Last PR adjustments

[rust.git] / clippy_lints / src / casts / cast_possible_truncation.rs

diff --git a/clippy_lints/src/casts/cast_possible_truncation.rs b/clippy_lints/src/casts/cast_possible_truncation.rs
index a6376484914ba11dad3b13e0ef9fe649a9f8493c..7a6450ffaa5ec17be291ab61e854cf91b4274919 100644 (file)
--- a/clippy_lints/src/casts/cast_possible_truncation.rs
+++ b/clippy_lints/src/casts/cast_possible_truncation.rs
@@ -1,7 +1,9 @@
 use clippy_utils::consts::{constant, Constant};
-use clippy_utils::diagnostics::span_lint;
+use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
 use clippy_utils::expr_or_init;
+use clippy_utils::source::snippet;
 use clippy_utils::ty::{get_discriminant_value, is_isize_or_usize};
+use rustc_errors::{Applicability, SuggestionStyle};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{BinOpKind, Expr, ExprKind};
 use rustc_lint::LateContext;
@@ -139,7 +141,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
                 );
                 return;
             }
-            format!("casting `{cast_from}` to `{cast_to}` may truncate the value{suffix}",)
+            format!("casting `{cast_from}` to `{cast_to}` may truncate the value{suffix}")
         },
 
         (ty::Float(_), true) => {
@@ -153,5 +155,19 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
         _ => return,
     };
 
-    span_lint(cx, CAST_POSSIBLE_TRUNCATION, expr.span, &msg);
+    let snippet = snippet(cx, expr.span, "..");
+    let name_of_cast_from = snippet.split(" as").next().unwrap_or("..");
+    let suggestion = format!("{cast_to}::try_from({name_of_cast_from})");
+
+    span_lint_and_then(cx, CAST_POSSIBLE_TRUNCATION, expr.span, &msg, |diag| {
+        diag.help("if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...");
+        diag.span_suggestion_with_style(
+            expr.span,
+            "... or use `try_from` and handle the error accordingly",
+            suggestion,
+            Applicability::Unspecified,
+            // always show the suggestion in a separate line
+            SuggestionStyle::ShowAlways,
+        );
+    });
 }