user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Rollup merge of #57175 - oli-obk:const_let_stabilization, r=nikomatsakis

Browse source 
Stabilize `let` bindings and destructuring in constants and const fn

r? @Centril

This PR stabilizes the following features in constants and `const` functions:

* irrefutable destructuring patterns (e.g. `const fn foo((x, y): (u8, u8)) { ... }`)
* `let` bindings (e.g. `let x = 1;`)
* mutable `let` bindings (e.g. `let mut x = 1;`)
* assignment (e.g. `x = y`) and assignment operator (e.g. `x += y`) expressions, even where the assignment target is a projection (e.g. a struct field or index operation like `x[3] = 42`)
* expression statements (e.g. `3;`)

This PR does explicitly *not* stabilize:

* mutable references (i.e. `&mut T`)
* dereferencing mutable references
* refutable patterns (e.g. `Some(x)`)
* operations on `UnsafeCell` types (as that would need raw pointers and mutable references and such, not because it is explicitly forbidden. We can't explicitly forbid it as such values are OK as long as they aren't mutated.)
* We are not stabilizing `let` bindings in constants that use `&&` and `||` short circuiting operations. These are treated as `&` and `|` inside `const` and `static` items right now. If we stopped treating them as `&` and `|` after stabilizing `let` bindings, we'd break code like `let mut x = false; false && { x = true; false };`. So to use `let` bindings in constants you need to change `&&` and `||` to `&` and `|` respectively.
This commit is contained in:
Mazdak Farrokhzad 2019-01-12 10:54:56 +01:00 • committed by GitHub
commit bd8f464877
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
94 changed files with 416 additions and 977 deletions
Download patch file Download diff file Expand all files Collapse all files

60
src/test/ui/issues/issue-18118.nll.stderr
View file

@ -1,68 +1,14 @@
error[E0658]: let bindings in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:5:17
|
LL | let p = 3;
| ^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: statements in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:5:17
|
LL | let p = 3;
| ^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: let bindings in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:8:9
|
LL | &p //~ ERROR `p` does not live long enough
| ^^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: let bindings in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:2:5
|
LL | / const z: &'static isize = {
LL | | //~^ ERROR let bindings in constants are unstable
LL | | //~| ERROR statements in constants are unstable
LL | | let p = 3;
... |
LL | | //~^ ERROR let bindings in constants are unstable
LL | | };
| |______^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: statements in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:2:5
|
LL | / const z: &'static isize = {
LL | | //~^ ERROR let bindings in constants are unstable
LL | | //~| ERROR statements in constants are unstable
LL | | let p = 3;
... |
LL | | //~^ ERROR let bindings in constants are unstable
LL | | };
| |______^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0597]: `p` does not live long enough
--> $DIR/issue-18118.rs:8:9
--> $DIR/issue-18118.rs:4:9
|
LL | &p //~ ERROR `p` does not live long enough
| ^^
| |
| borrowed value does not live long enough
| using this value as a constant requires that `p` is borrowed for `'static`
LL | //~^ ERROR let bindings in constants are unstable
LL | };
| - `p` dropped here while still borrowed
error: aborting due to 6 previous errors
error: aborting due to previous error
Some errors occurred: E0597, E0658.
For more information about an error, try `rustc --explain E0597`.
For more information about this error, try `rustc --explain E0597`.

5
src/test/ui/issues/issue-18118.rs
View file

@ -1,11 +1,6 @@
pub fn main() {
const z: &'static isize = {
//~^ ERROR let bindings in constants are unstable
//~| ERROR statements in constants are unstable
let p = 3;
//~^ ERROR let bindings in constants are unstable
//~| ERROR statements in constants are unstable
&p //~ ERROR `p` does not live long enough
//~^ ERROR let bindings in constants are unstable
};
}

60
src/test/ui/issues/issue-18118.stderr
View file

@ -1,67 +1,13 @@
error[E0658]: let bindings in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:5:17
|
LL | let p = 3;
| ^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: statements in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:5:17
|
LL | let p = 3;
| ^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: let bindings in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:8:9
|
LL | &p //~ ERROR `p` does not live long enough
| ^^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: let bindings in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:2:5
|
LL | / const z: &'static isize = {
LL | | //~^ ERROR let bindings in constants are unstable
LL | | //~| ERROR statements in constants are unstable
LL | | let p = 3;
... |
LL | | //~^ ERROR let bindings in constants are unstable
LL | | };
| |______^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: statements in constants are unstable (see issue #48821)
--> $DIR/issue-18118.rs:2:5
|
LL | / const z: &'static isize = {
LL | | //~^ ERROR let bindings in constants are unstable
LL | | //~| ERROR statements in constants are unstable
LL | | let p = 3;
... |
LL | | //~^ ERROR let bindings in constants are unstable
LL | | };
| |______^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0597]: `p` does not live long enough
--> $DIR/issue-18118.rs:8:10
--> $DIR/issue-18118.rs:4:10
|
LL | &p //~ ERROR `p` does not live long enough
| ^ borrowed value does not live long enough
LL | //~^ ERROR let bindings in constants are unstable
LL | };
| - borrowed value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error: aborting due to 6 previous errors
error: aborting due to previous error
Some errors occurred: E0597, E0658.
For more information about an error, try `rustc --explain E0597`.
For more information about this error, try `rustc --explain E0597`.

15
src/test/ui/issues/issue-32829-2.rs
View file

@ -1,11 +1,8 @@
// ignore-tidy-linelength
#![feature(const_fn)]
const bad : u32 = {
{
5;
//~^ ERROR statements in constants are unstable
0
}
};
@ -13,8 +10,7 @@ const bad : u32 = {
const bad_two : u32 = {
{
invalid();
//~^ ERROR statements in constants are unstable
//~^^ ERROR: calls in constants are limited to constant functions, tuple structs and tuple variants
//~^ ERROR: calls in constants are limited to constant functions, tuple structs and tuple variants
0
}
};
@ -22,7 +18,6 @@ const bad_two : u32 = {
const bad_three : u32 = {
{
valid();
//~^ ERROR statements in constants are unstable
0
}
};
@ -30,7 +25,6 @@ const bad_three : u32 = {
static bad_four : u32 = {
{
5;
//~^ ERROR statements in statics are unstable
0
}
};
@ -39,7 +33,6 @@ static bad_five : u32 = {
{
invalid();
//~^ ERROR: calls in statics are limited to constant functions, tuple structs and tuple variants
//~| ERROR statements in statics are unstable
0
}
};
@ -47,7 +40,6 @@ static bad_five : u32 = {
static bad_six : u32 = {
{
valid();
//~^ ERROR statements in statics are unstable
0
}
};
@ -55,7 +47,6 @@ static bad_six : u32 = {
static mut bad_seven : u32 = {
{
5;
//~^ ERROR statements in statics are unstable
0
}
};
@ -63,8 +54,7 @@ static mut bad_seven : u32 = {
static mut bad_eight : u32 = {
{
invalid();
//~^ ERROR statements in statics are unstable
//~| ERROR: calls in statics are limited to constant functions, tuple structs and tuple variants
//~^ ERROR: calls in statics are limited to constant functions, tuple structs and tuple variants
0
}
};
@ -72,7 +62,6 @@ static mut bad_eight : u32 = {
static mut bad_nine : u32 = {
{
valid();
//~^ ERROR statements in statics are unstable
0
}
};

83
src/test/ui/issues/issue-32829-2.stderr
View file

@ -1,94 +1,21 @@
error[E0658]: statements in constants are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:7:9
|
LL | 5;
| ^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0015]: calls in constants are limited to constant functions, tuple structs and tuple variants
--> $DIR/issue-32829-2.rs:15:9
--> $DIR/issue-32829-2.rs:12:9
|
LL | invalid();
| ^^^^^^^^^
error[E0658]: statements in constants are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:15:9
|
LL | invalid();
| ^^^^^^^^^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: statements in constants are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:24:9
|
LL | valid();
| ^^^^^^^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: statements in statics are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:32:9
|
LL | 5;
| ^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0015]: calls in statics are limited to constant functions, tuple structs and tuple variants
--> $DIR/issue-32829-2.rs:40:9
--> $DIR/issue-32829-2.rs:34:9
|
LL | invalid();
| ^^^^^^^^^
error[E0658]: statements in statics are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:40:9
|
LL | invalid();
| ^^^^^^^^^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: statements in statics are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:49:9
|
LL | valid();
| ^^^^^^^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0658]: statements in statics are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:57:9
|
LL | 5;
| ^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error[E0015]: calls in statics are limited to constant functions, tuple structs and tuple variants
--> $DIR/issue-32829-2.rs:65:9
--> $DIR/issue-32829-2.rs:56:9
|
LL | invalid();
| ^^^^^^^^^
error[E0658]: statements in statics are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:65:9
|
LL | invalid();
| ^^^^^^^^^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error: aborting due to 3 previous errors
error[E0658]: statements in statics are unstable (see issue #48821)
--> $DIR/issue-32829-2.rs:74:9
|
LL | valid();
| ^^^^^^^
|
= help: add #![feature(const_let)] to the crate attributes to enable
error: aborting due to 12 previous errors
Some errors occurred: E0015, E0658.
For more information about an error, try `rustc --explain E0015`.
For more information about this error, try `rustc --explain E0015`.

4
src/test/ui/issues/issue-37550.rs
View file

@ -1,6 +1,6 @@
const fn x() {
let t = true; //~ ERROR local variables in const fn
let x = || t;
let t = true;
let x = || t; //~ ERROR function pointers in const fn are unstable
}
fn main() {}

6
src/test/ui/issues/issue-37550.stderr
View file

@ -1,7 +1,7 @@
error: local variables in const fn are unstable
--> $DIR/issue-37550.rs:2:9
error: function pointers in const fn are unstable
--> $DIR/issue-37550.rs:3:9
|
LL | let t = true; //~ ERROR local variables in const fn
LL | let x = || t; //~ ERROR function pointers in const fn are unstable
| ^
error: aborting due to previous error

1
src/test/ui/issues/issue-7364.rs
View file

@ -6,5 +6,6 @@ use std::cell::RefCell;
static boxed: Box<RefCell<isize>> = box RefCell::new(0);
//~^ ERROR allocations are not allowed in statics
//~| ERROR `std::cell::RefCell<isize>` cannot be shared between threads safely [E0277]
//~| ERROR static contains unimplemented expression type
fn main() { }

10
src/test/ui/issues/issue-7364.stderr
View file

@ -4,6 +4,12 @@ error[E0010]: allocations are not allowed in statics
LL | static boxed: Box<RefCell<isize>> = box RefCell::new(0);
| ^^^^^^^^^^^^^^^^^^^ allocation not allowed in statics
error[E0019]: static contains unimplemented expression type
--> $DIR/issue-7364.rs:6:41
|
LL | static boxed: Box<RefCell<isize>> = box RefCell::new(0);
| ^^^^^^^^^^^^^^^
error[E0277]: `std::cell::RefCell<isize>` cannot be shared between threads safely
--> $DIR/issue-7364.rs:6:1
|
@ -15,7 +21,7 @@ LL | static boxed: Box<RefCell<isize>> = box RefCell::new(0);
= note: required because it appears within the type `std::boxed::Box<std::cell::RefCell<isize>>`
= note: shared static variables must have a type that implements `Sync`
error: aborting due to 2 previous errors
error: aborting due to 3 previous errors
Some errors occurred: E0010, E0277.
Some errors occurred: E0010, E0019, E0277.
For more information about an error, try `rustc --explain E0010`.