Greetings Rustaceans!
I've just been getting acquainted with Rust through the guide. First let me say that it's already in great shape, chapters are kept a good length to be digestible and paced to move the reader along fluidly, so my compliments to contributors!
Along the way I noticed a few minor copy errors, and also a few areas that I thought more subjectively could stand to be improved. My commits here are divided so that minor edits unlikely to be very contentious could be cherry-picked, and then topically on parts that might generate more discussion.
I also have some comments and questions that aren't directly associated with any changes on this branch yet. I'm not sure how you like to triage this sort of thing but I'll present them below and if it's appropriate they could be moved to separate issues or I might be able to help work some of them out within the scope of this PR. Sorry that these are a lot to take in, pretty much everything below here can be digested independently of the current changes in this PR so you could read the rest later 😄
### Questions and Comments
I'll give stable links to doc revisions as of this writing.
1. The [example using `PartialEq` in the Traits chapter][1] is poor—we have no idea how `PartialEq` works at this point in the text (or at any point, AFAICT), so it isn't clear why it won't work as a trait bound in this situation and `Float` almost magically does, with the aid of existing tailor-made identity functions that seem unlikely to be so conveniently available when we encounter a scenario like this in our real-world code.
This section just seems glossed over, or perhaps content has moved around over time or there's an assumption that implementing equality with `PartialEq` should be covered in the guide eventually so this example will be less foreign. As it stands the text is hard to follow and not very meaningful.
2. I found treatment of the relationship of trait objects to pointers in the *Static and Dynamic Dispatch* chapter unclear. [The "Why Pointers?" section][2] opens with this line:
> The use of language like "fat pointer" implies that a trait object is always a pointer of some form, but why?
But the phrase "fat pointer" hasn't been used anywhere before. This is some of the more complex material in the guide, but this section nevertheless feels displaced, not clearly connecting preceding subject matter. Earlier we've covered the internal representation of trait objects and significance of pointers they contain, but it hasn't been spelled out (other than what `&Foo` syntax suggests) that trait objects are references (and why). That's what the "Why Pointers?" section is aiming to do I gather, but it seems out of place, I think it'd make more sense to cover this before the gory details of their internals.
3. Suggestion: move the *Error Handling* chapter much earlier in the Intermediate section of the guide, or even into the Basics section. I know the Intermediate section isn't intended to be read in order per se, but plenty of people like me are just going to read it straight through anyway 😁 These are pretty fundamental concepts to understand and `Option`, `Result`, and idioms like `unwrap()` and `.ok().expect()` are referenced numerous times throughout the rest of the guide. They feature pretty prominently as early as *Standard Input* and *Guessing Game* chapters in Basics, in fact. I happen to have a good understanding of these already through encountering their analogs in typed functional languages, but if I didn't I believe I really would have appreciated reading *Error Handling* much earlier.
4. In the `rustdoc` chapter, a [comment at the beginning of the first source example][3] refers to a "link" crate attribute being needed. There seems to be no such attribute present in the source. I believe this refers to `crate_type` [according to the reference][4], but it'd be nice if this example were updated/clarified (I think `crate_id` is deprecated/obsolete too).
This brings me to a related comment also: after encountering crate attributes in the reference and also docs on Cargo configuration like `crate-type = ["dylib"]`, I'm uncertain about the relationship/redundancy between these. I'm sure this is the kind of thing where docs are simply struggling to keep pace with rapid changes in Rust and Cargo, just wanted to flag that this distinction ought to be clearly covered in the docs for one or the other at some point, it's presently hard to track down.
5. Minor: link to sample editor configurations in [the introductory chapter][5] is broken, probably the generator automatically translates `.md` links to `.html`. Perhaps it shouldn't do that for absolute URLs.
6. Following from my changes to the enums coverage in [*Compound Data Types*][6] in this PR: sum types are an important topic and I tried to make some improvements, but I think the motivating example of `Character` with `Digit(i32)` and `Other` variants is a pretty weak one, and a better example could greatly improve cohesion with the `Ordering` coverage later in the section and how that ties into pattern matching in the subsequent chapter. I just haven't thought of a better example to suggest yet.
In particular, the text states:
> This may seem rather limiting, but it's a limitation which we can overcome.
This is referring to `Character`, and actually to more than one limitation: the preceding admonition that its variants aren't comparable/don't have ordering, and don't support binary operators like `*` and `+`. Overcoming these limitations actually never gets explained—we next cover how `Ordering` works as an enum itself for plain `i32`s, but never get around to showing how this might be applied to our `Digit` variant type.
Since the coverage of enums already segues into pattern matching and this could be even tighter with a stronger example, it might be nice if our example enum were somehow connected to the final example program for the Basics section too, where `Ordering` reappears. I don't see how it would fit with the current guessing game example, but food for thought.
7. `#[derive]` seems conspicuously missing from the guide. It would probably make sense to introduce after showing simple examples of implementing equality and/or ordering traits by hand, which have been mentioned as possibilities above. Perhaps it's too much to breach this as early as the Basic section though without traits being introduced. `#[derive]` itself and the derivable traits can certainly be saved for Intermediate and referenced as covered later, in any case.
r? @steveklabnik for docs.
[1]: 1576142495/src/doc/trpl/traits.md (our-inverse-example)
[2]: 1576142495/src/doc/trpl/static-and-dynamic-dispatch.md (why-pointers)
[3]: 1576142495/src/doc/trpl/documentation.md (creating-documentation)
[4]: http://doc.rust-lang.org/reference.html#linkage
[5]: 1576142495/src/doc/trpl/hello-world.md
[6]: 1576142495/src/doc/trpl/compound-data-types.md (enums)
Boolean values and small aggregates have a different type in args/allocas than
in SSA values but the intrinsics for volatile and atomic ops were
missing the necessary casts to handle that.
Fixes#23550
This commit removes the `IndexMut` impls on `HashMap` and `BTreeMap`, in
order to future-proof the API against the eventual inclusion of an
`IndexSet` trait.
Ideally, we would eventually be able to support:
```rust
map[owned_key] = val;
map[borrowed_key].mutating_method(arguments);
&mut map[borrowed_key];
```
but to keep the design space as unconstrained as possible, we do not
currently want to support `IndexMut`, in case some other strategy will
eventually be needed.
Code currently using mutating index notation can use `get_mut` instead.
[breaking-change]
Closes#23448
r? @Gankro
After this patch code like `let ref a = *"abcdef"` doesn't cause ICE anymore.
Required for #23121
There are still places in rustc_trans where pointers are always assumed to be thin. In particular, #19064 is not resolved by this patch.
Boolean values and small aggregates have a different type in
args/allocas than in SSA values but the intrinsics for volatile and
atomic ops were missing the necessary casts to handle that.
Fixes#23550
This commit removes the reexports of `old_io` traits as well as `old_path` types
and traits from the prelude. This functionality is now all deprecated and needs
to be removed to make way for other functionality like `Seek` in the `std::io`
module (currently reexported as `NewSeek` in the io prelude).
Closes#23377Closes#23378
This commit removes the reexports of `old_io` traits as well as `old_path` types
and traits from the prelude. This functionality is now all deprecated and needs
to be removed to make way for other functionality like `Seek` in the `std::io`
module (currently reexported as `NewSeek` in the io prelude).
Closes#23377Closes#23378
This reverts commit aec67c2.
Closes#20012
This is temporarily rebased on #23245 as it would otherwise conflict, the last commit is the only one relevant to this PR though.
This commit removes the `IndexMut` impls on `HashMap` and `BTreeMap`, in
order to future-proof the API against the eventual inclusion of an
`IndexSet` trait.
Ideally, we would eventually be able to support:
```rust
map[owned_key] = val;
map[borrowed_key].mutating_method(arguments);
&mut map[borrowed_key];
```
but to keep the design space as unconstrained as possible, we do not
currently want to support `IndexMut`, in case some other strategy will
eventually be needed.
Code currently using mutating index notation can use `get_mut` instead.
[breaking-change]
Closes#23448
When investigating #22518, this chapter is really the only part that has `rand`, and the rest still works without it. We should have some examples like this, but for now, it's more important to be right than perfect.
As @alexcrichton says, this was really a libgreen thing, and isn't
relevant now.
As this removes a technically-public function, this is a
[breaking-change]
`uppercase` and `lowercase` are currently named `to_uppercase` and `to_lowercase`. Also adds a link to the `char` type documentation which has much more detail on these iterators.
These two borrowing examples were confusing/misleading. This changes it
to more clearly show how you _can_ borrow a box, and also uses & instead
of &*.
We don't use 'task' anymore, these are now threads.
Because this changes the name of a compiler option, this is
[breaking-change]
I think this is small enough to not need an RFC, nor a period of accepting both. If we want to take both for a while, I can change the patch.
The IP and socket address types all had `FromStr` implemented but the
implementations were not marked stable, nor was the error type returned ready to
be properly stabilized.
This commit marks the implementations of `FromStr` as stable and also renamed
the `ParseError` structure to `AddrParseError`. The error is now also an opaque
structure that cannot be constructed outside the standard library.
cc #22949
[breaking-change]
The IP and socket address types all had `FromStr` implemented but the
implementations were not marked stable, nor was the error type returned ready to
be properly stabilized.
This commit marks the implementations of `FromStr` as stable and also renamed
the `ParseError` structure to `AddrParseError`. The error is now also an opaque
structure that cannot be constructed outside the standard library.
cc #22949
[breaking-change]
As @alexcrichton says, this was really a libgreen thing, and isn't
relevant now.
As this removes a technically-public function, this is a
[breaking-change]
Conflicts:
src/libtest/lib.rs
