use rustc::lint::*; use std::collections::HashMap; use syntax::ast::*; use syntax::codemap::Span; use syntax::visit::FnKind; use utils::{span_lint, span_help_and_lint, snippet, span_lint_and_then}; /// **What it does:** This lint checks for structure field patterns bound to wildcards. /// /// **Why is this bad?** Using `..` instead is shorter and leaves the focus on the fields that are actually bound. /// /// **Known problems:** None. /// /// **Example:** `let { a: _, b: ref b, c: _ } = ..` declare_lint! { pub UNNEEDED_FIELD_PATTERN, Warn, "Struct fields are bound to a wildcard instead of using `..`" } /// **What it does:** This lint checks for function arguments having the similar names differing by an underscore /// /// **Why is this bad?** It affects code readability /// /// **Known problems:** None. /// /// **Example:** `fn foo(a: i32, _a: i32) {}` declare_lint! { pub DUPLICATE_UNDERSCORE_ARGUMENT, Warn, "Function arguments having names which only differ by an underscore" } /// **What it does:** This lint 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:** `(|| 42)()` declare_lint! { pub REDUNDANT_CLOSURE_CALL, Warn, "Closures should not be called in the expression they are defined" } /// **What it does:** This lint detects expressions of the form `--x` /// /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was decremented. /// /// **Known problems:** None. /// /// **Example:** `--x;` declare_lint! { pub DOUBLE_NEG, Warn, "`--x` is a double negation of `x` and not a pre-decrement as in C or C++" } #[derive(Copy, Clone)] pub struct MiscEarly; impl LintPass for MiscEarly { fn get_lints(&self) -> LintArray { lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT, REDUNDANT_CLOSURE_CALL, DOUBLE_NEG) } } impl EarlyLintPass for MiscEarly { fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) { if let PatKind::Struct(ref npat, ref pfields, _) = pat.node { let mut wilds = 0; let type_name = npat.segments.last().expect("A path must have at least one segment").identifier.name; for field in pfields { if field.node.pat.node == PatKind::Wild { wilds += 1; } } if !pfields.is_empty() && wilds == pfields.len() { span_help_and_lint(cx, UNNEEDED_FIELD_PATTERN, pat.span, "All the struct fields are matched to a wildcard pattern, consider using `..`.", &format!("Try with `{} {{ .. }}` instead", type_name)); return; } if wilds > 0 { let mut normal = vec![]; for field in pfields { if field.node.pat.node != PatKind::Wild { if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) { normal.push(n); } } } for field in pfields { if field.node.pat.node == PatKind::Wild { wilds -= 1; if wilds > 0 { span_lint(cx, UNNEEDED_FIELD_PATTERN, field.span, "You matched a field with a wildcard pattern. Consider using `..` instead"); } else { span_help_and_lint(cx, UNNEEDED_FIELD_PATTERN, field.span, "You matched a field with a wildcard pattern. Consider using `..` \ instead", &format!("Try with `{} {{ {}, .. }}`", type_name, normal[..].join(", "))); } } } } } } fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) { let mut registered_names: HashMap = HashMap::new(); for ref arg in &decl.inputs { if let PatKind::Ident(_, sp_ident, None) = arg.pat.node { let arg_name = sp_ident.node.to_string(); if arg_name.starts_with('_') { if let Some(correspondence) = registered_names.get(&arg_name[1..]) { span_lint(cx, DUPLICATE_UNDERSCORE_ARGUMENT, *correspondence, &format!("`{}` already exists, having another argument having almost the same \ name makes code comprehension and documentation more difficult", arg_name[1..].to_owned()));; } } else { registered_names.insert(arg_name, arg.pat.span); } } } } fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) { match expr.node { ExprKind::Call(ref paren, _) => { if let ExprKind::Paren(ref closure) = paren.node { if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node { span_lint_and_then(cx, REDUNDANT_CLOSURE_CALL, expr.span, "Try not to call a closure in the expression where it is declared.", |db| { if decl.inputs.is_empty() { let hint = snippet(cx, block.span, "..").into_owned(); db.span_suggestion(expr.span, "Try doing something like: ", hint); } }); } } } ExprKind::Unary(UnOp::Neg, ref inner) => { if let ExprKind::Unary(UnOp::Neg, _) = inner.node { span_lint(cx, DOUBLE_NEG, expr.span, "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op"); } } _ => () } } fn check_block(&mut self, cx: &EarlyContext, block: &Block) { for w in block.stmts.windows(2) { if_let_chain! {[ let StmtKind::Local(ref local) = w[0].node, let Option::Some(ref t) = local.init, let ExprKind::Closure(_, _, _, _) = t.node, let PatKind::Ident(_, sp_ident, _) = local.pat.node, let StmtKind::Semi(ref second) = w[1].node, let ExprKind::Assign(_, ref call) = second.node, let ExprKind::Call(ref closure, _) = call.node, let ExprKind::Path(_, ref path) = closure.node ], { if sp_ident.node == (&path.segments[0]).identifier { span_lint(cx, REDUNDANT_CLOSURE_CALL, second.span, "Closure called just once immediately after it was declared"); } }} } } }