derive: use intrinsics::unreachable over unreachable!()
derive: use intrinsics::unreachable over unreachable!()
Fixes#31574.
Spawned from #32139.
r? @alexcrichton
When deriving Hash, RustcEncodable and RustcDecodable, the syntax extension
needs a type parameter to use in the inner method. They used to use __H, __S
and __D respectively. If this conflicts with a type parameter already declared
for the item, bad times result (see the test). There is no hygiene for type
parameters, but this commit introduces a better heuristic by concatenating the
names of all extant type parameters (and prepending __H).
This changes local variable names in all derives to remove leading
double-underscores. As far as I can tell, this doesn't break anything
because there is no user code in these generated functions except for
struct, field and type parameter names, and this doesn't cause shadowing
of those. But I am still a bit nervous.
This replaces some `if`s with `match`es. This was originally not possible
because using a global path in a match statement caused a "non-constant
path in constant expr" ICE. The issue is long since closed, though you still
hit it (as an error now, not an ICE) if you try to generate match patterns
using pat_lit(expr_path). But it works when constructing the patterns more
carefully.
This commit removes the `-D warnings` flag being passed through the makefiles to
all crates to instead be a crate attribute. We want these attributes always
applied for all our standard builds, and this is more amenable to Cargo-based
builds as well.
Note that all `deny(warnings)` attributes are gated with a `cfg(stage0)`
attribute currently to match the same semantics we have today
This commit removes the `-D warnings` flag being passed through the makefiles to
all crates to instead be a crate attribute. We want these attributes always
applied for all our standard builds, and this is more amenable to Cargo-based
builds as well.
Note that all `deny(warnings)` attributes are gated with a `cfg(stage0)`
attribute currently to match the same semantics we have today
This PR is a rebase of the original PR by @eddyb https://github.com/rust-lang/rust/pull/21836 with some unrebasable parts manually reapplied, feature gate added + type equality restriction added as described below.
This implementation is partial because the type equality restriction is applied to all type ascription expressions and not only those in lvalue contexts. Thus, all difficulties with detection of these contexts and translation of coercions having effect in runtime are avoided.
So, you can't write things with coercions like `let slice = &[1, 2, 3]: &[u8];`. It obviously makes type ascription less useful than it should be, but it's still much more useful than not having type ascription at all.
In particular, things like `let v = something.iter().collect(): Vec<_>;` and `let u = t.into(): U;` work as expected and I'm pretty happy with these improvements alone.
Part of https://github.com/rust-lang/rust/issues/23416
Manish Goregaokar