Address PR reivew

Author: xFrednet

clippy_lints/src/casts/cast_possible_truncation.rs

@@ -8,6 +8,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{BinOpKind, Expr, ExprKind};
 use rustc_lint::LateContext;
 use rustc_middle::ty::{self, FloatTy, Ty};
+use rustc_span::Span;
 use rustc_target::abi::IntegerType;
 
 use super::{utils, CAST_ENUM_TRUNCATION, CAST_POSSIBLE_TRUNCATION};
@@ -76,7 +77,14 @@ fn apply_reductions(cx: &LateContext<'_>, nbits: u64, expr: &Expr<'_>, signed: b
     }
 }
 
-pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
+pub(super) fn check(
+    cx: &LateContext<'_>,
+    expr: &Expr<'_>,
+    cast_expr: &Expr<'_>,
+    cast_from: Ty<'_>,
+    cast_to: Ty<'_>,
+    cast_to_span: Span,
+) {
     let msg = match (cast_from.kind(), cast_to.is_integral()) {
         (ty::Int(_) | ty::Uint(_), true) => {
             let from_nbits = apply_reductions(
@@ -155,9 +163,9 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
         _ => return,
     };
 
-    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})");
+    let name_of_cast_from = snippet(cx, cast_expr.span, "..");
+    let cast_to_snip = snippet(cx, cast_to_span, "..");
+    let suggestion = format!("{cast_to_snip}::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)]` ...");

clippy_lints/src/casts/mod.rs

@@ -728,7 +728,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
             fn_to_numeric_cast_with_truncation::check(cx, expr, cast_expr, cast_from, cast_to);
 
             if cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
-                cast_possible_truncation::check(cx, expr, cast_expr, cast_from, cast_to);
+                cast_possible_truncation::check(cx, expr, cast_expr, cast_from, cast_to, cast_to_hir.span);
                 if cast_from.is_numeric() {
                     cast_possible_wrap::check(cx, expr, cast_from, cast_to);
                     cast_precision_loss::check(cx, expr, cast_from, cast_to);

tests/ui/cast.rs

@@ -28,6 +28,7 @@ fn main() {
     1i32 as u8;
     1f64 as isize;
     1f64 as usize;
+    1f32 as u32 as u16;
     // Test clippy::cast_possible_wrap
     1u8 as i8;
     1u16 as i16;

tests/ui/cast.stderr

@@ -135,52 +135,82 @@ error: casting `f64` to `usize` may lose the sign of the value
 LL |     1f64 as usize;
    |     ^^^^^^^^^^^^^
 
+error: casting `u32` to `u16` may truncate the value
+  --> $DIR/cast.rs:31:5
+   |
+LL |     1f32 as u32 as u16;
+   |     ^^^^^^^^^^^^^^^^^^
+   |
+   = help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
+help: ... or use `try_from` and handle the error accordingly
+   |
+LL |     u16::try_from(1f32 as u32);
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: casting `f32` to `u32` may truncate the value
+  --> $DIR/cast.rs:31:5
+   |
+LL |     1f32 as u32 as u16;
+   |     ^^^^^^^^^^^
+   |
+   = help: if this is intentional allow the lint with `#[allow(clippy::cast_precision_loss)]` ...
+help: ... or use `try_from` and handle the error accordingly
+   |
+LL |     u32::try_from(1f32) as u16;
+   |     ~~~~~~~~~~~~~~~~~~~
+
+error: casting `f32` to `u32` may lose the sign of the value
+  --> $DIR/cast.rs:31:5
+   |
+LL |     1f32 as u32 as u16;
+   |     ^^^^^^^^^^^
+
 error: casting `u8` to `i8` may wrap around the value
-  --> $DIR/cast.rs:32:5
+  --> $DIR/cast.rs:33:5
    |
 LL |     1u8 as i8;
    |     ^^^^^^^^^
    |
    = note: `-D clippy::cast-possible-wrap` implied by `-D warnings`
 
 error: casting `u16` to `i16` may wrap around the value
-  --> $DIR/cast.rs:33:5
+  --> $DIR/cast.rs:34:5
    |
 LL |     1u16 as i16;
    |     ^^^^^^^^^^^
 
 error: casting `u32` to `i32` may wrap around the value
-  --> $DIR/cast.rs:34:5
+  --> $DIR/cast.rs:35:5
    |
 LL |     1u32 as i32;
    |     ^^^^^^^^^^^
 
 error: casting `u64` to `i64` may wrap around the value
-  --> $DIR/cast.rs:35:5
+  --> $DIR/cast.rs:36:5
    |
 LL |     1u64 as i64;
    |     ^^^^^^^^^^^
 
 error: casting `usize` to `isize` may wrap around the value
-  --> $DIR/cast.rs:36:5
+  --> $DIR/cast.rs:37:5
    |
 LL |     1usize as isize;
    |     ^^^^^^^^^^^^^^^
 
 error: casting `i32` to `u32` may lose the sign of the value
-  --> $DIR/cast.rs:39:5
+  --> $DIR/cast.rs:40:5
    |
 LL |     -1i32 as u32;
    |     ^^^^^^^^^^^^
 
 error: casting `isize` to `usize` may lose the sign of the value
-  --> $DIR/cast.rs:41:5
+  --> $DIR/cast.rs:42:5
    |
 LL |     -1isize as usize;
    |     ^^^^^^^^^^^^^^^^
 
 error: casting `i64` to `i8` may truncate the value
-  --> $DIR/cast.rs:108:5
+  --> $DIR/cast.rs:109:5
    |
 LL |     (-99999999999i64).min(1) as i8; // should be linted because signed
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -192,7 +222,7 @@ LL |     i8::try_from((-99999999999i64).min(1)); // should be linted because sig
    |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: casting `u64` to `u8` may truncate the value
-  --> $DIR/cast.rs:120:5
+  --> $DIR/cast.rs:121:5
    |
 LL |     999999u64.clamp(0, 256) as u8; // should still be linted
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -204,7 +234,7 @@ LL |     u8::try_from(999999u64.clamp(0, 256)); // should still be linted
    |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: casting `main::E2` to `u8` may truncate the value
-  --> $DIR/cast.rs:141:21
+  --> $DIR/cast.rs:142:21
    |
 LL |             let _ = self as u8;
    |                     ^^^^^^^^^^
@@ -216,15 +246,15 @@ LL |             let _ = u8::try_from(self);
    |                     ~~~~~~~~~~~~~~~~~~
 
 error: casting `main::E2::B` to `u8` will truncate the value
-  --> $DIR/cast.rs:142:21
+  --> $DIR/cast.rs:143:21
    |
 LL |             let _ = Self::B as u8;
    |                     ^^^^^^^^^^^^^
    |
    = note: `-D clippy::cast-enum-truncation` implied by `-D warnings`
 
 error: casting `main::E5` to `i8` may truncate the value
-  --> $DIR/cast.rs:178:21
+  --> $DIR/cast.rs:179:21
    |
 LL |             let _ = self as i8;
    |                     ^^^^^^^^^^
@@ -236,13 +266,13 @@ LL |             let _ = i8::try_from(self);
    |                     ~~~~~~~~~~~~~~~~~~
 
 error: casting `main::E5::A` to `i8` will truncate the value
-  --> $DIR/cast.rs:179:21
+  --> $DIR/cast.rs:180:21
    |
 LL |             let _ = Self::A as i8;
    |                     ^^^^^^^^^^^^^
 
 error: casting `main::E6` to `i16` may truncate the value
-  --> $DIR/cast.rs:193:21
+  --> $DIR/cast.rs:194:21
    |
 LL |             let _ = self as i16;
    |                     ^^^^^^^^^^^
@@ -254,7 +284,7 @@ LL |             let _ = i16::try_from(self);
    |                     ~~~~~~~~~~~~~~~~~~~
 
 error: casting `main::E7` to `usize` may truncate the value on targets with 32-bit wide pointers
-  --> $DIR/cast.rs:208:21
+  --> $DIR/cast.rs:209:21
    |
 LL |             let _ = self as usize;
    |                     ^^^^^^^^^^^^^
@@ -266,7 +296,7 @@ LL |             let _ = usize::try_from(self);
    |                     ~~~~~~~~~~~~~~~~~~~~~
 
 error: casting `main::E10` to `u16` may truncate the value
-  --> $DIR/cast.rs:249:21
+  --> $DIR/cast.rs:250:21
    |
 LL |             let _ = self as u16;
    |                     ^^^^^^^^^^^
@@ -278,7 +308,7 @@ LL |             let _ = u16::try_from(self);
    |                     ~~~~~~~~~~~~~~~~~~~
 
 error: casting `u32` to `u8` may truncate the value
-  --> $DIR/cast.rs:257:13
+  --> $DIR/cast.rs:258:13
    |
 LL |     let c = (q >> 16) as u8;
    |             ^^^^^^^^^^^^^^^
@@ -290,7 +320,7 @@ LL |     let c = u8::try_from((q >> 16));
    |             ~~~~~~~~~~~~~~~~~~~~~~~
 
 error: casting `u32` to `u8` may truncate the value
-  --> $DIR/cast.rs:260:13
+  --> $DIR/cast.rs:261:13
    |
 LL |     let c = (q / 1000) as u8;
    |             ^^^^^^^^^^^^^^^^
@@ -301,5 +331,5 @@ help: ... or use `try_from` and handle the error accordingly
 LL |     let c = u8::try_from((q / 1000));
    |             ~~~~~~~~~~~~~~~~~~~~~~~~
 
-error: aborting due to 33 previous errors
+error: aborting due to 36 previous errors