Joshua Netterfield reported an ICE when the unused-parentheses lint
triggered around an async block (#54752). In order to compose an
autofixable suggestion, the lint invokes the pretty-printer on the
unnecessarily-parenthesized expression. (One wonders why the lint
doesn't just use `SourceMap::span_to_snippet` instead, to preserve the
formatting of the original source?—but for that, you'd have to ask the
author of 5c9f806d.)
But then the pretty-printer panics when trying to call `<pprust::State
as PrintState>::end` when `State.boxes` is empty. Empirically, the
problem would seem to be solved if we start some "boxes" beforehand in
the `ast::ExprKind::Async` arm of the big match in
`print_expr_outer_attr_style`, exactly like we do in the
immediately-preceding match arm for `ast::ExprKind::Block`—it would
seem pretty ("pretty") reasonable for the pretty-printing of async
blocks to work a lot like the pretty-printing of ordinary non-async
blocks, right??
Of course, it would be shamefully cargo-culty to commit code on the
basis of this kind of mere reasoning-by-analogy (in contrast to
understanding the design of the pretty-printer in such detail that the
correctness of the patch is comprehended with all the lucid certainty
of mathematical proof, rather than being merely surmised by
intuition). But maybe we care more about fixing the bug with high
probability today, than with certainty in some indefinite hypothetical
future? Maybe the effort is worth a fifth of a shirt??
Humbly resolves#54752.
Pretty print parens around casts on the LHS of `<`/`<<`
When pretty printing a cast expression occuring on the LHS of a `<` or `<<` expression, we should add parens around the cast. Otherwise, the `<`/`<<` gets interpreted as the beginning of the generics for the type on the RHS of the cast.
Consider:
$ cat parens_cast.rs
macro_rules! negative {
($e:expr) => { $e < 0 }
}
fn main() {
negative!(1 as i32);
}
Before this PR, the output of the following is not valid Rust:
$ rustc -Z unstable-options --pretty=expanded parens_cast.rs
#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std as std;
macro_rules! negative(( $ e : expr ) => { $ e < 0 });
fn main() { 1 as i32 < 0; }
After this PR, the output of the following is valid Rust:
$ rustc -Z unstable-options --pretty=expanded parens_cast.rs
#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std as std;
macro_rules! negative(( $ e : expr ) => { $ e < 0 });
fn main() { (1 as i32) < 0; }
I've gone through several README/wiki style documents but I'm still not sure where to test this though. I'm not even sure if this sort of thing is tested...
Remove attr-variant-data.rs since it relies on quirks
in legacy custom derive resolution (undefined derives
only print a warning).
Add a new test which uses a defined proc macro derive,
and tests pretty printing of proc macro derive
attributes.
Most of the Rust community agrees that the vec! macro is clearer when
called using square brackets [] instead of regular brackets (). Most of
these ocurrences are from before macros allowed using different types of
brackets.
There is one left unchanged in a pretty-print test, as the pretty
printer still wants it to have regular brackets.
This adds support to the pretty printer to print attributes
added to tuple struct elements. Furthermore, it adds a test
that makes sure we will print attributes on all variant data
types.
syntax: Always pretty print a newline after doc comments
Before this patch, code that had a doc comment as the first
line, as in:
```rust
/// Foo
struct Foo;
```
Was pretty printed into:
```rust
///Foostruct Foo;
```
This makes sure that that there is always a trailing newline
after a doc comment.
Closes#31722
Before this patch, code that had a doc comment as the first
line, as in:
```rust
/// Foo
struct Foo;
```
Was pretty printed into:
```rust
///Foostruct Foo;
```
This makes sure that that there is always a trailing newline
after a doc comment.
Closes#31722
Pretty printing of macro with braces but without terminated semicolon
removed more boxes from stack than it put there, resulting in panic.
This fixes the issue #30731.
nodes in statement position.
Extended #[cfg] folder to allow removal of statements, and
of expressions in optional positions like expression lists and trailing
block expressions.
Extended lint checker to recognize lint levels on expressions and
locals.
