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0bcacb391b
Emit simpler code from format_args
I made this PR so that `cargo expand` dumps a less overwhelming amount of formatting-related code.
<br>
`println!("rust")` **Before:**
```rust
{
::std::io::_print(::core::fmt::Arguments::new_v1(&["rust\n"],
&match () {
_args => [],
}));
};
```
**After:**
```rust
{ ::std::io::_print(::core::fmt::Arguments::new_v1(&["rust\n"], &[])); };
```
`println!("{}", x)` **Before:**
```rust
{
::std::io::_print(::core::fmt::Arguments::new_v1(
&["", "\n"],
&match (&x,) {
_args => [::core::fmt::ArgumentV1::new(
_args.0,
::core::fmt::Display::fmt,
)],
},
));
};
```
**After:**
```rust
{
::std::io::_print(::core::fmt::Arguments::new_v1(
&["", "\n"],
&[::core::fmt::ArgumentV1::new(&x, ::core::fmt::Display::fmt)],
));
};
```
The rustc_ast crate contains those things concerned purely with syntax
– that is, the AST ("abstract syntax tree"), along with some definitions for tokens and token streams, data structures/traits for mutating ASTs, and shared definitions for other AST-related parts of the compiler (like the lexer and macro-expansion).
For more information about how these things work in rustc, see the rustc dev guide: