Avoid showing this error where it doesn't make sense by not assuming
"and" and "or" were intended to mean "&&" and "||" until after we decide
to continue parsing input as an associative expression.

Note that the decision of whether or not to continue parsing input as an
associative expression doesn't actually depend on this assumption.

Fixes #75599

It has been deny_by_default since 2017 (and warned for some time
before that), so it seems reasonable to promote it.

The specific technical motivation to do this now is to remove a field
from `ParseSess` -- it is a global state, and global state makes
extracting libraries annoying.

Closes #40107

This commit modifies polymorphization's handling of predicates so that
if any generic parameter is used in a predicate then all parameters in
that predicate are used.
Signed-off-by: NDavid Wood <david@davidtw.co>

Change `UnsafetyViolationKind::General` to `UnsafetyViolationKind::GeneralAndConstFn` in check_unsafety.rs

Remove unsafe in min_const_fn_unsafe_bad.rs

Bless min_const_fn

Add the test case from issue 75340
Co-authored-by: Nlzutao <taolzu@gmail.com>

When a user tries to use a method as if it returned a new value of the
same type as its receiver, we will emit a type error. Try to detect this
and provide extra explanation that the method modifies the receiver
in-place.

This has confused people in the wild, like in
https://users.rust-lang.org/t/newbie-why-the-commented-line-stops-the-snippet-from-compiling/47322

Implement 'considered equal' for statements, so that for example `_0 = _1` and `discriminant(_0) = discriminant(0)` are considered equal if 0 is a fieldless variant of an enum

This commit simplifies `is_range_literal` by checking for
`QPath::LangItem` containing range-related lang items, rather than using
a heuristic.
Co-authored-by: NMatthew Jasper <mjjasper1@gmail.com>
Signed-off-by: NDavid Wood <david@davidtw.co>

This commit introduces `QPath::LangItem` to the HIR and uses it in AST
lowering instead of constructing a `hir::Path` from a slice of symbols.

This might be better for performance, but is also much cleaner as the
previous approach is fragile. In addition, it resolves a bug (#61019)
where an extern crate imported as "std" would result in the paths
created during AST lowering being resolved incorrectly (or not at all).
Co-authored-by: NMatthew Jasper <mjjasper1@gmail.com>
Signed-off-by: NDavid Wood <david@davidtw.co>

This commit adds a test for #61019 where a extern crate is imported as
`std` which results in name resolution to fail due to the uses of `std`
types introduced from lowering.
Signed-off-by: NDavid Wood <david@davidtw.co>

The match branch simplification is applied when target blocks contain
statements that are either equal or perform a const bool assignment with
different values to the same place.

Previously, when constructing new statements, only statements from a
single block had been examined. This lead to a misoptimization when
statements are equal because the assign the *same* const bool value to
the same place.

Fix the issue by examining statements from both blocks when deciding on
replacement.

This commit adjusts polymorphization's handling of predicates so that
after ensuring that `T` is used in `I: Foo<T>` if `I` is used, it now
ensures that `I` is used if `T` is used in `I: Foo<T>`. This is
necessary to mark generic parameters that only exist in impl parameters
as used - thereby avoiding symbol clashes when using the new mangling
scheme.
Signed-off-by: NDavid Wood <david@davidtw.co>

It might be necessary to use its value more than once.

When encountering multiple non-auto trait bounds suggest creating a new
trait and explain what auto-traits are.

I found some areas for improvement while attempting to debug the
SegFault issue when running rust programs compiled using MSVC, with
coverage instrumentation.

I discovered that LLVM's coverage writer was generating incomplete
function name variable names (that's not a typo: the name of the
variable that holds a function name).

The existing implementation used one-up numbers to distinguish
variables, and correcting the names did not fix the MSVC coverage bug,
but the fix in this PR makes the names and resulting LLVM IR easier to
follow and more consistent with Clang's implementation.

I also changed the way the `-Zinstrument-coverage` option is supported
in symbol_export.rs. The original implementation was incorrect, and the
corrected version matches the handling for `-Zprofile-generate`, as it
turns out.

(An argument could be made that maybe `-Zinstrument-coverage` should
automatically enable `-Cprofile-generate`. In fact, if
`-Cprofile-generate` is analagous to Clang's `-fprofile-generate`, as
some documentation implies, Clang always requires this flag for its
implementation of source-based code coverage. This would require a
little more validation, and if implemented, would probably require
updating some of the user-facing messages related to
`-Cprofile-generate` to not be so specific to the PGO use case.)

None of these changes fixed the MSVC coverage problems, but they should
still be welcome improvements.

Lastly, I added some additional FIXME comments in instrument_coverage.rs
describing issues I found with the generated LLVM IR that would be
resolved if the coverage instrumentation is injected with a `Statement`
instead of as a new `BasicBlock`. I describe seven advantages of this
change, but it requires some discussion before making a change like
this.

Emit E0288 (lifetime bound for trait object cannot be deduced) only on
bare trait objects. When the trait object is in the form of
`&dyn Trait`, E0106 (missing lifetime specifier) will have been emitted,
making the former redundant.

This also explicitly checks that the types are `bool`. `try_eval_bool` also appears to just
succeed for `u8`, so this ensures that it actually is a bool before casting.