src/tools/clippy/clippy_lints/src/methods/str_splitn.rs

   1 use clippy_utils::consts::{constant, Constant};
   2 use clippy_utils::diagnostics::span_lint_and_sugg;
   3 use clippy_utils::source::snippet_with_context;
   4 use clippy_utils::{is_diag_item_method, match_def_path, paths};
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::{Expr, ExprKind, HirId, LangItem, Node, QPath};
   8 use rustc_lint::LateContext;
   9 use rustc_middle::ty::{self, adjustment::Adjust};
  10 use rustc_span::{symbol::sym, Span, SyntaxContext};
  11
  12 use super::MANUAL_SPLIT_ONCE;
  13
  14 pub(super) fn check_manual_split_once(
  15     cx: &LateContext<'_>,
  16     method_name: &str,
  17     expr: &Expr<'_>,
  18     self_arg: &Expr<'_>,
  19     pat_arg: &Expr<'_>,
  20 ) {
  21     if !cx.typeck_results().expr_ty_adjusted(self_arg).peel_refs().is_str() {
  22         return;
  23     }
  24
  25     let ctxt = expr.span.ctxt();
  26     let (method_name, msg, reverse) = if method_name == "splitn" {
  27         ("split_once", "manual implementation of `split_once`", false)
  28     } else {
  29         ("rsplit_once", "manual implementation of `rsplit_once`", true)
  30     };
  31     let usage = match parse_iter_usage(cx, ctxt, cx.tcx.hir().parent_iter(expr.hir_id), reverse) {
  32         Some(x) => x,
  33         None => return,
  34     };
  35
  36     let mut app = Applicability::MachineApplicable;
  37     let self_snip = snippet_with_context(cx, self_arg.span, ctxt, "..", &mut app).0;
  38     let pat_snip = snippet_with_context(cx, pat_arg.span, ctxt, "..", &mut app).0;
  39
  40     let sugg = match usage.kind {
  41         IterUsageKind::NextTuple => {
  42             format!("{}.{}({})", self_snip, method_name, pat_snip)
  43         },
  44         IterUsageKind::RNextTuple => format!("{}.{}({}).map(|(x, y)| (y, x))", self_snip, method_name, pat_snip),
  45         IterUsageKind::Next | IterUsageKind::Second => {
  46             let self_deref = {
  47                 let adjust = cx.typeck_results().expr_adjustments(self_arg);
  48                 if adjust.is_empty() {
  49                     String::new()
  50                 } else if cx.typeck_results().expr_ty(self_arg).is_box()
  51                     || adjust
  52                         .iter()
  53                         .any(|a| matches!(a.kind, Adjust::Deref(Some(_))) || a.target.is_box())
  54                 {
  55                     format!("&{}", "*".repeat(adjust.len() - 1))
  56                 } else {
  57                     "*".repeat(adjust.len() - 2)
  58                 }
  59             };
  60             if matches!(usage.kind, IterUsageKind::Next) {
  61                 match usage.unwrap_kind {
  62                     Some(UnwrapKind::Unwrap) => {
  63                         if reverse {
  64                             format!("{}.{}({}).unwrap().0", self_snip, method_name, pat_snip)
  65                         } else {
  66                             format!(
  67                                 "{}.{}({}).map_or({}{}, |x| x.0)",
  68                                 self_snip, method_name, pat_snip, self_deref, &self_snip
  69                             )
  70                         }
  71                     },
  72                     Some(UnwrapKind::QuestionMark) => {
  73                         format!(
  74                             "{}.{}({}).map_or({}{}, |x| x.0)",
  75                             self_snip, method_name, pat_snip, self_deref, &self_snip
  76                         )
  77                     },
  78                     None => {
  79                         format!(
  80                             "Some({}.{}({}).map_or({}{}, |x| x.0))",
  81                             &self_snip, method_name, pat_snip, self_deref, &self_snip
  82                         )
  83                     },
  84                 }
  85             } else {
  86                 match usage.unwrap_kind {
  87                     Some(UnwrapKind::Unwrap) => {
  88                         if reverse {
  89                             // In this case, no better suggestion is offered.
  90                             return;
  91                         }
  92                         format!("{}.{}({}).unwrap().1", self_snip, method_name, pat_snip)
  93                     },
  94                     Some(UnwrapKind::QuestionMark) => {
  95                         format!("{}.{}({})?.1", self_snip, method_name, pat_snip)
  96                     },
  97                     None => {
  98                         format!("{}.{}({}).map(|x| x.1)", self_snip, method_name, pat_snip)
  99                     },
 100                 }
 101             }
 102         },
 103     };
 104
 105     span_lint_and_sugg(cx, MANUAL_SPLIT_ONCE, usage.span, msg, "try this", sugg, app);
 106 }
 107
 108 enum IterUsageKind {
 109     Next,
 110     Second,
 111     NextTuple,
 112     RNextTuple,
 113 }
 114
 115 enum UnwrapKind {
 116     Unwrap,
 117     QuestionMark,
 118 }
 119
 120 struct IterUsage {
 121     kind: IterUsageKind,
 122     unwrap_kind: Option<UnwrapKind>,
 123     span: Span,
 124 }
 125
 126 #[allow(clippy::too_many_lines)]
 127 fn parse_iter_usage<'tcx>(
 128     cx: &LateContext<'tcx>,
 129     ctxt: SyntaxContext,
 130     mut iter: impl Iterator<Item = (HirId, Node<'tcx>)>,
 131     reverse: bool,
 132 ) -> Option<IterUsage> {
 133     let (kind, span) = match iter.next() {
 134         Some((_, Node::Expr(e))) if e.span.ctxt() == ctxt => {
 135             let (name, args) = if let ExprKind::MethodCall(name, [_, args @ ..], _) = e.kind {
 136                 (name, args)
 137             } else {
 138                 return None;
 139             };
 140             let did = cx.typeck_results().type_dependent_def_id(e.hir_id)?;
 141             let iter_id = cx.tcx.get_diagnostic_item(sym::Iterator)?;
 142
 143             match (name.ident.as_str(), args) {
 144                 ("next", []) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
 145                     if reverse {
 146                         (IterUsageKind::Second, e.span)
 147                     } else {
 148                         (IterUsageKind::Next, e.span)
 149                     }
 150                 },
 151                 ("next_tuple", []) => {
 152                     return if_chain! {
 153                         if match_def_path(cx, did, &paths::ITERTOOLS_NEXT_TUPLE);
 154                         if let ty::Adt(adt_def, subs) = cx.typeck_results().expr_ty(e).kind();
 155                         if cx.tcx.is_diagnostic_item(sym::Option, adt_def.did);
 156                         if let ty::Tuple(subs) = subs.type_at(0).kind();
 157                         if subs.len() == 2;
 158                         then {
 159                             Some(IterUsage {
 160                                 kind: if reverse { IterUsageKind::RNextTuple } else { IterUsageKind::NextTuple },
 161                                 span: e.span,
 162                                 unwrap_kind: None
 163                             })
 164                         } else {
 165                             None
 166                         }
 167                     };
 168                 },
 169                 ("nth" | "skip", [idx_expr]) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
 170                     if let Some((Constant::Int(idx), _)) = constant(cx, cx.typeck_results(), idx_expr) {
 171                         let span = if name.ident.as_str() == "nth" {
 172                             e.span
 173                         } else {
 174                             if_chain! {
 175                                 if let Some((_, Node::Expr(next_expr))) = iter.next();
 176                                 if let ExprKind::MethodCall(next_name, [_], _) = next_expr.kind;
 177                                 if next_name.ident.name == sym::next;
 178                                 if next_expr.span.ctxt() == ctxt;
 179                                 if let Some(next_id) = cx.typeck_results().type_dependent_def_id(next_expr.hir_id);
 180                                 if cx.tcx.trait_of_item(next_id) == Some(iter_id);
 181                                 then {
 182                                     next_expr.span
 183                                 } else {
 184                                     return None;
 185                                 }
 186                             }
 187                         };
 188                         match if reverse { idx ^ 1 } else { idx } {
 189                             0 => (IterUsageKind::Next, span),
 190                             1 => (IterUsageKind::Second, span),
 191                             _ => return None,
 192                         }
 193                     } else {
 194                         return None;
 195                     }
 196                 },
 197                 _ => return None,
 198             }
 199         },
 200         _ => return None,
 201     };
 202
 203     let (unwrap_kind, span) = if let Some((_, Node::Expr(e))) = iter.next() {
 204         match e.kind {
 205             ExprKind::Call(
 206                 Expr {
 207                     kind: ExprKind::Path(QPath::LangItem(LangItem::TryTraitBranch, ..)),
 208                     ..
 209                 },
 210                 _,
 211             ) => {
 212                 let parent_span = e.span.parent_callsite().unwrap();
 213                 if parent_span.ctxt() == ctxt {
 214                     (Some(UnwrapKind::QuestionMark), parent_span)
 215                 } else {
 216                     (None, span)
 217                 }
 218             },
 219             _ if e.span.ctxt() != ctxt => (None, span),
 220             ExprKind::MethodCall(name, [_], _)
 221                 if name.ident.name == sym::unwrap
 222                     && cx
 223                         .typeck_results()
 224                         .type_dependent_def_id(e.hir_id)
 225                         .map_or(false, |id| is_diag_item_method(cx, id, sym::Option)) =>
 226             {
 227                 (Some(UnwrapKind::Unwrap), e.span)
 228             },
 229             _ => (None, span),
 230         }
 231     } else {
 232         (None, span)
 233     };
 234
 235     Some(IterUsage {
 236         kind,
 237         unwrap_kind,
 238         span,
 239     })
 240 }
 241
 242 use super::NEEDLESS_SPLITN;
 243
 244 pub(super) fn check_needless_splitn(
 245     cx: &LateContext<'_>,
 246     method_name: &str,
 247     expr: &Expr<'_>,
 248     self_arg: &Expr<'_>,
 249     pat_arg: &Expr<'_>,
 250     count: u128,
 251 ) {
 252     if !cx.typeck_results().expr_ty_adjusted(self_arg).peel_refs().is_str() {
 253         return;
 254     }
 255     let ctxt = expr.span.ctxt();
 256     let mut app = Applicability::MachineApplicable;
 257     let (reverse, message) = if method_name == "splitn" {
 258         (false, "unnecessary use of `splitn`")
 259     } else {
 260         (true, "unnecessary use of `rsplitn`")
 261     };
 262     if_chain! {
 263         if count >= 2;
 264         if check_iter(cx, ctxt, cx.tcx.hir().parent_iter(expr.hir_id), count);
 265         then {
 266             span_lint_and_sugg(
 267                 cx,
 268                 NEEDLESS_SPLITN,
 269                 expr.span,
 270                 message,
 271                 "try this",
 272                 format!(
 273                     "{}.{}({})",
 274                     snippet_with_context(cx, self_arg.span, ctxt, "..", &mut app).0,
 275                     if reverse {"rsplit"} else {"split"},
 276                     snippet_with_context(cx, pat_arg.span, ctxt, "..", &mut app).0
 277                 ),
 278                 app,
 279             );
 280         }
 281     }
 282 }
 283
 284 fn check_iter<'tcx>(
 285     cx: &LateContext<'tcx>,
 286     ctxt: SyntaxContext,
 287     mut iter: impl Iterator<Item = (HirId, Node<'tcx>)>,
 288     count: u128,
 289 ) -> bool {
 290     match iter.next() {
 291         Some((_, Node::Expr(e))) if e.span.ctxt() == ctxt => {
 292             let (name, args) = if let ExprKind::MethodCall(name, [_, args @ ..], _) = e.kind {
 293                 (name, args)
 294             } else {
 295                 return false;
 296             };
 297             if_chain! {
 298                 if let Some(did) = cx.typeck_results().type_dependent_def_id(e.hir_id);
 299                 if let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator);
 300                 then {
 301                     match (name.ident.as_str(), args) {
 302                         ("next", []) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
 303                             return true;
 304                         },
 305                         ("next_tuple", []) if count > 2 => {
 306                             return true;
 307                         },
 308                         ("nth", [idx_expr]) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
 309                             if let Some((Constant::Int(idx), _)) = constant(cx, cx.typeck_results(), idx_expr) {
 310                                 if count > idx + 1 {
 311                                     return true;
 312                                 }
 313                             }
 314                         },
 315                         _ =>  return false,
 316                     }
 317                 }
 318             }
 319         },
 320         _ => return false,
 321     };
 322     false
 323 }