Merge tag 'debian/1.52.1+dfsg1-1_exp2' into proxmox/buster

[rustc.git] / src / tools / clippy / clippy_lints / src / casts / fn_to_numeric_cast_with_truncation.rs

diff --git a/src/tools/clippy/clippy_lints/src/casts/fn_to_numeric_cast_with_truncation.rs b/src/tools/clippy/clippy_lints/src/casts/fn_to_numeric_cast_with_truncation.rs
new file mode 100644 (file)
index 0000000..0085c7b
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/casts/fn_to_numeric_cast_with_truncation.rs
@@ -0,0 +1,39 @@
+use rustc_errors::Applicability;
+use rustc_hir::Expr;
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self, Ty};
+
+use crate::utils::{snippet_with_applicability, span_lint_and_sugg};
+
+use super::{utils, FN_TO_NUMERIC_CAST_WITH_TRUNCATION};
+
+pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
+    // We only want to check casts to `ty::Uint` or `ty::Int`
+    match cast_to.kind() {
+        ty::Uint(_) | ty::Int(..) => { /* continue on */ },
+        _ => return,
+    }
+    match cast_from.kind() {
+        ty::FnDef(..) | ty::FnPtr(_) => {
+            let mut applicability = Applicability::MaybeIncorrect;
+            let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
+
+            let to_nbits = utils::int_ty_to_nbits(cast_to, cx.tcx);
+            if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
+                span_lint_and_sugg(
+                    cx,
+                    FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
+                    expr.span,
+                    &format!(
+                        "casting function pointer `{}` to `{}`, which truncates the value",
+                        from_snippet, cast_to
+                    ),
+                    "try",
+                    format!("{} as usize", from_snippet),
+                    applicability,
+                );
+            }
+        },
+        _ => {},
+    }
+}