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Commitd3debc0

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Rollup merge of#126929 - nnethercote:rm-__rust_force_expr, r=oli-obk
Remove `__rust_force_expr`.This was added (with a different name) to improve an error message. It is no longer needed -- removing it changes the error message, but overall I think the new message is no worse:- the mention of `#` in the first line is a little worse,- but the extra context makes it very clear what the problem is, perhaps even clearer than the old message,- and the removal of the note about the `expr` fragment (an internal detail of `__rust_force_expr`) is an improvement.Overall I think the error is quite clear and still far better than the old message that prompted#61933, which didn't even mention patterns.The motivation for this is#124141, which will cause pasted metavariables to be tokenized and reparsed instead of the AST node being cached. This change in behaviour occasionally has a non-zero perf cost, and `__rust_force_expr` causes the tokenize/reparse step to occur twice. Removing `__rust_force_expr` greatly reduces the extra overhead for the `deep-vector` benchmark.r? ```@oli-obk```
2 parentsb1f4397 +9828e96 commitd3debc0

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3 files changed

+10
-17
lines changed

3 files changed

+10
-17
lines changed

‎library/alloc/src/macros.rs‎

Lines changed: 4 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -41,18 +41,18 @@
4141
#[allow_internal_unstable(rustc_attrs, liballoc_internals)]
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macro_rules! vec{
4343
() =>(
44-
$crate::__rust_force_expr!($crate::vec::Vec::new())
44+
$crate::vec::Vec::new()
4545
);
4646
($elem:expr; $n:expr) =>(
47-
$crate::__rust_force_expr!($crate::vec::from_elem($elem, $n))
47+
$crate::vec::from_elem($elem, $n)
4848
);
4949
($($x:expr),+ $(,)?) =>(
50-
$crate::__rust_force_expr!(<[_]>::into_vec(
50+
<[_]>::into_vec(
5151
// This rustc_box is not required, but it produces a dramatic improvement in compile
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// time when constructing arrays with many elements.
5353
#[rustc_box]
5454
$crate::boxed::Box::new([$($x),+])
55-
))
55+
)
5656
);
5757
}
5858

@@ -126,13 +126,3 @@ macro_rules! format {
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res
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}}
128128
}
129-
130-
/// Force AST node to an expression to improve diagnostics in pattern position.
131-
#[doc(hidden)]
132-
#[macro_export]
133-
#[unstable(feature ="liballoc_internals", issue ="none", reason ="implementation detail")]
134-
macro_rules! __rust_force_expr{
135-
($e:expr) =>{
136-
$e
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};
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}

‎tests/ui/macros/vec-macro-in-pattern.rs‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@
44

55
fnmain(){
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matchSome(vec![42]){
7-
Some(vec![43]) =>{}//~ ERRORarbitrary expressions aren't allowed in patterns
7+
Some(vec![43]) =>{}//~ ERRORexpected pattern, found `#`
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_ =>{}
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}
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}

‎tests/ui/macros/vec-macro-in-pattern.stderr‎

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,10 +1,13 @@
1-
error:arbitrary expressions aren't allowed in patterns
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error:expected pattern, found `#`
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--> $DIR/vec-macro-in-pattern.rs:7:14
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|
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LL | Some(vec![43]) => {}
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| ^^^^^^^^
6+
| |
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| expected pattern
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| in this macro invocation
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| this macro call doesn't expand to a pattern
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|
7-
= note: the `expr` fragment specifier forces the metavariable's content to be an expression
811
= note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
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1013
error: aborting due to 1 previous error

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