src/tools/clippy/clippy_lints/src/from_str_radix_10.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::sugg::Sugg;
   3 use clippy_utils::ty::is_type_diagnostic_item;
   4 use if_chain::if_chain;
   5 use rustc_errors::Applicability;
   6 use rustc_hir::{def, Expr, ExprKind, PrimTy, QPath, TyKind};
   7 use rustc_lint::{LateContext, LateLintPass};
   8 use rustc_middle::ty::Ty;
   9 use rustc_session::{declare_lint_pass, declare_tool_lint};
  10 use rustc_span::symbol::sym;
  11
  12 declare_clippy_lint! {
  13     /// **What it does:**
  14     /// Checks for function invocations of the form `primitive::from_str_radix(s, 10)`
  15     ///
  16     /// **Why is this bad?**
  17     /// This specific common use case can be rewritten as `s.parse::<primitive>()`
  18     /// (and in most cases, the turbofish can be removed), which reduces code length
  19     /// and complexity.
  20     ///
  21     /// **Known problems:**
  22     /// This lint may suggest using (&<expression>).parse() instead of <expression>.parse() directly
  23     /// in some cases, which is correct but adds unnecessary complexity to the code.
  24     ///
  25     /// **Example:**
  26     ///
  27     /// ```ignore
  28     /// let input: &str = get_input();
  29     /// let num = u16::from_str_radix(input, 10)?;
  30     /// ```
  31     /// Use instead:
  32     /// ```ignore
  33     /// let input: &str = get_input();
  34     /// let num: u16 = input.parse()?;
  35     /// ```
  36     pub FROM_STR_RADIX_10,
  37     style,
  38     "from_str_radix with radix 10"
  39 }
  40
  41 declare_lint_pass!(FromStrRadix10 => [FROM_STR_RADIX_10]);
  42
  43 impl LateLintPass<'tcx> for FromStrRadix10 {
  44     fn check_expr(&mut self, cx: &LateContext<'tcx>, exp: &Expr<'tcx>) {
  45         if_chain! {
  46             if let ExprKind::Call(maybe_path, arguments) = &exp.kind;
  47             if let ExprKind::Path(QPath::TypeRelative(ty, pathseg)) = &maybe_path.kind;
  48
  49             // check if the first part of the path is some integer primitive
  50             if let TyKind::Path(ty_qpath) = &ty.kind;
  51             let ty_res = cx.qpath_res(ty_qpath, ty.hir_id);
  52             if let def::Res::PrimTy(prim_ty) = ty_res;
  53             if matches!(prim_ty, PrimTy::Int(_) | PrimTy::Uint(_));
  54
  55             // check if the second part of the path indeed calls the associated
  56             // function `from_str_radix`
  57             if pathseg.ident.name.as_str() == "from_str_radix";
  58
  59             // check if the second argument is a primitive `10`
  60             if arguments.len() == 2;
  61             if let ExprKind::Lit(lit) = &arguments[1].kind;
  62             if let rustc_ast::ast::LitKind::Int(10, _) = lit.node;
  63
  64             then {
  65                 let expr = if let ExprKind::AddrOf(_, _, expr) = &arguments[0].kind {
  66                     let ty = cx.typeck_results().expr_ty(expr);
  67                     if is_ty_stringish(cx, ty) {
  68                         expr
  69                     } else {
  70                         &arguments[0]
  71                     }
  72                 } else {
  73                     &arguments[0]
  74                 };
  75
  76                 let sugg = Sugg::hir_with_applicability(
  77                     cx,
  78                     expr,
  79                     "<string>",
  80                     &mut Applicability::MachineApplicable
  81                 ).maybe_par();
  82
  83                 span_lint_and_sugg(
  84                     cx,
  85                     FROM_STR_RADIX_10,
  86                     exp.span,
  87                     "this call to `from_str_radix` can be replaced with a call to `str::parse`",
  88                     "try",
  89                     format!("{}.parse::<{}>()", sugg, prim_ty.name_str()),
  90                     Applicability::MaybeIncorrect
  91                 );
  92             }
  93         }
  94     }
  95 }
  96
  97 /// Checks if a Ty is `String` or `&str`
  98 fn is_ty_stringish(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
  99     is_type_diagnostic_item(cx, ty, sym::string_type) || is_type_diagnostic_item(cx, ty, sym::str)
 100 }