89 lines
3.0 KiB
Rust
89 lines
3.0 KiB
Rust
use rustc::lint::*;
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use rustc::ty::{self, Ty};
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use rustc::ty::subst::Subst;
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use rustc::hir::*;
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use utils::span_lint;
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/// **What it does:** Detects giving a mutable reference to a function that only
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/// requires an immutable reference.
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///
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/// **Why is this bad?** The immutable reference rules out all other references
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/// to the value. Also the code misleads about the intent of the call site.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// my_vec.push(&mut value)
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/// ```
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declare_lint! {
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pub UNNECESSARY_MUT_PASSED,
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Warn,
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"an argument passed as a mutable reference although the callee only demands an \
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immutable reference"
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}
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#[derive(Copy, Clone)]
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pub struct UnnecessaryMutPassed;
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impl LintPass for UnnecessaryMutPassed {
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fn get_lints(&self) -> LintArray {
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lint_array!(UNNECESSARY_MUT_PASSED)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnecessaryMutPassed {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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match e.node {
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ExprCall(ref fn_expr, ref arguments) => if let ExprPath(ref path) = fn_expr.node {
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check_arguments(
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cx,
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arguments,
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cx.tables.expr_ty(fn_expr),
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&print::to_string(print::NO_ANN, |s| s.print_qpath(path, false)),
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);
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},
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ExprMethodCall(ref path, _, ref arguments) => {
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let def_id = cx.tables.type_dependent_defs()[e.hir_id].def_id();
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let substs = cx.tables.node_substs(e.hir_id);
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let method_type = cx.tcx.type_of(def_id).subst(cx.tcx, substs);
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check_arguments(cx, arguments, method_type, &path.name.as_str())
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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_arguments<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, arguments: &[Expr], type_definition: Ty<'tcx>, name: &str) {
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match type_definition.sty {
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ty::TyFnDef(..) | ty::TyFnPtr(_) => {
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let parameters = type_definition.fn_sig(cx.tcx).skip_binder().inputs();
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for (argument, parameter) in arguments.iter().zip(parameters.iter()) {
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match parameter.sty {
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ty::TyRef(
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_,
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ty::TypeAndMut {
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mutbl: MutImmutable,
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..
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},
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) |
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ty::TyRawPtr(ty::TypeAndMut {
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mutbl: MutImmutable,
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..
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}) => if let ExprAddrOf(MutMutable, _) = argument.node {
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span_lint(
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cx,
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UNNECESSARY_MUT_PASSED,
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argument.span,
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&format!("The function/method `{}` doesn't need a mutable reference", name),
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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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}
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}
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