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}; /// **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" } #[derive(Copy, Clone)] pub struct MiscEarly; impl LintPass for MiscEarly { fn get_lints(&self) -> LintArray { lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT) } } impl EarlyLintPass for MiscEarly { fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) { if let PatStruct(ref npat, ref pfields, _) = pat.node { let mut wilds = 0; let type_name = match npat.segments.last() { Some(elem) => format!("{}", elem.identifier.name), None => String::new(), }; for field in pfields { if field.node.pat.node == PatWild { 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 != PatWild { if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) { normal.push(n); } } } for field in pfields { if field.node.pat.node == PatWild { 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 PatIdent(_, sp_ident, None) = arg.pat.node { let arg_name = sp_ident.node.to_string(); if arg_name.starts_with("_") { if let Some(correspondance) = registered_names.get(&arg_name[1..]) { span_lint(cx, DUPLICATE_UNDERSCORE_ARGUMENT, *correspondance, &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); } } } } }