is_expr_identity_of_pat: simplify using (unordered_)over (#15450)

This makes the last arm significantly shorter, but marginally shortens
the other ones as well

- I first removed the length comparisons from the match guards since
they were already present in `(unordered_)over`, but then brought them
back since they are quite a helpful "guard clause"
- It's a bit unfortunate that the `Slice`/`Array` arm can't use `over`
as well, which creates some asymmetry, but changing the signature of
`over` to accept arbitrary iterators felt like too much to me,
especially because we'd lose the ability to compare the lengths of the
two inputs (which could've been mitigated by `ExactLenIterator::len`,
but that method is still unstable AFAIR)

One other option would be to only use `unordered_over` in the last arm,
and not `over`, but I think `over` is not that bad..

changelog: none

Author: samueltardieu

clippy_utils/src/ast_utils/mod.rs

@@ -21,7 +21,7 @@ pub fn is_useless_with_eq_exprs(kind: BinOpKind) -> bool {
 }
 
 /// Checks if each element in the first slice is contained within the latter as per `eq_fn`.
-pub fn unordered_over<X>(left: &[X], right: &[X], mut eq_fn: impl FnMut(&X, &X) -> bool) -> bool {
+pub fn unordered_over<X, Y>(left: &[X], right: &[Y], mut eq_fn: impl FnMut(&X, &Y) -> bool) -> bool {
     left.len() == right.len() && left.iter().all(|l| right.iter().any(|r| eq_fn(l, r)))
 }
 

clippy_utils/src/hir_utils.rs

@@ -757,7 +757,7 @@ pub fn both_some_and<X, Y>(l: Option<X>, r: Option<Y>, mut pred: impl FnMut(X, Y
 }
 
 /// Checks if two slices are equal as per `eq_fn`.
-pub fn over<X>(left: &[X], right: &[X], mut eq_fn: impl FnMut(&X, &X) -> bool) -> bool {
+pub fn over<X, Y>(left: &[X], right: &[Y], mut eq_fn: impl FnMut(&X, &Y) -> bool) -> bool {
     left.len() == right.len() && left.iter().zip(right).all(|(x, y)| eq_fn(x, y))
 }
 

clippy_utils/src/lib.rs

@@ -126,6 +126,7 @@ use rustc_span::{InnerSpan, Span};
 use source::{SpanRangeExt, walk_span_to_context};
 use visitors::{Visitable, for_each_unconsumed_temporary};
 
+use crate::ast_utils::unordered_over;
 use crate::consts::{ConstEvalCtxt, Constant, mir_to_const};
 use crate::higher::Range;
 use crate::ty::{adt_and_variant_of_res, can_partially_move_ty, expr_sig, is_copy, is_recursively_primitive_type};
@@ -1992,7 +1993,7 @@ pub fn is_expr_identity_of_pat(cx: &LateContext<'_>, pat: &Pat<'_>, expr: &Expr<
         (PatKind::Tuple(pats, dotdot), ExprKind::Tup(tup))
             if dotdot.as_opt_usize().is_none() && pats.len() == tup.len() =>
         {
-            zip(pats, tup).all(|(pat, expr)| is_expr_identity_of_pat(cx, pat, expr, by_hir))
+            over(pats, tup, |pat, expr| is_expr_identity_of_pat(cx, pat, expr, by_hir))
         },
         (PatKind::Slice(before, None, after), ExprKind::Array(arr)) if before.len() + after.len() == arr.len() => {
             zip(before.iter().chain(after), arr).all(|(pat, expr)| is_expr_identity_of_pat(cx, pat, expr, by_hir))
@@ -2004,7 +2005,7 @@ pub fn is_expr_identity_of_pat(cx: &LateContext<'_>, pat: &Pat<'_>, expr: &Expr<
             if let ExprKind::Path(ident) = &ident.kind
                 && qpath_res(&pat_ident, pat.hir_id) == qpath_res(ident, expr.hir_id)
                 // check fields
-                && zip(field_pats, fields).all(|(pat, expr)| is_expr_identity_of_pat(cx, pat, expr,by_hir))
+                && over(field_pats, fields, |pat, expr| is_expr_identity_of_pat(cx, pat, expr,by_hir))
             {
                 true
             } else {
@@ -2017,10 +2018,8 @@ pub fn is_expr_identity_of_pat(cx: &LateContext<'_>, pat: &Pat<'_>, expr: &Expr<
             // check ident
             qpath_res(&pat_ident, pat.hir_id) == qpath_res(ident, expr.hir_id)
                 // check fields
-                && field_pats.iter().all(|field_pat| {
-                    fields.iter().any(|field| {
-                        field_pat.ident == field.ident && is_expr_identity_of_pat(cx, field_pat.pat, field.expr, by_hir)
-                    })
+                && unordered_over(field_pats, fields, |field_pat, field| {
+                    field_pat.ident == field.ident && is_expr_identity_of_pat(cx, field_pat.pat, field.expr, by_hir)
                 })
         },
         _ => false,