Reimplement the `fn_to_numeric_cast_with_truncation` lint
This commit is contained in:
Philipp Hansch
parent
7adf24ebb0
commit
c0ab8b2531
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@ -689,6 +689,7 @@ All notable changes to this project will be documented in this file.
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[`float_cmp`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#float_cmp
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[`float_cmp_const`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#float_cmp_const
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[`fn_to_numeric_cast`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#fn_to_numeric_cast
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[`fn_to_numeric_cast_with_truncation`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#fn_to_numeric_cast_with_truncation
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[`for_kv_map`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#for_kv_map
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[`for_loop_over_option`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#for_loop_over_option
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[`for_loop_over_result`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#for_loop_over_result
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@ -9,7 +9,7 @@ We are currently in the process of discussing Clippy 1.0 via the RFC process in
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A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
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[There are 278 lints included in this crate!](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
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[There are 279 lints included in this crate!](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
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We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
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@ -698,6 +698,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
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types::CAST_PTR_ALIGNMENT,
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types::CHAR_LIT_AS_U8,
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types::FN_TO_NUMERIC_CAST,
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types::FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
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types::IMPLICIT_HASHER,
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types::LET_UNIT_VALUE,
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types::OPTION_OPTION,
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@ -791,6 +792,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
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returns::NEEDLESS_RETURN,
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strings::STRING_LIT_AS_BYTES,
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types::FN_TO_NUMERIC_CAST,
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types::FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
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types::IMPLICIT_HASHER,
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types::LET_UNIT_VALUE,
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unsafe_removed_from_name::UNSAFE_REMOVED_FROM_NAME,
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@ -746,6 +746,32 @@ declare_clippy_lint! {
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"casting a function pointer to a numeric type other than usize"
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}
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/// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
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/// store address.
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///
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/// **Why is this bad?**
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/// Such a cast discards some bits of the function's address. If this is intended, it would be more
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/// clearly expressed by casting to usize first, then casting the usize to the intended type (with
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/// a comment) to perform the truncation.
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///
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/// **Example**
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///
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/// ```rust
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/// // Bad
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/// fn fn1() -> i16 { 1 };
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/// let _ = fn1 as i32;
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///
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/// // Better: Cast to usize first, then comment with the reason for the truncation
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/// fn fn2() -> i16 { 1 };
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/// let fn_ptr = fn2 as usize;
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/// let fn_ptr_truncated = fn_ptr as i32;
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/// ```
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declare_clippy_lint! {
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pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
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style,
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"casting a function pointer to a numeric type not wide enough to store the address"
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}
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/// Returns the size in bits of an integral type.
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/// Will return 0 if the type is not an int or uint variant
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fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
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@ -1054,7 +1080,19 @@ fn lint_fn_to_numeric_cast(cx: &LateContext<'_, '_>, expr: &Expr, cast_expr: &Ex
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match cast_from.sty {
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ty::FnDef(..) | ty::FnPtr(_) => {
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let from_snippet = snippet(cx, cast_expr.span, "x");
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if cast_to.sty != ty::Uint(UintTy::Usize) {
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let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
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if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
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span_lint_and_sugg(
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cx,
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FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
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expr.span,
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&format!("casting function pointer `{}` to `{}`, which truncates the value", from_snippet, cast_to),
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"try",
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format!("{} as usize", from_snippet)
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);
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} else if cast_to.sty != ty::Uint(UintTy::Usize) {
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span_lint_and_sugg(
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cx,
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FN_TO_NUMERIC_CAST,
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@ -1,6 +1,6 @@
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#![feature(tool_lints)]
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#[warn(clippy::fn_to_numeric_cast)]
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#![warn(clippy::fn_to_numeric_cast)]
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fn foo() -> String { String::new() }
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@ -0,0 +1,142 @@
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error: casting function pointer `foo` to `i8`
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--> $DIR/fn_to_numeric_cast.rs:8:13
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8 | let _ = foo as i8;
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| ^^^^^^^^^ help: try: `foo as usize`
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= note: `-D clippy::fn-to-numeric-cast` implied by `-D warnings`
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error: casting function pointer `foo` to `i16`
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--> $DIR/fn_to_numeric_cast.rs:9:13
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9 | let _ = foo as i16;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `i32`
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--> $DIR/fn_to_numeric_cast.rs:10:13
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10 | let _ = foo as i32;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `i64`
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--> $DIR/fn_to_numeric_cast.rs:11:13
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11 | let _ = foo as i64;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `i128`
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--> $DIR/fn_to_numeric_cast.rs:12:13
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12 | let _ = foo as i128;
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| ^^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `isize`
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--> $DIR/fn_to_numeric_cast.rs:13:13
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13 | let _ = foo as isize;
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| ^^^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `u8`
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--> $DIR/fn_to_numeric_cast.rs:15:13
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15 | let _ = foo as u8;
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| ^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `u16`
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--> $DIR/fn_to_numeric_cast.rs:16:13
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16 | let _ = foo as u16;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `u32`
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--> $DIR/fn_to_numeric_cast.rs:17:13
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17 | let _ = foo as u32;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `u64`
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--> $DIR/fn_to_numeric_cast.rs:18:13
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18 | let _ = foo as u64;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `u128`
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--> $DIR/fn_to_numeric_cast.rs:19:13
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19 | let _ = foo as u128;
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| ^^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `abc` to `i8`
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--> $DIR/fn_to_numeric_cast.rs:28:13
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28 | let _ = abc as i8;
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| ^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `i16`
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--> $DIR/fn_to_numeric_cast.rs:29:13
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29 | let _ = abc as i16;
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| ^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `i32`
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--> $DIR/fn_to_numeric_cast.rs:30:13
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30 | let _ = abc as i32;
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| ^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `i64`
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--> $DIR/fn_to_numeric_cast.rs:31:13
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31 | let _ = abc as i64;
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| ^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `i128`
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--> $DIR/fn_to_numeric_cast.rs:32:13
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32 | let _ = abc as i128;
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| ^^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `isize`
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--> $DIR/fn_to_numeric_cast.rs:33:13
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33 | let _ = abc as isize;
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| ^^^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `u8`
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--> $DIR/fn_to_numeric_cast.rs:35:13
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35 | let _ = abc as u8;
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| ^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `u16`
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--> $DIR/fn_to_numeric_cast.rs:36:13
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36 | let _ = abc as u16;
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| ^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `u32`
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--> $DIR/fn_to_numeric_cast.rs:37:13
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37 | let _ = abc as u32;
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| ^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `u64`
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--> $DIR/fn_to_numeric_cast.rs:38:13
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38 | let _ = abc as u64;
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| ^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `abc` to `u128`
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--> $DIR/fn_to_numeric_cast.rs:39:13
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39 | let _ = abc as u128;
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| ^^^^^^^^^^^ help: try: `abc as usize`
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error: casting function pointer `f` to `i32`
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--> $DIR/fn_to_numeric_cast.rs:46:5
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46 | f as i32
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| ^^^^^^^^ help: try: `f as usize`
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error: aborting due to 23 previous errors
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@ -0,0 +1,23 @@
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#![feature(tool_lints)]
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#![warn(clippy::fn_to_numeric_cast_with_truncation)]
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#![allow(clippy::fn_to_numeric_cast)]
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fn foo() -> String { String::new() }
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fn test_fn_to_numeric_cast_with_truncation() {
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let _ = foo as i8;
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let _ = foo as i16;
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let _ = foo as i32;
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let _ = foo as u8;
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let _ = foo as u16;
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let _ = foo as u32;
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// TODO: Is it bad to have these tests?
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// Running the tests on a different architechture will
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// produce different results
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let _ = foo as u64;
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let _ = foo as i64;
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}
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fn main() {}
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@ -0,0 +1,40 @@
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error: casting function pointer `foo` to `i8`, which truncates the value
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--> $DIR/fn_to_numeric_cast_with_truncation.rs:9:13
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9 | let _ = foo as i8;
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| ^^^^^^^^^ help: try: `foo as usize`
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= note: `-D clippy::fn-to-numeric-cast-with-truncation` implied by `-D warnings`
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error: casting function pointer `foo` to `i16`, which truncates the value
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--> $DIR/fn_to_numeric_cast_with_truncation.rs:10:13
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10 | let _ = foo as i16;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `i32`, which truncates the value
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--> $DIR/fn_to_numeric_cast_with_truncation.rs:11:13
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11 | let _ = foo as i32;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `u8`, which truncates the value
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--> $DIR/fn_to_numeric_cast_with_truncation.rs:12:13
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12 | let _ = foo as u8;
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| ^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `u16`, which truncates the value
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--> $DIR/fn_to_numeric_cast_with_truncation.rs:13:13
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13 | let _ = foo as u16;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: casting function pointer `foo` to `u32`, which truncates the value
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--> $DIR/fn_to_numeric_cast_with_truncation.rs:14:13
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14 | let _ = foo as u32;
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| ^^^^^^^^^^ help: try: `foo as usize`
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error: aborting due to 6 previous errors
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