macropol 0.1.4

Ergonomic string literal interpolation in macro definitions
Documentation 
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Ergonomic string literal interpolation in macro definitions.

Replaces metavariables (`$foo`) and arbitrary expressions in string literals (including doc comments) and concatenates them with surrounding text fragments with [`core::concat!`][].

## Syntax Overview

| Syntax      | Output                       | Notes                                  |
| ----------- | ---------------------------- | -------------------------------------- |
| `"$foo"`    | `$foo`                       | `$foo` must expand to a string literal |
| `"$&foo"`   | [`core::stringify!`]`($foo)` |                                        |
| `"${bar}"`  | `bar`                        | `bar` must expand to a string literal  |

## Example

```rust
#[macropol::macropol]
macro_rules! mymacro {
    ($count:expr, $name:expr, fn $func:ident()) => {
        /// Returns `"$$ $name, $&count to beam up"`.
        fn $func() -> &'static str {
            "$$ $name, ${stringify!($count)} to beam up"
        }
    };
}

// The above definition expands to:
//
//     macro_rules! mymacro {
//         ($count:expr, $name:expr, fn $func:ident()) => {
//             #[doc = concat!("Returns `\"$ ", $name, ", ",
//                  stringify!($count), " to beam up\"`.")]
//             fn func() -> &'static str {
//                 concat!("$ ", $name, ", ",
//                     stringify!($count), " to beam up")
//             }
//         };
//     }
//

mymacro!(3, "Scotty", fn func());

assert_eq!(func(), "$ Scotty, 3 to beam up");
```

```rust
# #![cfg_attr(feature = "nightly", feature(decl_macro))]
# #[cfg(feature = "nightly")] {
#[macropol::macropol]
macro mymacro($count:expr, $name:expr, fn $func:ident()) {
    /// Returns `"$$ $name, ${stringify!($count)} to beam up"`.
    fn $func() -> &'static str {
        "$$ $name, ${stringify!($count)} to beam up"
    }
}

mymacro!(3, "Scotty", fn func());
assert_eq!(func(), "$ Scotty, 3 to beam up");
# }
```