lcnr
647052fc04
remove the Subst trait, always use EarlyBinder
2022-09-19 11:37:27 +02:00
Dylan DPC
3ad81e0dd8
Rollup merge of #93628 - est31:stabilize_let_else, r=joshtriplett
...
Stabilize `let else`
🎉 **Stabilizes the `let else` feature, added by [RFC 3137](https://github.com/rust-lang/rfcs/pull/3137 ).** 🎉
Reference PR: https://github.com/rust-lang/reference/pull/1156
closes #87335 (`let else` tracking issue)
FCP: https://github.com/rust-lang/rust/pull/93628#issuecomment-1029383585
----------
## Stabilization report
### Summary
The feature allows refutable patterns in `let` statements if the expression is
followed by a diverging `else`:
```Rust
fn get_count_item(s: &str) -> (u64, &str) {
let mut it = s.split(' ');
let (Some(count_str), Some(item)) = (it.next(), it.next()) else {
panic!("Can't segment count item pair: '{s}'");
};
let Ok(count) = u64::from_str(count_str) else {
panic!("Can't parse integer: '{count_str}'");
};
(count, item)
}
assert_eq!(get_count_item("3 chairs"), (3, "chairs"));
```
### Differences from the RFC / Desugaring
Outside of desugaring I'm not aware of any differences between the implementation and the RFC. The chosen desugaring has been changed from the RFC's [original](https://rust-lang.github.io/rfcs/3137-let-else.html#reference-level-explanations ). You can read a detailed discussion of the implementation history of it in `@cormacrelf` 's [summary](https://github.com/rust-lang/rust/pull/93628#issuecomment-1041143670 ) in this thread, as well as the [followup](https://github.com/rust-lang/rust/pull/93628#issuecomment-1046598419 ). Since that followup, further changes have happened to the desugaring, in #98574 , #99518 , #99954 . The later changes were mostly about the drop order: On match, temporaries drop in the same order as they would for a `let` declaration. On mismatch, temporaries drop before the `else` block.
### Test cases
In chronological order as they were merged.
Added by df9a2e0687#87688 ):
* [`ui/pattern/usefulness/top-level-alternation.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/pattern/usefulness/top-level-alternation.rs ) to ensure the unreachable pattern lint visits patterns inside `let else`.
Added by 5b95df4bdc#87688 ):
* [`ui/let-else/let-else-bool-binop-init.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-bool-binop-init.rs ) to ensure that no lazy boolean expressions (using `&&` or `||`) are allowed in the expression, as the RFC mandates.
* [`ui/let-else/let-else-brace-before-else.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-brace-before-else.rs ) to ensure that no `}` directly preceding the `else` is allowed in the expression, as the RFC mandates.
* [`ui/let-else/let-else-check.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-check.rs ) to ensure that `#[allow(...)]` attributes added to the entire `let` statement apply for the `else` block.
* [`ui/let-else/let-else-irrefutable.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-irrefutable.rs ) to ensure that the `irrefutable_let_patterns` lint fires.
* [`ui/let-else/let-else-missing-semicolon.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-missing-semicolon.rs ) to ensure the presence of semicolons at the end of the `let` statement.
* [`ui/let-else/let-else-non-diverging.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-non-diverging.rs ) to ensure the `else` block diverges.
* [`ui/let-else/let-else-run-pass.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-run-pass.rs ) to ensure the feature works in some simple test case settings.
* [`ui/let-else/let-else-scope.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-scope.rs ) to ensure the bindings created by the outer `let` expression are not available in the `else` block of it.
Added by bf7c32a447#89965 ):
* [`ui/let-else/issue-89960.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/issue-89960.rs ) as a regression test for the ICE-on-error bug #89960 . Later in 102b9125e1856541963c#89974 ):
* [`ui/let-else/let-else-if.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-if.rs ) to test for the improved error message that points out that `let else if` is not possible.
Added by 9b45713b6chttps://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-allow-unused.rs ) as a regression test for #89807 , to ensure that `#[allow(...)]` attributes added to the entire `let` statement apply for bindings created by the `let else` pattern.
Added by 61bcd8d307#89841 ):
* [`ui/let-else/let-else-non-copy.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-non-copy.rs ) to ensure that a copy is performed out of non-copy wrapper types. This mirrors `if let` behaviour. The test case bases on rustc internal changes originally meant for #89933 but then removed from the PR due to the error prior to the improvements of #89841 .
* [`ui/let-else/let-else-source-expr-nomove-pass.rs `](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-source-expr-nomove-pass.rs ) to ensure that while there is a move of the binding in the successful case, the `else` case can still access the non-matching value. This mirrors `if let` behaviour.
Added by 102b9125e1#89841 ):
* [`ui/let-else/let-else-ref-bindings.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-ref-bindings.rs ) and [`ui/let-else/let-else-ref-bindings-pass.rs `](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-ref-bindings-pass.rs ) to check `ref` and `ref mut` keywords in the pattern work correctly and error when needed.
Added by 2715c5f984#89841 ):
* Match ergonomic tests adapted from the `rfc2005` test suite.
Added by fec8a507a2#89841 ):
* [`ui/let-else/let-else-deref-coercion-annotated.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-deref-coercion-annotated.rs ) and [`ui/let-else/let-else-deref-coercion.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-deref-coercion.rs ) to check deref coercions.
#### Added since this stabilization report was originally written (2022-02-09)
Added by 76ea566677#94211 ):
* [`ui/let-else/let-else-destructuring.rs`](https://github.com/rust-lang/rust/blob/1.63.0/src/test/ui/let-else/let-else-destructuring.rs ) to give a nice error message if an user tries to do an assignment with a (possibly refutable) pattern and an `else` block, like asked for in #93995 .
Added by e7730dcb7e#94208 ):
* [`ui/let-else/let-else-allow-in-expr.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-allow-in-expr.rs ) to test whether `#[allow(unused_variables)]` works in the expr, as well as its non presence, as well as putting it on the entire `let else` *affects* the expr, too. This was adding a missing test as pointed out by the stabilization report.
* Expansion of `ui/let-else/let-else-allow-unused.rs` and `ui/let-else/let-else-check.rs` to ensure that non-presence of `#[allow(unused)]` does issue the unused lint. This was adding a missing test case as pointed out by the stabilization report.
Added by 5bd71063b3#94208 ):
* [`ui/let-else/let-else-slicing-error.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-slicing-error.rs ), a regression test for #92069 , which got fixed without addition of a regression test. This resolves a missing test as pointed out by the stabilization report.
Added by 5374688e1d#98574 ):
* [`src/test/ui/async-await/async-await-let-else.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/async-await/async-await-let-else.rs ) to test the interaction of async/await with `let else`
Added by 6c529ded86#98574 ):
* [`src/test/ui/let-else/let-else-temporary-lifetime.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-temporary-lifetime.rs ) as a (partial) regression test for #98672
Added by 9b56640106#99518 ):
* [`src/test/ui/let-else/let-else-temp-borrowck.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-temporary-lifetime.rs ) as a regression test for #93951
* Extension of `src/test/ui/let-else/let-else-temporary-lifetime.rs` to include a partial regression test for #98672 (especially regarding `else` drop order)
Added by baf9a7cb57#99518 ):
* Extension of `src/test/ui/let-else/let-else-temporary-lifetime.rs` to include a partial regression test for #93951 , similar to `let-else-temp-borrowck.rs`
Added by 60be2de8b7#99518 ):
* Extension of `src/test/ui/let-else/let-else-temporary-lifetime.rs` to include a program that can now be compiled thanks to borrow checker implications of #99518
Added by 47a7a91c96#100132 ):
* [`src/test/ui/let-else/issue-100103.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/issue-100103.rs ), as a regression test for #100103 , to ensure that there is no ICE when doing `Err(...)?` inside else blocks.
Added by e3c5bd617d#100443 ):
* [`src/test/ui/let-else/let-else-then-diverge.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-then-diverge.rs ), to verify that there is no unreachable code error with the current desugaring.
Added by 981852677c#100443 ):
* [`src/test/ui/let-else/issue-94176.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/issue-94176.rs ), to make sure that a correct span is emitted for a missing trailing expression error. Regression test for #94176 .
Added by e182d12a84#100434 ):
* [src/test/ui/unpretty/pretty-let-else.rs](https://github.com/rust-lang/rust/blob/master/src/test/ui/unpretty/pretty-let-else.rs ), as a regression test to ensure pretty printing works for `let else` (this bug surfaced in many different ways)
Added by e26285603c#99954 ):
* [`src/test/ui/let-else/let-else-temporary-lifetime.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-temporary-lifetime.rs ) extended to contain & borrows as well, as this was identified as an earlier issue with the desugaring: https://github.com/rust-lang/rust/issues/98672#issuecomment-1200196921
Added by 2d8460ef43#99291 ):
* [`src/test/ui/let-else/let-else-drop-order.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-drop-order.rs ) a matrix based test for various drop order behaviour of `let else`. Especially, it verifies equality of `let` and `let else` drop orders, [resolving](https://github.com/rust-lang/rust/pull/93628#issuecomment-1238498468 ) a [stabilization blocker](https://github.com/rust-lang/rust/pull/93628#issuecomment-1055738523 ).
Added by 1b87ce0d40#101410 ):
* Edit to `src/test/ui/let-else/let-else-temporary-lifetime.rs` to add the `-Zvalidate-mir` flag, as a regression test for #99228
Added by af591ebe4d#101410 ):
* [`src/test/ui/let-else/issue-99975.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/issue-99975.rs ) as a regression test for the ICE #99975 .
Added by this PR:
* `ui/let-else/let-else.rs`, a simple run-pass check, similar to `ui/let-else/let-else-run-pass.rs`.
### Things not currently tested
* ~~The `#[allow(...)]` tests check whether allow works, but they don't check whether the non-presence of allow causes a lint to fire.~~ → *test added by e7730dcb7eb29a10ee73f269f4dc6e9d606db0da*
* ~~There is no `#[allow(...)]` test for the expression, as there are tests for the pattern and the else block.~~ → *test added by e7730dcb7eb29a10ee73f269f4dc6e9d606db0da*
* ~~`let-else-brace-before-else.rs` forbids the `let ... = {} else {}` pattern and there is a rustfix to obtain `let ... = ({}) else {}`. I'm not sure whether the `.fixed` files are checked by the tooling that they compile. But if there is no such check, it would be neat to make sure that `let ... = ({}) else {}` compiles.~~ → *test added by e7730dcb7eb29a10ee73f269f4dc6e9d606db0da*
* ~~#92069 got closed as fixed, but no regression test was added. Not sure it's worth to add one.~~ → *test added by 5bd71063b3810d977aa376d1e6dd7cec359330cc*
* ~~consistency between `let else` and `if let` regarding lifetimes and drop order: https://github.com/rust-lang/rust/pull/93628#issuecomment-1055738523~~ → *test added by 2d8460ef43d902f34ba2133fe38f66ee8d2fdafc*
Edit: they are all tested now.
### Possible future work / Refutable destructuring assignments
[RFC 2909](https://rust-lang.github.io/rfcs/2909-destructuring-assignment.html ) specifies destructuring assignment, allowing statements like `FooBar { a, b, c } = foo();`.
As it was stabilized, destructuring assignment only allows *irrefutable* patterns, which before the advent of `let else` were the only patterns that `let` supported.
So the combination of `let else` and destructuring assignments gives reason to think about extensions of the destructuring assignments feature that allow refutable patterns, discussed in #93995 .
A naive mapping of `let else` to destructuring assignments in the form of `Some(v) = foo() else { ... };` might not be the ideal way. `let else` needs a diverging `else` clause as it introduces new bindings, while assignments have a default behaviour to fall back to if the pattern does not match, in the form of not performing the assignment. Thus, there is no good case to require divergence, or even an `else` clause at all, beyond the need for having *some* introducer syntax so that it is clear to readers that the assignment is not a given (enums and structs look similar). There are better candidates for introducer syntax however than an empty `else {}` clause, like `maybe` which could be added as a keyword on an edition boundary:
```Rust
let mut v = 0;
maybe Some(v) = foo(&v);
maybe Some(v) = foo(&v) else { bar() };
```
Further design discussion is left to an RFC, or the linked issue.
2022-09-17 15:31:06 +05:30
bors
c524c7dd25
Auto merge of #98588 - b-naber:valtrees-cleanup, r=lcnr
...
Use only ty::Unevaluated<'tcx, ()> in type system
r? `@lcnr`
2022-09-17 03:04:22 +00:00
est31
173eb6f407
Only enable the let_else feature on bootstrap
...
On later stages, the feature is already stable.
Result of running:
rg -l "feature.let_else" compiler/ src/librustdoc/ library/ | xargs sed -s -i "s#\\[feature.let_else#\\[cfg_attr\\(bootstrap, feature\\(let_else\\)#"
2022-09-15 21:06:45 +02:00
b-naber
29c0364c37
rebase
2022-09-13 17:48:05 +02:00
Eric Holk
6c01273a15
Plumb dyn trait representation through ty::Dynamic
2022-09-12 16:55:55 -07:00
bors
3194958217
Auto merge of #100251 - compiler-errors:tuple-trait-2, r=jackh726
...
Implement `std::marker::Tuple`
Split out from #99943 (https://github.com/rust-lang/rust/pull/99943#pullrequestreview-1064459183 ).
Implements part of rust-lang/compiler-team#537
r? `@jackh726`
2022-09-12 03:24:29 +00:00
Andrew Cann
22f4bbb20f
Apply formatting fixes
2022-09-11 14:04:16 +08:00
Andrew Cann
2c0bc9444e
implement Copy/Clone for generators
2022-09-11 13:50:35 +08:00
lcnr
c63020a7c3
rename codegen_fulfill_obligation
2022-09-09 13:36:27 +02:00
lcnr
14f2acd0ac
resolve_instance: remove BoundVarsCollector
2022-09-09 13:08:07 +02:00
Michael Goulet
78b962a4f3
RPITIT placeholder items
2022-09-09 01:31:44 +00:00
Nicholas Nethercote
2c4c8eb1a3
Box PatKind::Range.
...
Because it's the biggest variant. Also, make `PatRange` non-`Copy`,
because it's 104 bytes, which is pretty big.
2022-09-02 07:26:22 +10:00
Nicholas Nethercote
053874eecc
Clean up THIR patterns.
...
`thir::Pat::kind` is a `Box<PatKind>`, which doesn't follow the usual
pattern in AST/HIR/THIR which is that the "kind" enum for a node is
stored inline within the parent struct.
This commit makes the `PatKind` directly inline within the `Pat`. This
requires using `Box<Pat>` in all the types that hold a `Pat.
Ideally, `Pat` would be stored in `Thir` like `Expr` and `Stmt` and
referred to with a `PatId` rather than `Box<Pat>`. But this is hard to
do because lots of `Pat`s get created after the destruction of the `Cx`
that does normal THIR building. But this does get us a step closer to
`PatId`, because all the `Box<Pat>` occurrences would be replaced with
`PatId` if `PatId` ever happened.
At 128 bytes, `Pat` is large. Subsequent commits will shrink it.
2022-09-02 07:26:17 +10:00
Oli Scherer
1fc9ef1edd
tracing::instrument cleanup
2022-09-01 14:54:27 +00:00
Oli Scherer
ee3c835018
Always import all tracing macros for the entire crate instead of piecemeal by module
2022-09-01 14:54:27 +00:00
Matthias Krüger
d182081de1
Rollup merge of #99027 - tmiasko:basic-blocks, r=oli-obk
...
Replace `Body::basic_blocks()` with field access
Since the refactoring in #98930 , it is possible to borrow the basic blocks
independently from other parts of MIR by accessing the `basic_blocks` field
directly.
Replace unnecessary `Body::basic_blocks()` method with a direct field access,
which has an additional benefit of borrowing the basic blocks only.
2022-08-29 06:34:43 +02:00
Peter Medus
01c1616b25
Migrate rustc_ty_utils to use SessionDiagnostic
2022-08-26 14:36:51 +01:00
Tomasz Miąsko
b48870b451
Replace Body::basic_blocks() with field access
2022-08-26 14:27:08 +02:00
Nicholas Nethercote
2df805fc7a
Store blocks in Thir.
...
Like expressions, statements, and match arms. This shrinks `thir::Stmt`
and is a precursor to further shrinking `thir::Expr`.
2022-08-24 15:06:44 +10:00
lcnr
4fe666ee64
implied_bounds: clarify our assumptions
2022-08-17 12:22:32 +02:00
Michael Goulet
d0e4c679ff
Built-in implementation of Tuple trait
2022-08-07 16:31:03 -07:00
Jack Huey
955fcad758
Add bound_impl_subject and bound_return_ty
2022-08-03 01:02:46 -04:00
Jack Huey
96a69dce2c
Change sized_constraints to return EarlyBinder
2022-08-03 00:14:24 -04:00
Camille GILLOT
957548183d
Remove trait_of_item query.
2022-08-01 21:39:26 +02:00
Camille GILLOT
d7ea161b7e
Remove DefId from AssocItemContainer.
2022-08-01 21:38:45 +02:00
Camille GILLOT
8ee4446ee5
Remove visibility from AssocItem.
2022-08-01 21:38:20 +02:00
Camille GILLOT
110f0656cb
Store associated item defaultness in impl_defaultness.
2022-08-01 21:38:16 +02:00
Miguel Guarniz
16513d689e
Rename local_did to def_id
...
Signed-off-by: Miguel Guarniz <mi9uel9@gmail.com>
2022-07-29 18:26:10 -04:00
Miguel Guarniz
25bdc8965e
Change maybe_body_owned_by to take local def id
...
Signed-off-by: Miguel Guarniz <mi9uel9@gmail.com>
2022-07-29 18:25:58 -04:00
Michael Goulet
22b2aae737
Do not resolve associated const when there is no provided value
2022-07-22 18:58:07 +00:00
Michael Woerister
88f6c6d8a0
Remove unused StableMap and StableSet types from rustc_data_structures
2022-07-20 13:11:39 +02:00
Dylan DPC
ecae3d74e2
Rollup merge of #99000 - JulianKnodt:allow_resolve_no_substs, r=lcnr
...
Move abstract const to middle
Moves AbstractConst (and all associated methods) to rustc middle for use in `rustc_infer`.
This allows for const resolution in infer to use abstract consts to walk consts and check if
they are resolvable.
This attempts to resolve the issue where `Foo<{ concrete const }, generic T>` is incorrectly marked as conflicting, and is independent from the other issue where nested abstract consts must be resolved.
r? `@lcnr`
2022-07-14 19:24:04 +05:30
kadmin
20fb8aba8f
Fix overlapping impls
2022-07-14 09:01:17 +00:00
Joshua Nelson
3c9765cff1
Rename debugging_opts to unstable_opts
...
This is no longer used only for debugging options (e.g. `-Zoutput-width`, `-Zallow-features`).
Rename it to be more clear.
2022-07-13 17:47:06 -05:00
kadmin
e612e2603c
Move abstract const to rustc_middle::ty
2022-07-12 02:21:31 +00:00
Alan Egerton
4f0a64736b
Update TypeVisitor paths
2022-07-06 06:41:53 +01:00
Alan Egerton
e9e5d0685b
Relax constrained generics to TypeVisitable
2022-07-05 22:25:43 +01:00
lcnr
24799e3720
remove an unused DefId
2022-07-04 14:35:19 +02:00
Camille GILLOT
0161ecd13f
Recover when failing to normalize closure signature.
2022-06-30 21:45:29 +02:00
Dominik Stolz
d048b15216
Improve doc comment of destructure_const
2022-06-29 10:30:47 +02:00
Dominik Stolz
053f48d91f
Address code review comments
2022-06-28 23:26:54 +02:00
Dominik Stolz
080525229b
Make consts mod private
2022-06-28 22:45:05 +02:00
Dominik Stolz
cd88bb332c
Improve pretty printing of valtrees for references
2022-06-28 22:38:32 +02:00
b-naber
705d818bd5
implement valtrees as the type-system representation for constant values
2022-06-14 16:07:11 +02:00
bors
99930ac7f8
Auto merge of #95880 - cjgillot:def-ident-span, r=petrochenkov
...
Handle `def_ident_span` like `def_span`.
`def_ident_span` had an ad-hoc status in the compiler.
This PR refactors it to be a first-class citizen like `def_span`:
- it gets encoded in the main metadata loop, instead of the visitor;
- its implementation is updated to mirror the one of `def_span`.
We do not remove the `Option` in the return type, since some items do not have an ident, AnonConsts for instance.
2022-06-11 20:08:48 +00:00
Camille GILLOT
16f9f7c7b1
Implement def_ident_span in rustc_middle.
2022-06-10 20:15:14 +02:00
bors
e45d9973b2
Auto merge of #97860 - Dylan-DPC:rollup-t3vxos8, r=Dylan-DPC
...
Rollup of 5 pull requests
Successful merges:
- #97595 (Remove unwrap from get_vtable)
- #97597 (Preserve unused pointer to address casts)
- #97819 (Recover `import` instead of `use` in item)
- #97823 (Recover missing comma after match arm)
- #97851 (Use repr(C) when depending on struct layout in ptr tests)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
2022-06-08 08:05:47 +00:00
Dylan DPC
148a44a001
Rollup merge of #97595 - ouz-a:issue-97381, r=compiler-errors
...
Remove unwrap from get_vtable
This avoids ICE on issue #97381 I think the bug is a bit deeper though, it compiles fine when `v` is `&v` which makes me think `Deref` is causing some issue with borrowck but it's fine I guess since this thing crashes since `nightly-2020-09-17` 😅
2022-06-08 07:37:29 +02:00
Nicholas Nethercote
90db033955
Folding revamp.
...
This commit makes type folding more like the way chalk does it.
Currently, `TypeFoldable` has `fold_with` and `super_fold_with` methods.
- `fold_with` is the standard entry point, and defaults to calling
`super_fold_with`.
- `super_fold_with` does the actual work of traversing a type.
- For a few types of interest (`Ty`, `Region`, etc.) `fold_with` instead
calls into a `TypeFolder`, which can then call back into
`super_fold_with`.
With the new approach, `TypeFoldable` has `fold_with` and
`TypeSuperFoldable` has `super_fold_with`.
- `fold_with` is still the standard entry point, *and* it does the
actual work of traversing a type, for all types except types of
interest.
- `super_fold_with` is only implemented for the types of interest.
Benefits of the new model.
- I find it easier to understand. The distinction between types of
interest and other types is clearer, and `super_fold_with` doesn't
exist for most types.
- With the current model is easy to get confused and implement a
`super_fold_with` method that should be left defaulted. (Some of the
precursor commits fixed such cases.)
- With the current model it's easy to call `super_fold_with` within
`TypeFolder` impls where `fold_with` should be called. The new
approach makes this mistake impossible, and this commit fixes a number
of such cases.
- It's potentially faster, because it avoids the `fold_with` ->
`super_fold_with` call in all cases except types of interest. A lot of
the time the compile would inline those away, but not necessarily
always.
2022-06-08 09:24:03 +10:00
