// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution. // // Licensed under the Apache License, Version 2.0 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. use crate::utils::SpanlessEq; use crate::utils::{get_parent_expr, is_allowed, match_type, paths, span_lint, span_lint_and_sugg, walk_ptrs_ty}; use rustc::hir::*; use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; use rustc::{declare_tool_lint, lint_array}; use rustc_errors::Applicability; use syntax::source_map::Spanned; /// **What it does:** Checks for string appends of the form `x = x + y` (without /// `let`!). /// /// **Why is this bad?** It's not really bad, but some people think that the /// `.push_str(_)` method is more readable. /// /// **Known problems:** None. /// /// **Example:** /// /// ```rust /// let mut x = "Hello".to_owned(); /// x = x + ", World"; /// ``` declare_clippy_lint! { pub STRING_ADD_ASSIGN, pedantic, "using `x = x + ..` where x is a `String` instead of `push_str()`" } /// **What it does:** Checks for all instances of `x + _` where `x` is of type /// `String`, but only if [`string_add_assign`](#string_add_assign) does *not* /// match. /// /// **Why is this bad?** It's not bad in and of itself. However, this particular /// `Add` implementation is asymmetric (the other operand need not be `String`, /// but `x` does), while addition as mathematically defined is symmetric, also /// the `String::push_str(_)` function is a perfectly good replacement. /// Therefore some dislike it and wish not to have it in their code. /// /// That said, other people think that string addition, having a long tradition /// in other languages is actually fine, which is why we decided to make this /// particular lint `allow` by default. /// /// **Known problems:** None. /// /// **Example:** /// /// ```rust /// let x = "Hello".to_owned(); /// x + ", World" /// ``` declare_clippy_lint! { pub STRING_ADD, restriction, "using `x + ..` where x is a `String` instead of `push_str()`" } /// **What it does:** Checks for the `as_bytes` method called on string literals /// that contain only ASCII characters. /// /// **Why is this bad?** Byte string literals (e.g. `b"foo"`) can be used /// instead. They are shorter but less discoverable than `as_bytes()`. /// /// **Known Problems:** None. /// /// **Example:** /// ```rust /// let bs = "a byte string".as_bytes(); /// ``` declare_clippy_lint! { pub STRING_LIT_AS_BYTES, style, "calling `as_bytes` on a string literal instead of using a byte string literal" } #[derive(Copy, Clone)] pub struct StringAdd; impl LintPass for StringAdd { fn get_lints(&self) -> LintArray { lint_array!(STRING_ADD, STRING_ADD_ASSIGN) } } impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringAdd { fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) { if let ExprKind::Binary( Spanned { node: BinOpKind::Add, .. }, ref left, _, ) = e.node { if is_string(cx, left) { if !is_allowed(cx, STRING_ADD_ASSIGN, e.id) { let parent = get_parent_expr(cx, e); if let Some(p) = parent { if let ExprKind::Assign(ref target, _) = p.node { // avoid duplicate matches if SpanlessEq::new(cx).eq_expr(target, left) { return; } } } } span_lint( cx, STRING_ADD, e.span, "you added something to a string. Consider using `String::push_str()` instead", ); } } else if let ExprKind::Assign(ref target, ref src) = e.node { if is_string(cx, target) && is_add(cx, src, target) { span_lint( cx, STRING_ADD_ASSIGN, e.span, "you assigned the result of adding something to this string. Consider using \ `String::push_str()` instead", ); } } } } fn is_string(cx: &LateContext<'_, '_>, e: &Expr) -> bool { match_type(cx, walk_ptrs_ty(cx.tables.expr_ty(e)), &paths::STRING) } fn is_add(cx: &LateContext<'_, '_>, src: &Expr, target: &Expr) -> bool { match src.node { ExprKind::Binary( Spanned { node: BinOpKind::Add, .. }, ref left, _, ) => SpanlessEq::new(cx).eq_expr(target, left), ExprKind::Block(ref block, _) => { block.stmts.is_empty() && block.expr.as_ref().map_or(false, |expr| is_add(cx, expr, target)) }, _ => false, } } #[derive(Copy, Clone)] pub struct StringLitAsBytes; impl LintPass for StringLitAsBytes { fn get_lints(&self) -> LintArray { lint_array!(STRING_LIT_AS_BYTES) } } impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StringLitAsBytes { fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) { use crate::utils::{in_macro, snippet, snippet_with_applicability}; use syntax::ast::{LitKind, StrStyle}; if let ExprKind::MethodCall(ref path, _, ref args) = e.node { if path.ident.name == "as_bytes" { if let ExprKind::Lit(ref lit) = args[0].node { if let LitKind::Str(ref lit_content, style) = lit.node { let callsite = snippet(cx, args[0].span.source_callsite(), r#""foo""#); let expanded = if let StrStyle::Raw(n) = style { let term = (0..n).map(|_| '#').collect::(); format!("r{0}\"{1}\"{0}", term, lit_content.as_str()) } else { format!("\"{}\"", lit_content.as_str()) }; let mut applicability = Applicability::MachineApplicable; if callsite.starts_with("include_str!") { span_lint_and_sugg( cx, STRING_LIT_AS_BYTES, e.span, "calling `as_bytes()` on `include_str!(..)`", "consider using `include_bytes!(..)` instead", snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability).replacen( "include_str", "include_bytes", 1, ), applicability, ); } else if callsite == expanded && lit_content.as_str().chars().all(|c| c.is_ascii()) && !in_macro(args[0].span) { span_lint_and_sugg( cx, STRING_LIT_AS_BYTES, e.span, "calling `as_bytes()` on a string literal", "consider using a byte string literal instead", format!( "b{}", snippet_with_applicability(cx, args[0].span, r#""foo""#, &mut applicability) ), applicability, ); } } } } } } }