Catch pointer::cast too in cast_ptr_alignment

[rail-rain]

Fixes #4708

Although there were some discussion in the issue, this PR implements the original feature. I think cast_ptr_alignment should exist as it is, separated from ptr_as_ptr.

---

changelog: Extend cast_ptr_alignment lint for the pointer::cast method

[rust-highfive]

r? @phansch

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[phansch]

Looks good to me in general, just got some minor improvements/refactorings =)

[phansch]

This condition can also be a part of the if_chain below

[rail-rain]

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.

[phansch]

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;
        }
    }
}

[rail-rain]

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?

[phansch]

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

[phansch]

@bors r+ thanks!

[bors]

📌 Commit 53f8731 has been approved by phansch

[bors]

⌛ Testing commit 53f8731 with merge 7f4599a...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: phansch
Pushing 7f4599a to master...