diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/matches/manual_filter.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/matches/manual_filter.rs | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/matches/manual_filter.rs b/src/tools/clippy/clippy_lints/src/matches/manual_filter.rs new file mode 100644 index 000000000..66ba1f6f9 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/matches/manual_filter.rs @@ -0,0 +1,153 @@ +use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::ty::is_type_diagnostic_item; +use clippy_utils::visitors::contains_unsafe_block; +use clippy_utils::{is_res_lang_ctor, path_res, path_to_local_id}; + +use rustc_hir::LangItem::OptionSome; +use rustc_hir::{Arm, Expr, ExprKind, HirId, Pat, PatKind}; +use rustc_lint::LateContext; +use rustc_span::{sym, SyntaxContext}; + +use super::manual_utils::{check_with, SomeExpr}; +use super::MANUAL_FILTER; + +// Function called on the <expr> of `[&+]Some((ref | ref mut) x) => <expr>` +// Need to check if it's of the form `<expr>=if <cond> {<then_expr>} else {<else_expr>}` +// AND that only one `then/else_expr` resolves to `Some(x)` while the other resolves to `None` +// return the `cond` expression if so. +fn get_cond_expr<'tcx>( + cx: &LateContext<'tcx>, + pat: &Pat<'_>, + expr: &'tcx Expr<'_>, + ctxt: SyntaxContext, +) -> Option<SomeExpr<'tcx>> { + if_chain! { + if let Some(block_expr) = peels_blocks_incl_unsafe_opt(expr); + if let ExprKind::If(cond, then_expr, Some(else_expr)) = block_expr.kind; + if let PatKind::Binding(_,target, ..) = pat.kind; + if let (then_visitor, else_visitor) + = (is_some_expr(cx, target, ctxt, then_expr), + is_some_expr(cx, target, ctxt, else_expr)); + if then_visitor != else_visitor; // check that one expr resolves to `Some(x)`, the other to `None` + then { + return Some(SomeExpr { + expr: peels_blocks_incl_unsafe(cond.peel_drop_temps()), + needs_unsafe_block: contains_unsafe_block(cx, expr), + needs_negated: !then_visitor // if the `then_expr` resolves to `None`, need to negate the cond + }) + } + }; + None +} + +fn peels_blocks_incl_unsafe_opt<'a>(expr: &'a Expr<'a>) -> Option<&'a Expr<'a>> { + // we don't want to use `peel_blocks` here because we don't care if the block is unsafe, it's + // checked by `contains_unsafe_block` + if let ExprKind::Block(block, None) = expr.kind { + if block.stmts.is_empty() { + return block.expr; + } + }; + None +} + +fn peels_blocks_incl_unsafe<'a>(expr: &'a Expr<'a>) -> &'a Expr<'a> { + peels_blocks_incl_unsafe_opt(expr).unwrap_or(expr) +} + +// function called for each <expr> expression: +// Some(x) => if <cond> { +// <expr> +// } else { +// <expr> +// } +// Returns true if <expr> resolves to `Some(x)`, `false` otherwise +fn is_some_expr<'tcx>(cx: &LateContext<'_>, target: HirId, ctxt: SyntaxContext, expr: &'tcx Expr<'_>) -> bool { + if let Some(inner_expr) = peels_blocks_incl_unsafe_opt(expr) { + // there can be not statements in the block as they would be removed when switching to `.filter` + if let ExprKind::Call(callee, [arg]) = inner_expr.kind { + return ctxt == expr.span.ctxt() + && is_res_lang_ctor(cx, path_res(cx, callee), OptionSome) + && path_to_local_id(arg, target); + } + }; + false +} + +// given the closure: `|<pattern>| <expr>` +// returns `|&<pattern>| <expr>` +fn add_ampersand_if_copy(body_str: String, has_copy_trait: bool) -> String { + if has_copy_trait { + let mut with_ampersand = body_str; + with_ampersand.insert(1, '&'); + with_ampersand + } else { + body_str + } +} + +pub(super) fn check_match<'tcx>( + cx: &LateContext<'tcx>, + scrutinee: &'tcx Expr<'_>, + arms: &'tcx [Arm<'_>], + expr: &'tcx Expr<'_>, +) { + let ty = cx.typeck_results().expr_ty(expr); + if is_type_diagnostic_item(cx, ty, sym::Option) + && let [first_arm, second_arm] = arms + && first_arm.guard.is_none() + && second_arm.guard.is_none() + { + check(cx, expr, scrutinee, first_arm.pat, first_arm.body, Some(second_arm.pat), second_arm.body); + } +} + +pub(super) fn check_if_let<'tcx>( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + let_pat: &'tcx Pat<'_>, + let_expr: &'tcx Expr<'_>, + then_expr: &'tcx Expr<'_>, + else_expr: &'tcx Expr<'_>, +) { + check(cx, expr, let_expr, let_pat, then_expr, None, else_expr); +} + +fn check<'tcx>( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + scrutinee: &'tcx Expr<'_>, + then_pat: &'tcx Pat<'_>, + then_body: &'tcx Expr<'_>, + else_pat: Option<&'tcx Pat<'_>>, + else_body: &'tcx Expr<'_>, +) { + if let Some(sugg_info) = check_with( + cx, + expr, + scrutinee, + then_pat, + then_body, + else_pat, + else_body, + get_cond_expr, + ) { + let body_str = add_ampersand_if_copy(sugg_info.body_str, sugg_info.scrutinee_impl_copy); + span_lint_and_sugg( + cx, + MANUAL_FILTER, + expr.span, + "manual implementation of `Option::filter`", + "try this", + if sugg_info.needs_brackets { + format!( + "{{ {}{}.filter({body_str}) }}", + sugg_info.scrutinee_str, sugg_info.as_ref_str + ) + } else { + format!("{}{}.filter({body_str})", sugg_info.scrutinee_str, sugg_info.as_ref_str) + }, + sugg_info.app, + ); + } +} |