Sync to upstream/release/694 (#2033)

## What's Changed?

This week we have improvements in new type solver inference, performance
optimizations for the new type solver as well as fixes for optimization
passes in native code generation.

- Fixed the order of errors returned by `Frontend::getCheckResult` with
`accumulateNested` flag
- Typechecker now uses `userdata` instead of `class` as the extern type
name

## New Type Solver
- When a string is passed to a function expecting an argument that might
be a string singleton, bidirectional type inference will choose the
lower bound (string literal) for that argument (Fixes #2010)
- Fixed incorrect definition of `vector.lerp` (Fixes #2024)
- Added error suppression in type path traversal. Without it, errors
with `*error-type*` were sometimes visible (Fixes #1840)
- Fixed another case of combinatorial explosion in union type
normalization which could have caused a hang
- Fixed a crash on out-of-bounds access during `for..in` statement
typechecking

## Runtime
- Fixed an assertion in native code generation in a sequence of `nil`
and `boolean` stores to a local
- Fixed incorrect lowering in rare cases when LuauCodegenDirectCompare
was enabled

## Internal Contributors

Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Annie Tang <annietang@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Ilya Rezvov <irezvov@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

Sync to upstream/release/693 (#2021)

# New Solver
* Avoid bidirectional inference always forcing constraints for simple
code such as the example below. Fixes #2017.
```luau
type Suit = "Hearts" | "Spades" | "Clubs" | "Diamonds"

local getSuits(): { Suit }
    return { "Hearts", "Spades", "Clubs", "Diamonds" }
end
```
* Iterating over an empty pack, such as in the below example, should
error but still allow type inference to complete.
```luau
local function foo() end -- has type `() -> ()`
for _ in foo() do end -- Errors, as you can't iterate over `()`, but type inference still completes.
```
* Implement arity based overload selection: this allows for overloaded
functions with generics to more consistently infer reasonable results.
For example:
```luau
-- This code no longer errors  as we determine that the first overload to 
-- table.insert is what the author intended.
table.insert({} :: { any }, 42)
```
* Allow the`table` type to be a subtype of generic tables. This means
code like the following no longer raises a type error:
```luau
local function doSomething(t: unknown)
    if type(t) == "table" then
        -- Prior we would error as `table` is not a subtype of a generic table
        -- Also works with `pairs` and similar builtin functions.
        local foo, bar = next(t)
    end
end
```
* Descend into intersection types when performing bidirectional
inference, this allows us to correctly bidirectionally infer code like:
```luau
type A = { foo: "a" }
type B = { bar: "b" }
type AB = A & B
-- No longer errors as the literals "a" and "b" will be inferred to be their singleton types.
local t: AB = { foo = "a", bar = "b" }
```
* #2008
* Fix intersections between table types and extern types to preserve
intersections when either type contains an indexer, fixing a regression
introduced when trying to refine table and extern types more precisely:
```luau
function f(obj: { [any]: any }, functionName: string)
    if typeof(obj) == "userdata" then
        -- No longer errors as we still have a `class & { [any]: any }` rather than a `class`
        local _ = obj[functionName]
    end
end
```
* Separated recursion limits for different parts of the new solver. No
immediate changes, but this creates more tools to tamp down on stack
overflows without affecting other subsystems.

# Runtime
* Implement "stackless" `pcall` / `xpcall` in yieldable contexts: this
lets recursive calls to `pcall` nest further, erroring at the Luau call
stack limit (20000 calls as of this writing) rather than the C call
stack limit (200 calls as of this writing)

---

Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

---------

Co-authored-by: Varun Saini <61795485+vrn-sn@users.noreply.github.com>
Co-authored-by: Alexander Youngblood <ayoungblood@roblox.com>
Co-authored-by: Menarul Alam <malam@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>

Sync to origin/release/692 (#2012)

Another week, another release!

## Analysis/Autocomplete

- Improve recursive type lookups by using scoped tracking of processed
types.
- Enforce recursion limits in subtyping on type packs, not just on
types.
- Simplify type checking for intersections between tables and
discriminants containing read-only table properties.
- Allow fields provided by `__index` to satisfy subtyping relationships.
- Improve the ability for the type checker to do proper generic
substitution in `for ... in` loops.
- Fix a fragment autocomplete bug that caused fragments to be selected
incorrectly in `for ... in` loops.
- Fix a crash caused by `typeof` containing an unterminated function
definition: `typeof(function())`.
- Fix a flagging issue that may have been causing stack overflows in the
previous release.

## Runtime

- Support constant folding for interpolated strings.
- Fix a bug caused by the empty string being the result of constant
folding.
- Add helper macros in Bytecode.h to help access data in Luau auxiliary
instruction bits.
- Add support for branchless `==`/`~=` comparisons in CodeGen (in
certain cases).

---

Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Annie Tang <annietang@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Ilya Rezvov <irezvov@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

Sync to upstream/release/691 (#1998)

# New Type Solver
* Fixed #1983 by adding
additional context to permit some expressions otherwise not allowed
* We now skip issuing CheckedFunctionWarnings on use of unreduced type
functions
* Fix gcc compile error
* Handle expressions `a == b` and `a ~= b` more efficiently  
* Subtyping now correctly handles generics over unions and intersections
in cases such as
```
local function a<T>(arr: { T }) end

a({ 'one', 'two' })
```
* Rearrange unification cases to avoid free type generalization to never
* Improve generic bounds mismatch error message
* Fix Ancestry bug in visitor for incomplete repeat blocks such as
```
local t = {}
function t:Foo() end

repeat
  t:|
  ```
*  Support autocomplete for attributes

# Native Codegen
* Unwind info has support on Android
* Introduced a separate ctypeof function which does not constant-fold for vector arguments.
* We now perform string concatenation at compile time if possible (there is a known issue with the optimization that we will address next week)
* Make vector.lerp and math.lerp more efficient with FMA
* Record STORE_SPLIT_TVALUE as a potential restore operation to reduce number of spills to stack 
* When native execution is disabled, we now mark the call frame as not executing natively, making resumption safer

--- 
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Annie Tang <annietang@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Ilya Rezvov <irezvov@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

---------

Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Varun Saini <61795485+vrn-sn@users.noreply.github.com>
Co-authored-by: Alexander Youngblood <ayoungblood@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>

Sync to upstream/release/690 (#1992)

# New Type Solver
* Improve the error message for an uninstantiated type alias, as in:
```luau
type Packed<T...> = (T...) -> T...
local a: Packed -- Now has a single, specific, error
```
* Improve refinements of extern types against table types, ensuring the
extern part is dropped less often, as in:
```luau
local function update(foo: Instance)
    assert(foo.Name == "bubbles")
    -- Previously might have been `{ read Name: "bubbles" }`, 
    -- will now be `Instance & { read Name: "bubbles" }`
    return foo 
end
```
* Resolve an internal complier exception when attempting to use `typeof`
inside the generic type default of an alias. Fixes #1462.
* No longer throw an internal compiler exception for exceptionally large
ASTs, though a `CodeTooComplex` error will still be raised.
* Broadly rework generic pack subtyping to allow code like the following
to type check without errors:
```luau
function f(foo: (number) -> number): () end
type T = <A...>(A...) -> number
local t: T
-- OK, as a function that takes some generic pack of arguments can receive a `number` as well.
f(t)
```
* Report an error when a type pack is provided to a generic alias that
can receive a type _and_ a type pack, as in:
```luau
type Y<T = string, U... = ...string> = { a: (T) -> U... }
-- Now errors as you must provide a type before the pack.
local a: Y<...number>
```
* Fix an instance of generics leaking when returning a function from
another function with explicitly defined generics. Fixes #1971.
* Cache `HasPropConstraint`s such that for every pair of subject type
and desired property, we only emit a single constraint and blocked type;
this incidentally fixes some bugs around inferring the types of
properties on `self`.
* Table types associated with table literals are now tracked specially
to make type checking more permissive, such as in:
```luau
type Foo = { name: string?, flag: boolean? }
local arr: {Foo} = {}
local function foo(arg: {name: string}?)
    local name = if arg and arg.name then arg.name else nil
    -- Previously would error as bidirectional inference would not
    -- kick in as often.
    table.insert(arr, {
        name = name or "",
        flag = name ~= nil and name ~= "",
    })
end
```

# Native Codegen
* Lowering to arm64 for some local heavy functions will now succeed
whereas prior they failed due to running out of registers for live
values.

--- 
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Annie Tang <annietang@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

Sync to upstream/release/689 (#1981)

# General Improvements

* Fix a crash that could occur when the `deprecated` attribute is used
in a syntactically incorrect way.
* Improve stack utilization in the parser. This should make it harder
for deeply nested constructs to exhaust the C stack.
* Fixed the `xpcall` continuation to handle errors handling the same way
as main execution path.
* The fuzzer now enables all Luau flags..
* The fuzzer will now add attributes and create table literal
expressions.
* The type of `rawget` is now `<K, V>(tab: {[K]: V}, k: K) -> V?` to
reflect the fact that it returns `nil` when the key is not present.
* Implement native codegen lowering for `vector.lerp`

# Autocomplete

* Autocomplete will also now suggest hot comments like `--!strict` and
`--!optimize`
* Incremental autocomplete had a bug where it wasn't selecting the
correct refinement of the autocomplete subject. This is now fixed.

# New Solver

* Fix an incorrect refinement that caused autocomplete to fail on
statements of the following form: `if #some_local.`
* Improve the error feedback when a type function is not passed required
arguments. (ie no `<>` afterward at all)
* Improvements to bidirectional table inference

## Internal Contributors

Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Annie Tang <annietang@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Ilya Rezvov <irezvov@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

---------

Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Varun Saini <61795485+vrn-sn@users.noreply.github.com>
Co-authored-by: Alexander Youngblood <ayoungblood@roblox.com>
Co-authored-by: Menarul Alam <malam@roblox.com>
Co-authored-by: Aviral Goel <agoel@roblox.com>
Co-authored-by: Vighnesh <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>

Sync to upstream/release/688 (#1968)

Sync to upstream/release/687 (#1954)

## What's Changed?

This week we have an update with an implementation for one of the RFCs
we had approved before, an improvement of the new type solver and a
small Lua 5.1 C API compatibility improvement.

* `@deprecated` attribute can now have a custom suggestion for a
replacement and a reason message as described in [deprecated attribute
parameters
RFC](https://rfcs.luau.org/syntax-attribute-functions-deprecated.html)

For example:
```luau
@[deprecated {reason = "foo suffers from performance issues", use = "bar"}]
local function foo()
    ...
end

-- Function 'foo' is deprecated, use 'bar' instead. foo suffers from performance issues
foo()
```

* `lua_cpcall` C API function has been restored both for compatibility
with Lua 5.1 and as a safe way to enter protected call environment to
work with Luau C API functions that may error

Instead of
```
if (!lua_checkstack(L, 2))
    return -1;
lua_pushcfunction(L, test, nullptr);
lua_pushlightuserdata(L, context);
int status = lua_pcall(L, 1, 0, 0);
```
you can simply do 
```
int status = lua_cpcall(L, test, context);
```

* In Luau CLI, required module return values can now have any type

## New Type Solver
- Additional improvements on type refinements used with external types
should fix some reported false positive errors where types refined to
`never`
- Fixed an issue in recursive refinement types in a form of `t1 where t1
= refine<t1, _>` getting 'stuck'
- Fixed an issue in subtyping of generic functions, it is now possible
to assign `<T>(T, (T) -> T) -> T` to `(number, <X>(X) -> X) -> number`
- Fixed an ICE caused by recursive types (Fixes #1686)
- Added additional iteration and recursion limits to stop the type
solver before system resources are used up

## Internal Contributors

Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Annie Tang <annietang@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Ilya Rezvov <irezvov@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

Sync to upstream/release/686 (#1948)

## General
This week has been spent mostly on fixing bugs in incremental
autocomplete as well as making the new Type Solver more stable.

- Fixes a bug where registered "require" aliases were case-sensitive
instead of case-insensitive.
### New Type Solver
- Adjust literal sub typing logic to account for unreduced type
functions
- Implement a number of subtyping stack utilization improvements
- Emit a single error if an internal type escapes a module's interface
- Checked function errors in the New Non Strict warn about incorrect
argument use with one-indexed positions, e.g. `argument #1 was used
incorrectly` instead of `argument #0 was used incorrectly`.
- Improvements to type function reduction that let us progress further
while reducing
- Augment the generalization system to not emit duplicate constraints.
- Fix a bug where we didn't seal tables in modules that failed to
complete typechecking.

### Fragment Autocomplete
- Provide richer autocomplete suggestions inside of for loops
- Provide richer autocomplete suggestions inside of interpolated string
expressions
- Improve the quality of error messages when typing out interpolated
strings.

### Compiler
- Fixes REX encoding of extended byte registers for the x86 assembly
code generation.
- Fixes for table shape constant data encoding

---
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Varun Saini <vsaini@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>

Sync to upstream/release/685 (#1940)

Another week, another release!

## Analysis
- Do not warn on unknown `require`s in non-strict mode.
- Improve `Luau::dump`'s output for `DenseHashMap`.
- Raise type checking errors when we would otherwise be leaking internal
error types from modules.
- Fix a crash that would sometimes occur when calling a function with an
incomplete type.
- Replace uses of `FFlag::LuauSolverV2` in `ClonePublicInterface` with a
`solverMode` field.
- Limit the number of constraints that can be dynamically created to
fail more gracefully in complex cases.
- Fix #1932.

---------

Co-authored-by: Alexander Youngblood <ayoungblood@roblox.com>
Co-authored-by: Andy Friesen <afriesen@roblox.com>
Co-authored-by: Ariel Weiss <aaronweiss@roblox.com>
Co-authored-by: Hunter Goldstein <hgoldstein@roblox.com>
Co-authored-by: Sora Kanosue <skanosue@roblox.com>
Co-authored-by: Talha Pathan <tpathan@roblox.com>
Co-authored-by: Vighnesh Vijay <vvijay@roblox.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>