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