Merge commit 'a5d597637dcb78dc73f93561ce474f23d4177c35' into clippyup

1 files changed, 323 insertions, 0 deletions

diff --git a/clippy_lints/src/methods/str_splitn.rs b/clippy_lints/src/methods/str_splitn.rs
new file mode 100644
index 00000000000..2595f734f11
--- /dev/null
+++ b/clippy_lints/src/methods/str_splitn.rs
@@ -0,0 +1,323 @@
+use clippy_utils::consts::{constant, Constant};
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet_with_context;
+use clippy_utils::{is_diag_item_method, match_def_path, paths};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind, HirId, LangItem, Node, QPath};
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self, adjustment::Adjust};
+use rustc_span::{symbol::sym, Span, SyntaxContext};
+
+use super::MANUAL_SPLIT_ONCE;
+
+pub(super) fn check_manual_split_once(
+    cx: &LateContext<'_>,
+    method_name: &str,
+    expr: &Expr<'_>,
+    self_arg: &Expr<'_>,
+    pat_arg: &Expr<'_>,
+) {
+    if !cx.typeck_results().expr_ty_adjusted(self_arg).peel_refs().is_str() {
+        return;
+    }
+
+    let ctxt = expr.span.ctxt();
+    let (method_name, msg, reverse) = if method_name == "splitn" {
+        ("split_once", "manual implementation of `split_once`", false)
+    } else {
+        ("rsplit_once", "manual implementation of `rsplit_once`", true)
+    };
+    let usage = match parse_iter_usage(cx, ctxt, cx.tcx.hir().parent_iter(expr.hir_id), reverse) {
+        Some(x) => x,
+        None => return,
+    };
+
+    let mut app = Applicability::MachineApplicable;
+    let self_snip = snippet_with_context(cx, self_arg.span, ctxt, "..", &mut app).0;
+    let pat_snip = snippet_with_context(cx, pat_arg.span, ctxt, "..", &mut app).0;
+
+    let sugg = match usage.kind {
+        IterUsageKind::NextTuple => {
+            format!("{}.{}({})", self_snip, method_name, pat_snip)
+        },
+        IterUsageKind::RNextTuple => format!("{}.{}({}).map(|(x, y)| (y, x))", self_snip, method_name, pat_snip),
+        IterUsageKind::Next | IterUsageKind::Second => {
+            let self_deref = {
+                let adjust = cx.typeck_results().expr_adjustments(self_arg);
+                if adjust.is_empty() {
+                    String::new()
+                } else if cx.typeck_results().expr_ty(self_arg).is_box()
+                    || adjust
+                        .iter()
+                        .any(|a| matches!(a.kind, Adjust::Deref(Some(_))) || a.target.is_box())
+                {
+                    format!("&{}", "*".repeat(adjust.len() - 1))
+                } else {
+                    "*".repeat(adjust.len() - 2)
+                }
+            };
+            if matches!(usage.kind, IterUsageKind::Next) {
+                match usage.unwrap_kind {
+                    Some(UnwrapKind::Unwrap) => {
+                        if reverse {
+                            format!("{}.{}({}).unwrap().0", self_snip, method_name, pat_snip)
+                        } else {
+                            format!(
+                                "{}.{}({}).map_or({}{}, |x| x.0)",
+                                self_snip, method_name, pat_snip, self_deref, &self_snip
+                            )
+                        }
+                    },
+                    Some(UnwrapKind::QuestionMark) => {
+                        format!(
+                            "{}.{}({}).map_or({}{}, |x| x.0)",
+                            self_snip, method_name, pat_snip, self_deref, &self_snip
+                        )
+                    },
+                    None => {
+                        format!(
+                            "Some({}.{}({}).map_or({}{}, |x| x.0))",
+                            &self_snip, method_name, pat_snip, self_deref, &self_snip
+                        )
+                    },
+                }
+            } else {
+                match usage.unwrap_kind {
+                    Some(UnwrapKind::Unwrap) => {
+                        if reverse {
+                            // In this case, no better suggestion is offered.
+                            return;
+                        }
+                        format!("{}.{}({}).unwrap().1", self_snip, method_name, pat_snip)
+                    },
+                    Some(UnwrapKind::QuestionMark) => {
+                        format!("{}.{}({})?.1", self_snip, method_name, pat_snip)
+                    },
+                    None => {
+                        format!("{}.{}({}).map(|x| x.1)", self_snip, method_name, pat_snip)
+                    },
+                }
+            }
+        },
+    };
+
+    span_lint_and_sugg(cx, MANUAL_SPLIT_ONCE, usage.span, msg, "try this", sugg, app);
+}
+
+enum IterUsageKind {
+    Next,
+    Second,
+    NextTuple,
+    RNextTuple,
+}
+
+enum UnwrapKind {
+    Unwrap,
+    QuestionMark,
+}
+
+struct IterUsage {
+    kind: IterUsageKind,
+    unwrap_kind: Option<UnwrapKind>,
+    span: Span,
+}
+
+#[allow(clippy::too_many_lines)]
+fn parse_iter_usage(
+    cx: &LateContext<'tcx>,
+    ctxt: SyntaxContext,
+    mut iter: impl Iterator<Item = (HirId, Node<'tcx>)>,
+    reverse: bool,
+) -> Option<IterUsage> {
+    let (kind, span) = match iter.next() {
+        Some((_, Node::Expr(e))) if e.span.ctxt() == ctxt => {
+            let (name, args) = if let ExprKind::MethodCall(name, _, [_, args @ ..], _) = e.kind {
+                (name, args)
+            } else {
+                return None;
+            };
+            let did = cx.typeck_results().type_dependent_def_id(e.hir_id)?;
+            let iter_id = cx.tcx.get_diagnostic_item(sym::Iterator)?;
+
+            match (&*name.ident.as_str(), args) {
+                ("next", []) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
+                    if reverse {
+                        (IterUsageKind::Second, e.span)
+                    } else {
+                        (IterUsageKind::Next, e.span)
+                    }
+                },
+                ("next_tuple", []) => {
+                    return if_chain! {
+                        if match_def_path(cx, did, &paths::ITERTOOLS_NEXT_TUPLE);
+                        if let ty::Adt(adt_def, subs) = cx.typeck_results().expr_ty(e).kind();
+                        if cx.tcx.is_diagnostic_item(sym::Option, adt_def.did);
+                        if let ty::Tuple(subs) = subs.type_at(0).kind();
+                        if subs.len() == 2;
+                        then {
+                            Some(IterUsage {
+                                kind: if reverse { IterUsageKind::RNextTuple } else { IterUsageKind::NextTuple },
+                                span: e.span,
+                                unwrap_kind: None
+                            })
+                        } else {
+                            None
+                        }
+                    };
+                },
+                ("nth" | "skip", [idx_expr]) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
+                    if let Some((Constant::Int(idx), _)) = constant(cx, cx.typeck_results(), idx_expr) {
+                        let span = if name.ident.as_str() == "nth" {
+                            e.span
+                        } else {
+                            if_chain! {
+                                if let Some((_, Node::Expr(next_expr))) = iter.next();
+                                if let ExprKind::MethodCall(next_name, _, [_], _) = next_expr.kind;
+                                if next_name.ident.name == sym::next;
+                                if next_expr.span.ctxt() == ctxt;
+                                if let Some(next_id) = cx.typeck_results().type_dependent_def_id(next_expr.hir_id);
+                                if cx.tcx.trait_of_item(next_id) == Some(iter_id);
+                                then {
+                                    next_expr.span
+                                } else {
+                                    return None;
+                                }
+                            }
+                        };
+                        match if reverse { idx ^ 1 } else { idx } {
+                            0 => (IterUsageKind::Next, span),
+                            1 => (IterUsageKind::Second, span),
+                            _ => return None,
+                        }
+                    } else {
+                        return None;
+                    }
+                },
+                _ => return None,
+            }
+        },
+        _ => return None,
+    };
+
+    let (unwrap_kind, span) = if let Some((_, Node::Expr(e))) = iter.next() {
+        match e.kind {
+            ExprKind::Call(
+                Expr {
+                    kind: ExprKind::Path(QPath::LangItem(LangItem::TryTraitBranch, _)),
+                    ..
+                },
+                _,
+            ) => {
+                let parent_span = e.span.parent_callsite().unwrap();
+                if parent_span.ctxt() == ctxt {
+                    (Some(UnwrapKind::QuestionMark), parent_span)
+                } else {
+                    (None, span)
+                }
+            },
+            _ if e.span.ctxt() != ctxt => (None, span),
+            ExprKind::MethodCall(name, _, [_], _)
+                if name.ident.name == sym::unwrap
+                    && cx
+                        .typeck_results()
+                        .type_dependent_def_id(e.hir_id)
+                        .map_or(false, |id| is_diag_item_method(cx, id, sym::Option)) =>
+            {
+                (Some(UnwrapKind::Unwrap), e.span)
+            },
+            _ => (None, span),
+        }
+    } else {
+        (None, span)
+    };
+
+    Some(IterUsage {
+        kind,
+        unwrap_kind,
+        span,
+    })
+}
+
+use super::NEEDLESS_SPLITN;
+
+pub(super) fn check_needless_splitn(
+    cx: &LateContext<'_>,
+    method_name: &str,
+    expr: &Expr<'_>,
+    self_arg: &Expr<'_>,
+    pat_arg: &Expr<'_>,
+    count: u128,
+) {
+    if !cx.typeck_results().expr_ty_adjusted(self_arg).peel_refs().is_str() {
+        return;
+    }
+    let ctxt = expr.span.ctxt();
+    let mut app = Applicability::MachineApplicable;
+    let (reverse, message) = if method_name == "splitn" {
+        (false, "unnecessary use of `splitn`")
+    } else {
+        (true, "unnecessary use of `rsplitn`")
+    };
+    if_chain! {
+        if count >= 2;
+        if check_iter(cx, ctxt, cx.tcx.hir().parent_iter(expr.hir_id), count);
+        then {
+            span_lint_and_sugg(
+                cx,
+                NEEDLESS_SPLITN,
+                expr.span,
+                message,
+                "try this",
+                format!(
+                    "{}.{}({})",
+                    snippet_with_context(cx, self_arg.span, ctxt, "..", &mut app).0,
+                    if reverse {"rsplit"} else {"split"},
+                    snippet_with_context(cx, pat_arg.span, ctxt, "..", &mut app).0
+                ),
+                app,
+            );
+        }
+    }
+}
+
+fn check_iter(
+    cx: &LateContext<'tcx>,
+    ctxt: SyntaxContext,
+    mut iter: impl Iterator<Item = (HirId, Node<'tcx>)>,
+    count: u128,
+) -> bool {
+    match iter.next() {
+        Some((_, Node::Expr(e))) if e.span.ctxt() == ctxt => {
+            let (name, args) = if let ExprKind::MethodCall(name, _, [_, args @ ..], _) = e.kind {
+                (name, args)
+            } else {
+                return false;
+            };
+            if_chain! {
+                if let Some(did) = cx.typeck_results().type_dependent_def_id(e.hir_id);
+                if let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator);
+                then {
+                    match (&*name.ident.as_str(), args) {
+                        ("next", []) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
+                            return true;
+                        },
+                        ("next_tuple", []) if count > 2 => {
+                            return true;
+                        },
+                        ("nth", [idx_expr]) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
+                            if let Some((Constant::Int(idx), _)) = constant(cx, cx.typeck_results(), idx_expr) {
+                                if count > idx + 1 {
+                                    return true;
+                                }
+                            }
+                        },
+                        _ =>  return false,
+                    }
+                }
+            }
+        },
+        _ => return false,
+    };
+    false
+}