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Catch pointer::cast too in cast_ptr_alignment #6557

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merged 3 commits into from
Jan 11, 2021
Merged

Catch pointer::cast too in cast_ptr_alignment #6557

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f50ded0
Catch `pointer::cast` too in `cast_ptr_alignment`
rail-rain Jan 7, 2021
ee9b47d
Move `is_hir_ty_cfg_dependant` to `util`,
rail-rain Jan 8, 2021
53f8731
Simplify `cast_ptr_alignment` `pointer::casr` case
rail-rain Jan 11, 2021
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35 changes: 29 additions & 6 deletions clippy_lints/src/types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1637,12 +1637,8 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
return;
}
if let ExprKind::Cast(ref ex, cast_to) = expr.kind {
if let TyKind::Path(QPath::Resolved(_, path)) = cast_to.kind {
if let Res::Def(_, def_id) = path.res {
if cx.tcx.has_attr(def_id, sym::cfg) || cx.tcx.has_attr(def_id, sym::cfg_attr) {
return;
}
}
if is_hir_ty_cfg_dependant(cx, cast_to) {
return;
}
let (cast_from, cast_to) = (cx.typeck_results().expr_ty(ex), cx.typeck_results().expr_ty(expr));
lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
Expand Down Expand Up @@ -1691,6 +1687,21 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
lint_numeric_casts(cx, expr, ex, cast_from, cast_to);
}

lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
} else if let ExprKind::MethodCall(method_path, _, args, _) = expr.kind {
if method_path.ident.name != sym!(cast) {
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This condition can also be a part of the if_chain below

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Sorry, I'm not sure if I know what you mean.

Does it look like this:

if let ExprKind::Cast(ref ex, cast_to) = expr.kind {
    ...
    lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
} else if let ExprKind::MethodCall(method_path, _, args, _) = expr.kind {
    if_chain! {
        if method_path.ident.name == sym!(cast);
        if let Some(generic_args) = method_path.args;
        if let [GenericArg::Type(cast_to)] = generic_args.args;
        // There probably is no obvious reason to do this, just to be consistent with `as` cases.
        if !is_hir_ty_cfg_dependant(cx, cast_to);
        then {
            let (cast_from, cast_to) =
                (cx.typeck_results().expr_ty(&args[0]), cx.typeck_results().expr_ty(expr));
            lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
        }
    }

or this?:

if let ExprKind::Cast(ref ex, cast_to) = expr.kind {
    ...
    lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
}

if_chain! {
    if let ExprKind::MethodCall(method_path, _, args, _) = expr.kind;
    if method_path.ident.name == sym!(cast);
    if let Some(generic_args) = method_path.args;
    if let [GenericArg::Type(cast_to)] = generic_args.args;
    // There probably is no obvious reason to do this, just to be consistent with `as` cases.
    if !is_hir_ty_cfg_dependant(cx, cast_to);
    then {
        let (cast_from, cast_to) = (cx.typeck_results().expr_ty(&args[0]), cx.typeck_results().expr_ty(expr));
        lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
    }
}

Both look better than the current one though.

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I had this in mind:

if let ExprKind::Cast(ref ex, cast_to) = expr.kind {
    ...
    lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
} else if let ExprKind::MethodCall(method_path, _, args, _) = expr.kind {
    if_chain! {
        if method_path.ident.name != sym!(cast);
        if let Some(generic_args) = method_path.args;
        if let [GenericArg::Type(cast_to)] = generic_args.args;
        // There probably is no obvious reason to do this, just to be consistent with `as` cases.
        if is_hir_ty_cfg_dependant(cx, cast_to);
        then {
            return;
        }
    }
}

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So, my guess was not so far away. Since there will be only one if_chain!, I think my first one is the best. What do you think?

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Oh yes I must have misunderstood it the first time, that's indeed better =)

return;
}
if_chain! {
if let Some(generic_args) = method_path.args;
if let [GenericArg::Type(cast_to)] = generic_args.args;
// There probably is no obvious reason to do this, just to be consistent with `as` cases.
if is_hir_ty_cfg_dependant(cx, cast_to);
then {
return;
}
}
let (cast_from, cast_to) = (cx.typeck_results().expr_ty(&args[0]), cx.typeck_results().expr_ty(expr));
lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
}
}
Expand All @@ -1714,6 +1725,18 @@ fn get_numeric_literal<'e>(expr: &'e Expr<'e>) -> Option<&'e Lit> {
}
}

fn is_hir_ty_cfg_dependant(cx: &LateContext<'_>, ty: &hir::Ty<'_>) -> bool {
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if_chain! {
if let TyKind::Path(QPath::Resolved(_, path)) = ty.kind;
if let Res::Def(_, def_id) = path.res;
then {
cx.tcx.has_attr(def_id, sym::cfg) || cx.tcx.has_attr(def_id, sym::cfg_attr)
} else {
false
}
}
}

fn show_unnecessary_cast(cx: &LateContext<'_>, expr: &Expr<'_>, literal_str: &str, cast_from: Ty<'_>, cast_to: Ty<'_>) {
let literal_kind_name = if cast_from.is_integral() { "integer" } else { "float" };
span_lint_and_sugg(
Expand Down
4 changes: 4 additions & 0 deletions tests/ui/cast_alignment.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,10 @@ fn main() {
(&1u8 as *const u8) as *const u16;
(&mut 1u8 as *mut u8) as *mut u16;

// cast to more-strictly-aligned type, but with the `pointer::cast` function.
(&1u8 as *const u8).cast::<u16>();
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(&mut 1u8 as *mut u8).cast::<u16>();

/* These should be ok */

// not a pointer type
Expand Down
14 changes: 13 additions & 1 deletion tests/ui/cast_alignment.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -12,5 +12,17 @@ error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1
LL | (&mut 1u8 as *mut u8) as *mut u16;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors
error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`) (1 < 2 bytes)
--> $DIR/cast_alignment.rs:15:5
|
LL | (&1u8 as *const u8).cast::<u16>();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1 < 2 bytes)
--> $DIR/cast_alignment.rs:16:5
|
LL | (&mut 1u8 as *mut u8).cast::<u16>();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 4 previous errors