use rustc::lint::*; use std::collections::HashMap; use std::char; use syntax::ast::*; use syntax::codemap::Span; use syntax::visit::FnKind; use utils::{span_lint, span_help_and_lint, snippet, snippet_opt, span_lint_and_then}; /// **What it does:** 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:** /// ```rust /// let { a: _, b: ref b, c: _ } = .. /// ``` declare_lint! { pub UNNEEDED_FIELD_PATTERN, Warn, "struct fields bound to a wildcard instead of using `..`" } /// **What it does:** Checks for function arguments having the similar names /// differing by an underscore. /// /// **Why is this bad?** It affects code readability. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// 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:** 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 /// (|| 42)() /// ``` declare_lint! { pub REDUNDANT_CLOSURE_CALL, Warn, "throwaway closures called in the expression they are defined" } /// **What it does:** 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:** /// ```rust /// --x; /// ``` declare_lint! { pub DOUBLE_NEG, Warn, "`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++" } /// **What it does:** Warns on hexadecimal literals with mixed-case letter digits. /// /// **Why is this bad?** It looks confusing. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// let y = 0x1a9BAcD; /// ``` declare_lint! { pub MIXED_CASE_HEX_LITERALS, Warn, "hex literals whose letter digits are not consistently upper- or lowercased" } /// **What it does:** Warns if literal suffixes are not separated by an underscore. /// /// **Why is this bad?** It is much less readable. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// let y = 123832i32; /// ``` declare_lint! { pub UNSEPARATED_LITERAL_SUFFIX, Allow, "literals whose suffix is not separated by an underscore" } /// **What it does:** Warns if an integral constant literal starts with `0`. /// /// **Why is this bad?** In some languages (including the infamous C language and most of its /// familly), this marks an octal constant. In Rust however, this is a decimal constant. This could /// be confusing for both the writer and a reader of the constant. /// /// **Known problems:** None. /// /// **Example:** /// /// In Rust: /// ```rust /// fn main() { /// let a = 0123; /// println!("{}", a); /// } /// ``` /// /// prints `123`, while in C: /// /// ```c /// #include /// /// int main() { /// int a = 0123; /// printf("%d\n", a); /// } /// ``` /// /// prints `83` (as `83 == 0o123` while `123 == 0o173`). declare_lint! { pub ZERO_PREFIXED_LITERAL, Warn, "integer literals starting with `0`" } #[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, MIXED_CASE_HEX_LITERALS, UNSEPARATED_LITERAL_SUFFIX, ZERO_PREFIXED_LITERAL) } } 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 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"); } } ExprKind::Lit(ref lit) => { if_let_chain! {[ let LitKind::Int(value, ..) = lit.node, let Some(src) = snippet_opt(cx, lit.span), let Some(firstch) = src.chars().next(), char::to_digit(firstch, 10).is_some() ], { let mut prev = '\0'; for ch in src.chars() { if ch == 'i' || ch == 'u' { if prev != '_' { span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span, "integer type suffix should be separated by an underscore"); } break; } prev = ch; } if src.starts_with("0x") { let mut seen = (false, false); for ch in src.chars() { match ch { 'a' ... 'f' => seen.0 = true, 'A' ... 'F' => seen.1 = true, 'i' | 'u' => break, // start of suffix already _ => () } } if seen.0 && seen.1 { span_lint(cx, MIXED_CASE_HEX_LITERALS, lit.span, "inconsistent casing in hexadecimal literal"); } } else if src.starts_with("0b") || src.starts_with("0o") { /* nothing to do */ } else if value != 0 && src.starts_with('0') { span_lint_and_then(cx, ZERO_PREFIXED_LITERAL, lit.span, "this is a decimal constant", |db| { db.span_suggestion(lit.span, "if you mean to use a decimal constant, remove the `0` to remove confusion:", src[1..].to_string()); db.span_suggestion(lit.span, "if you mean to use an octal constant, use `0o`:", format!("0o{}", &src[1..])); }); } }} if_let_chain! {[ let LitKind::Float(..) = lit.node, let Some(src) = snippet_opt(cx, lit.span), let Some(firstch) = src.chars().next(), char::to_digit(firstch, 10).is_some() ], { let mut prev = '\0'; for ch in src.chars() { if ch == 'f' { if prev != '_' { span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span, "float type suffix should be separated by an underscore"); } break; } prev = ch; } }} } _ => () } } 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"); } }} } } }