_expr, detection.some_expr,
+ det.option, det.method_sugg, det.none_expr, det.some_expr
),
Applicability::MaybeIncorrect,
);
projects / rustc.git / blobdiff