rust-analyzer: Ambiguous "unsafe" Error WASM JS alert

I’m in the process of following the Game of Life Rust-WASM tutorial here:

https://rustwasm.github.io/docs/book/game-of-life/hello-world.html

My level of expertise in Rust: Beginner

OS: macOS Catalina 10.15.5 Editor: VSCode 1.47 rust-analyzer: v0.2.240

(rust-analyzer updated just a few minutes ago)

I’m getting this error message when looking at src/lib.rs:

{
	"resource": "[...]/wasm-game-of-life/src/lib.rs",
	"owner": "_generated_diagnostic_collection_name_#1",
	"severity": 8,
	"message": "This operation is unsafe and requires an unsafe function or block",
	"source": "rust-analyzer",
	"startLineNumber": 18,
	"startColumn": 5,
	"endLineNumber": 18,
	"endColumn": 16
}

In this code block the second alert(...) is highlighted:

#[wasm_bindgen]
extern {
    fn alert(s: &str);
}

#[wasm_bindgen]
pub fn greet(name: &str) {
    alert(name);
}

However the code compiles regardless.

When changing to:

#[wasm_bindgen]
pub fn greet(name: &str) {
    unsafe{alert(name);}
}

Then I’m getting this warning:

{
	"resource": "[...]/wasm-game-of-life/src/lib.rs",
	"owner": "_generated_diagnostic_collection_name_#1",
	"code": "unused_unsafe",
	"severity": 4,
	"message": "unnecessary `unsafe` block\n`#[warn(unused_unsafe)]` on by default",
	"source": "rustc",
	"startLineNumber": 18,
	"startColumn": 5,
	"endLineNumber": 18,
	"endColumn": 11
}

About this issue

Original URL
State: closed
Created 4 years ago
Reactions: 51
Comments: 17 (10 by maintainers)

Commits related to this issue

Merge #5682 5682: Add an option to disable diagnostics r=matklad a=popzxc As far as I know, currently it's not possible to disable a selected type of diagnostics provided by `rust-analyzer`. This... — committed to rust-lang/rust-analyzer by bors[bot] 4 years ago
Ignore missing unsafe warnings until "https://github.com/rust-analyzer/rust-analyzer/issues/5412" — committed to jaburns/dotfiles by jaburns 3 years ago
Merge #9128 9128: feat: expand procedural attribute macros r=jonas-schievink a=jonas-schievink This adds experimental support for attribute macros. They can be enabled by setting `rust-analyzer.expe... — committed to rust-lang/rust-analyzer by bors[bot] 3 years ago
Merge #9128 9128: feat: expand procedural attribute macros r=jonas-schievink a=jonas-schievink This adds experimental support for attribute macros. They can be enabled by setting `rust-analyzer.expe... — committed to rust-lang/rust-analyzer by bors[bot] 3 years ago
Remove workaround for RA issue Should be fixed or no longer applies - https://github.com/rust-analyzer/rust-analyzer/issues/5412 — committed to martin-t/rec-wars by martin-t 3 years ago

Most upvoted comments

For those looking to disable the missing-unsafe rule until it’s fixed and are using VS Code, adding the following to your settings.json and reloading your editor will suppress these errors:

"rust-analyzer.diagnostics.disabled": [
    "missing-unsafe"
]

credit to @popzxc for landing https://github.com/rust-analyzer/rust-analyzer/pull/5682, which makes the above possible

+50

FermiDirak on Sep 5, 2020

Just in case anyone doesn’t think to check the merged PR and runs into this, I can confirm that I was able to set this in VS Code and got the warning to go away:

    "rust-analyzer.experimental.procAttrMacros": true,

+22

PanopticaRising on Aug 2, 2021

You can get rid of this error / warning locally by putting an unsafe block and then surpressing the warning, but it is not a great way to handle that:

#[wasm_bindgen]
pub fn greet(name: &str) {
    #[allow(unused_unsafe)]
    unsafe {
        alert(&format!("Hello, {}!", name));
    }
}

FrankenApps on Mar 21, 2021

@OliverEvans96 cxx also uses attribute proc macros, which are not supported.

lnicola on Jan 17, 2021

Recent rust-analyzer versions should have both of those options enabled.

lnicola on Oct 17, 2021

You can enable proc-macro support using

{
    "rust-analyzer.cargo.loadOutDirsFromCheck": true,
    "rust-analyzer.procMacro.enable": true,
}

bjorn3 on Jan 17, 2021

I’d suggest listening to the rustc warning, not rust-analyzer. If the wrong diagnostics from rust-analyzer annoys you, you can also turn it off in the settings (but this currently turns all of them off).

jonas-schievink on Jul 16, 2020

That’s just because we don’t expand procedural macros yet. Presumably it does some magic to make these operations safe.

jonas-schievink on Jul 16, 2020

I just ran into this issue with cxx, which uses macros to generate safe C++ FFIs.

OliverEvans96 on Jan 17, 2021

That’s just because we don’t expand procedural macros yet. Presumably it does some magic to make these operations safe.

Would you rather recommend to get the “unsafe” error or the “unused unsafe” warning? Or in other words is my temporary ‘fix’ the right thing to do or should I just ignore it?

dgb23 on Jul 16, 2020