use rustc::lint::*; use rustc::hir; use utils::{is_try, match_qpath, match_trait_method, paths, span_lint}; /// **What it does:** Checks for unused written/read amount. /// /// **Why is this bad?** `io::Write::write` and `io::Read::read` are not /// guaranteed to /// process the entire buffer. They return how many bytes were processed, which /// might be smaller /// than a given buffer's length. If you don't need to deal with /// partial-write/read, use /// `write_all`/`read_exact` instead. /// /// **Known problems:** Detects only common patterns. /// /// **Example:** /// ```rust,ignore /// use std::io; /// fn foo(w: &mut W) -> io::Result<()> { /// // must be `w.write_all(b"foo")?;` /// w.write(b"foo")?; /// Ok(()) /// } /// ``` declare_clippy_lint! { pub UNUSED_IO_AMOUNT, correctness, "unused written/read amount" } pub struct UnusedIoAmount; impl LintPass for UnusedIoAmount { fn get_lints(&self) -> LintArray { lint_array!(UNUSED_IO_AMOUNT) } } impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedIoAmount { fn check_stmt(&mut self, cx: &LateContext, s: &hir::Stmt) { let expr = match s.node { hir::StmtSemi(ref expr, _) | hir::StmtExpr(ref expr, _) => &**expr, _ => return, }; match expr.node { hir::ExprMatch(ref res, _, _) if is_try(expr).is_some() => { if let hir::ExprCall(ref func, ref args) = res.node { if let hir::ExprPath(ref path) = func.node { if match_qpath(path, &paths::TRY_INTO_RESULT) && args.len() == 1 { check_method_call(cx, &args[0], expr); } } } else { check_method_call(cx, res, expr); } }, hir::ExprMethodCall(ref path, _, ref args) => match &*path.name.as_str() { "expect" | "unwrap" | "unwrap_or" | "unwrap_or_else" => { check_method_call(cx, &args[0], expr); }, _ => (), }, _ => (), } } } fn check_method_call(cx: &LateContext, call: &hir::Expr, expr: &hir::Expr) { if let hir::ExprMethodCall(ref path, _, _) = call.node { let symbol = &*path.name.as_str(); if match_trait_method(cx, call, &paths::IO_READ) && symbol == "read" { span_lint( cx, UNUSED_IO_AMOUNT, expr.span, "handle read amount returned or use `Read::read_exact` instead", ); } else if match_trait_method(cx, call, &paths::IO_WRITE) && symbol == "write" { span_lint( cx, UNUSED_IO_AMOUNT, expr.span, "handle written amount returned or use `Write::write_all` instead", ); } } }