Merge commit '0e87918536b9833bbc6c683d1f9d51ee2bf03ef1' into clippyup

[rust.git] / clippy_lints / src / as_conversions.rs

diff --git a/clippy_lints/src/as_conversions.rs b/clippy_lints/src/as_conversions.rs
index b4b02510ce7d65cc0223293f577949a3a6ccf6a6..4b31e16094e9f9a1b2d6b84bef58239698c62b8b 100644 (file)
--- a/clippy_lints/src/as_conversions.rs
+++ b/clippy_lints/src/as_conversions.rs
@@ -1,13 +1,20 @@
-use rustc::lint::in_external_macro;
+use clippy_utils::diagnostics::span_lint_and_help;
+use rustc_ast::ast::{Expr, ExprKind};
 use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
-use syntax::ast::*;
-
-use crate::utils::span_help_and_lint;
 
 declare_clippy_lint! {
     /// **What it does:** Checks for usage of `as` conversions.
     ///
+    /// Note that this lint is specialized in linting *every single* use of `as`
+    /// regardless of whether good alternatives exist or not.
+    /// If you want more precise lints for `as`, please consider using these separate lints:
+    /// `unnecessary_cast`, `cast_lossless/possible_truncation/possible_wrap/precision_loss/sign_loss`,
+    /// `fn_to_numeric_cast(_with_truncation)`, `char_lit_as_u8`, `ref_to_mut` and `ptr_as_ptr`.
+    /// There is a good explanation the reason why this lint should work in this way and how it is useful
+    /// [in this issue](https://github.com/rust-lang/rust-clippy/issues/5122).
+    ///
     /// **Why is this bad?** `as` conversions will perform many kinds of
     /// conversions, including silently lossy conversions and dangerous coercions.
     /// There are cases when it makes sense to use `as`, so the lint is
@@ -45,11 +52,12 @@ fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
         }
 
         if let ExprKind::Cast(_, _) = expr.kind {
-            span_help_and_lint(
+            span_lint_and_help(
                 cx,
                 AS_CONVERSIONS,
                 expr.span,
                 "using a potentially dangerous silent `as` conversion",
+                None,
                 "consider using a safe wrapper for this conversion",
             );
         }