1 files changed, 48 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/methods/seek_from_current.rs b/src/tools/clippy/clippy_lints/src/methods/seek_from_current.rs
new file mode 100644
index 000000000..361a3082f
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/methods/seek_from_current.rs
@@ -0,0 +1,48 @@
+use rustc_ast::ast::{LitIntType, LitKind};
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::LateContext;
+
+use clippy_utils::{
+    diagnostics::span_lint_and_sugg, get_trait_def_id, match_def_path, paths, source::snippet_with_applicability,
+    ty::implements_trait,
+};
+
+use super::SEEK_FROM_CURRENT;
+
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, recv: &'tcx Expr<'_>, arg: &'tcx Expr<'_>) {
+    let ty = cx.typeck_results().expr_ty(recv);
+
+    if let Some(def_id) = get_trait_def_id(cx, &paths::STD_IO_SEEK) {
+        if implements_trait(cx, ty, def_id, &[]) && arg_is_seek_from_current(cx, arg) {
+            let mut applicability = Applicability::MachineApplicable;
+            let snip = snippet_with_applicability(cx, recv.span, "..", &mut applicability);
+
+            span_lint_and_sugg(
+                cx,
+                SEEK_FROM_CURRENT,
+                expr.span,
+                "using `SeekFrom::Current` to start from current position",
+                "replace with",
+                format!("{snip}.stream_position()"),
+                applicability,
+            );
+        }
+    }
+}
+
+fn arg_is_seek_from_current<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
+    if let ExprKind::Call(f, args) = expr.kind &&
+        let ExprKind::Path(ref path) = f.kind &&
+        let Some(def_id) = cx.qpath_res(path, f.hir_id).opt_def_id() &&
+        match_def_path(cx, def_id, &paths::STD_IO_SEEK_FROM_CURRENT) {
+        // check if argument of `SeekFrom::Current` is `0`
+        if args.len() == 1 &&
+            let ExprKind::Lit(ref lit) = args[0].kind &&
+            let LitKind::Int(0, LitIntType::Unsuffixed) = lit.node {
+            return true
+        }
+    }
+
+    false
+}