Pull is_full_range method from iter_with_drain

Rename method to `is_range_full` because the type is actually
`RangeFull`.

Method moved to `clippy_utils` for reuse in `clear_with_drain`.

clippy_lints/src/methods/iter_with_drain.rs

@@ -1,9 +1,8 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::higher::Range;
-use clippy_utils::is_integer_const;
+use clippy_utils::is_range_full;
-use rustc_ast::ast::RangeLimits;
 use rustc_errors::Applicability;
-use rustc_hir::{Expr, ExprKind, QPath};
+use rustc_hir::{Expr, ExprKind};
 use rustc_lint::LateContext;
 use rustc_span::symbol::sym;
 use rustc_span::Span;
@@ -16,7 +15,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span
         && let Some(ty_name) = cx.tcx.get_diagnostic_name(adt.did())
         && matches!(ty_name, sym::Vec | sym::VecDeque)
         && let Some(range) = Range::hir(arg)
-        && is_full_range(cx, recv, range)
+        && is_range_full(cx, recv, range)
     {
         span_lint_and_sugg(
             cx,
@@ -29,19 +28,3 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span
         );
     };
 }
-
-fn is_full_range(cx: &LateContext<'_>, container: &Expr<'_>, range: Range<'_>) -> bool {
-    range.start.map_or(true, |e| is_integer_const(cx, e, 0))
-        && range.end.map_or(true, |e| {
-            if range.limits == RangeLimits::HalfOpen
-                && let ExprKind::Path(QPath::Resolved(None, container_path)) = container.kind
-                && let ExprKind::MethodCall(name, self_arg, [], _) = e.kind
-                && name.ident.name == sym::len
-                && let ExprKind::Path(QPath::Resolved(None, path)) = self_arg.kind
-            {
-                container_path.res == path.res
-            } else {
-                false
-            }
-        })
-}

clippy_utils/src/lib.rs

@@ -78,7 +78,7 @@ use std::sync::OnceLock;
 use std::sync::{Mutex, MutexGuard};
 
 use if_chain::if_chain;
-use rustc_ast::ast::{self, LitKind};
+use rustc_ast::ast::{self, LitKind, RangeLimits};
 use rustc_ast::Attribute;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::unhash::UnhashMap;
@@ -115,6 +115,7 @@ use rustc_span::Span;
 use rustc_target::abi::Integer;
 
 use crate::consts::{constant, Constant};
+use crate::higher::Range;
 use crate::ty::{can_partially_move_ty, expr_sig, is_copy, is_recursively_primitive_type, ty_is_fn_once_param};
 use crate::visitors::for_each_expr;
 
@@ -1491,6 +1492,24 @@ pub fn is_else_clause(tcx: TyCtxt<'_>, expr: &Expr<'_>) -> bool {
     }
 }
 
+/// Checks whether the given `Range` is equivalent to a `RangeFull`.
+/// Inclusive ranges are not considered because they already constitute a lint.
+pub fn is_range_full(cx: &LateContext<'_>, container: &Expr<'_>, range: Range<'_>) -> bool {
+    range.start.map_or(true, |e| is_integer_const(cx, e, 0))
+        && range.end.map_or(true, |e| {
+            if range.limits == RangeLimits::HalfOpen
+                && let ExprKind::Path(QPath::Resolved(None, container_path)) = container.kind
+                && let ExprKind::MethodCall(name, self_arg, [], _) = e.kind
+                && name.ident.name == sym::len
+                && let ExprKind::Path(QPath::Resolved(None, path)) = self_arg.kind
+            {
+                container_path.res == path.res
+            } else {
+                false
+            }
+        })
+}
+
 /// Checks whether the given expression is a constant integer of the given value.
 /// unlike `is_integer_literal`, this version does const folding
 pub fn is_integer_const(cx: &LateContext<'_>, e: &Expr<'_>, value: u128) -> bool {