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Auto merge of #5800 - montrivo:bugfix/redundant_closure, r=matthiaskrgr
redundant_closure_call - don't lint when used more than once Fixes #3354. changelog: fix redundant_closure_call false positive when closure called more than once
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,151 @@ | ||
| use crate::utils::{snippet_with_applicability, span_lint, span_lint_and_then}; | ||
| use if_chain::if_chain; | ||
| use rustc_ast::ast; | ||
| use rustc_ast::visit as ast_visit; | ||
| use rustc_ast::visit::Visitor as AstVisitor; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir as hir; | ||
| use rustc_hir::intravisit as hir_visit; | ||
| use rustc_hir::intravisit::Visitor as HirVisitor; | ||
| use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext}; | ||
| use rustc_middle::hir::map::Map; | ||
| use rustc_middle::lint::in_external_macro; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// **What it does:** Detects closures called in the same expression where they | ||
| /// are defined. | ||
| /// | ||
| /// **Why is this bad?** It is unnecessarily adding to the expression's | ||
| /// complexity. | ||
| /// | ||
| /// **Known problems:** None. | ||
| /// | ||
| /// **Example:** | ||
| /// ```rust,ignore | ||
| /// // Bad | ||
| /// let a = (|| 42)() | ||
| /// | ||
| /// // Good | ||
| /// let a = 42 | ||
| /// ``` | ||
| pub REDUNDANT_CLOSURE_CALL, | ||
| complexity, | ||
| "throwaway closures called in the expression they are defined" | ||
| } | ||
|
|
||
| declare_lint_pass!(RedundantClosureCall => [REDUNDANT_CLOSURE_CALL]); | ||
|
|
||
| // Used to find `return` statements or equivalents e.g., `?` | ||
| struct ReturnVisitor { | ||
| found_return: bool, | ||
| } | ||
|
|
||
| impl ReturnVisitor { | ||
| #[must_use] | ||
| fn new() -> Self { | ||
| Self { found_return: false } | ||
| } | ||
| } | ||
|
|
||
| impl<'ast> ast_visit::Visitor<'ast> for ReturnVisitor { | ||
| fn visit_expr(&mut self, ex: &'ast ast::Expr) { | ||
| if let ast::ExprKind::Ret(_) = ex.kind { | ||
| self.found_return = true; | ||
| } else if let ast::ExprKind::Try(_) = ex.kind { | ||
| self.found_return = true; | ||
| } | ||
|
|
||
| ast_visit::walk_expr(self, ex) | ||
| } | ||
| } | ||
|
|
||
| impl EarlyLintPass for RedundantClosureCall { | ||
| fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) { | ||
| if in_external_macro(cx.sess(), expr.span) { | ||
| return; | ||
| } | ||
| if_chain! { | ||
| if let ast::ExprKind::Call(ref paren, _) = expr.kind; | ||
| if let ast::ExprKind::Paren(ref closure) = paren.kind; | ||
| if let ast::ExprKind::Closure(_, _, _, ref decl, ref block, _) = closure.kind; | ||
| then { | ||
| let mut visitor = ReturnVisitor::new(); | ||
| visitor.visit_expr(block); | ||
| if !visitor.found_return { | ||
| span_lint_and_then( | ||
| cx, | ||
| REDUNDANT_CLOSURE_CALL, | ||
| expr.span, | ||
| "try not to call a closure in the expression where it is declared.", | ||
| |diag| { | ||
| if decl.inputs.is_empty() { | ||
| let mut app = Applicability::MachineApplicable; | ||
| let hint = | ||
| snippet_with_applicability(cx, block.span, "..", &mut app).into_owned(); | ||
| diag.span_suggestion(expr.span, "try doing something like", hint, app); | ||
| } | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for RedundantClosureCall { | ||
| fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx hir::Block<'_>) { | ||
| fn count_closure_usage<'tcx>(block: &'tcx hir::Block<'_>, path: &'tcx hir::Path<'tcx>) -> usize { | ||
| struct ClosureUsageCount<'tcx> { | ||
| path: &'tcx hir::Path<'tcx>, | ||
| count: usize, | ||
| }; | ||
| impl<'tcx> hir_visit::Visitor<'tcx> for ClosureUsageCount<'tcx> { | ||
| type Map = Map<'tcx>; | ||
|
|
||
| fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) { | ||
| if_chain! { | ||
| if let hir::ExprKind::Call(ref closure, _) = expr.kind; | ||
| if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = closure.kind; | ||
| if self.path.segments[0].ident == path.segments[0].ident | ||
| && self.path.res == path.res; | ||
| then { | ||
| self.count += 1; | ||
| } | ||
| } | ||
| hir_visit::walk_expr(self, expr); | ||
| } | ||
|
|
||
| fn nested_visit_map(&mut self) -> hir_visit::NestedVisitorMap<Self::Map> { | ||
| hir_visit::NestedVisitorMap::None | ||
| } | ||
| }; | ||
| let mut closure_usage_count = ClosureUsageCount { path, count: 0 }; | ||
| closure_usage_count.visit_block(block); | ||
| closure_usage_count.count | ||
| } | ||
|
|
||
| for w in block.stmts.windows(2) { | ||
| if_chain! { | ||
| if let hir::StmtKind::Local(ref local) = w[0].kind; | ||
| if let Option::Some(ref t) = local.init; | ||
| if let hir::ExprKind::Closure(..) = t.kind; | ||
| if let hir::PatKind::Binding(_, _, ident, _) = local.pat.kind; | ||
| if let hir::StmtKind::Semi(ref second) = w[1].kind; | ||
| if let hir::ExprKind::Assign(_, ref call, _) = second.kind; | ||
| if let hir::ExprKind::Call(ref closure, _) = call.kind; | ||
| if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = closure.kind; | ||
| if ident == path.segments[0].ident; | ||
| if count_closure_usage(block, path) == 1; | ||
| then { | ||
| span_lint( | ||
| cx, | ||
| REDUNDANT_CLOSURE_CALL, | ||
| second.span, | ||
| "closure called just once immediately after it was declared", | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
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