Noncompilable output on attribute containing string literal containing brace

[dtolnay]

As of current master (2e1a982):

$  echo 'struct x{/** */#[x="{"]x:x}' | CFG_RELEASE_CHANNEL=dev CFG_RELEASE=1 cargo run --features rustfmt --bin rustfmt

struct x {
    /** */#[x="{
    /** */
    #[x = "{"]
    x: x,
}

That output has mismatched " and some duplication of parts of the input.

It seems to do a better job if you swap "{" to "}". But my expectation would be that the formatting is the same regardless of which string is in the attribute.

$  echo 'struct x{/** */#[x="}"]x:x}' | CFG_RELEASE_CHANNEL=dev CFG_RELEASE=1 cargo run --features rustfmt --bin rustfmt

struct x {
    /** */
    #[x = "}"]
    x: x,
}

#4452 appears similar but is specific to attributes on expressions, so I am filing this separately.

[calebcartwright]

Thanks for the report. The differing behavior between opening and closing braces makes me think it's likely a bug in our searching for the body opening vs. the type of span issue that caused #4452 so agreed on separate issue 👍

Have a little free time so will look at this one shortly