Inconsistent formatting between functions and function-like macros

Rustfmt accepts the following code without issues:

pub const FOO: &str = foo("
    foo
    bar
");

But if we are to replace foo with a function-like macro:

pub const FOO: &str = foo!("
    foo
    bar
");

Rustfmt wants to reformat it as:

pub const FOO: &str = foo!(
    "
    foo
    bar
"
);

The resulting formatting is far from beautiful, space inefficient, and inconsistent with how rustfmt handles functions.

This issue is quite annoying in practice for example when code uses the hex-literal crate.

Start by reproducing the two Rust examples with rustfmt and compare how function calls and function-like macros are formatted. No source files or tests are named; done means the macro form preserves the compact string formatting used for the equivalent function call.