Merge branch 'master' into merge

This commit is contained in:
Arseny Kapoulkine 2022-07-14 15:40:07 -07:00
commit 092e70115e
5 changed files with 105 additions and 4 deletions

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@ -64,14 +64,14 @@ enum lua_Type
LUA_TNIL = 0, /* must be 0 due to lua_isnoneornil */
LUA_TBOOLEAN = 1, /* must be 1 due to l_isfalse */
LUA_TLIGHTUSERDATA,
LUA_TNUMBER,
LUA_TVECTOR,
LUA_TSTRING, /* all types above this must be value types, all types below this must be GC types - see iscollectable */
LUA_TTABLE,
LUA_TFUNCTION,
LUA_TUSERDATA,
@ -300,6 +300,7 @@ LUA_API uintptr_t lua_encodepointer(lua_State* L, uintptr_t p);
LUA_API double lua_clock();
LUA_API void lua_setuserdatatag(lua_State* L, int idx, int tag);
LUA_API void lua_setuserdatadtor(lua_State* L, int tag, void (*dtor)(lua_State*, void*));
LUA_API void lua_clonefunction(lua_State* L, int idx);

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@ -1320,6 +1320,14 @@ void lua_unref(lua_State* L, int ref)
return;
}
void lua_setuserdatatag(lua_State* L, int idx, int tag)
{
api_check(L, unsigned(tag) < LUA_UTAG_LIMIT);
StkId o = index2addr(L, idx);
api_check(L, ttisuserdata(o));
uvalue(o)->tag = uint8_t(tag);
}
void lua_setuserdatadtor(lua_State* L, int tag, void (*dtor)(lua_State*, void*))
{
api_check(L, unsigned(tag) < LUA_UTAG_LIMIT);

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@ -683,7 +683,7 @@ Perform a bitwise `and` of all input numbers, and return `true` iff the result i
function bit32.extract(n: number, f: number, w: number?): number
```
Extracts bits at positions `[f..w]` and returns the resulting integer. `w` defaults to `f+1`, so a two-argument version of `extract` returns the bit value at position `f`.
Extracts bits of `n` at position `f` with a width of `w`, and returns the resulting integer. `w` defaults to `1`, so a two-argument version of `extract` returns the bit value at position `f`. Bits are indexed starting at 0. Errors if `f` and `f+w-1` are not between 0 and 31.
```
function bit32.lrotate(n: number, i: number): number
@ -701,7 +701,7 @@ Shifts `n` to the left by `i` bits (if `i` is negative, a right shift is perform
function bit32.replace(n: number, r: number, f: number, w: number?): number
```
Replaces bits at positions `[f..w]` of number `n` with `r` and returns the resulting integer. `w` defaults to `f+1`, so a three-argument version of `replace` changes one bit at position `f` to `r` (which should be 0 or 1) and returns the result.
Replaces bits of `n` at position `f` and width `w` with `r`, and returns the resulting integer. `w` defaults to `1`, so a three-argument version of `replace` changes one bit at position `f` to `r` (which should be 0 or 1) and returns the result. Bits are indexed starting at 0. Errors if `f` and `f+w-1` are not between 0 and 31.
```
function bit32.rrotate(n: number, i: number): number

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@ -0,0 +1,88 @@
---
layout: single
title: "Luau Recap: June 2022"
---
Luau is our new language that you can read more about at [https://luau-lang.org](https://luau-lang.org).
[Cross-posted to the [Roblox Developer Forum](https://devforum.roblox.com/t/luau-recap-june-2022/).]
# Lower bounds calculation
A common problem that Luau has is that it primarily works by inspecting expressions in your program and narrowing the _upper bounds_ of the values that can inhabit particular variables. In other words, each time we see a variable used, we eliminate possible sets of values from that variable's domain.
There are some important cases where this doesn't produce a helpful result. Take this function for instance:
```lua
function find_first_if(vec, f)
for i, e in ipairs(vec) do
if f(e) then
return i
end
end
return nil
end
```
Luau scans the function from top to bottom and first sees the line `return i`. It draws from this the inference that `find_first_if` must return the type of `i`, namely `number`.
This is fine, but things go sour when we see the line `return nil`. Since we are always narrowing, we take from this line the judgement that the return type of the function is `nil`. Since we have already concluded that the function must return `number`, Luau reports an error.
What we actually want to do in this case is to take these `return` statements as inferences about the _lower_ bound of the function's return type. Instead of saying "this function must return values of type `nil`," we should instead say "this function may _also_ return values of type `nil`."
Lower bounds calculation does precisely this. Moving forward, Luau will instead infer the type `number?` for the above function.
This does have one unfortunate consequence: If a function has no return type annotation, we will no longer ever report a type error on a `return` statement. We think this is the right balance but we'll be keeping an eye on things just to be sure.
Lower-bounds calculation is larger and a little bit riskier than other things we've been working on so we've set up a beta feature in Roblox Studio to enable them. It is called "Experimental Luau language features."
Please try it out and let us know what you think!
## Known bug
We have a known bug with certain kinds of cyclic types when lower-bounds calculation is enabled. The following, for instance, is known to be problematic.
```lua
type T = {T?}? -- spuriously reduces to {nil}?
```
We hope to have this fixed soon.
# All table literals now result in unsealed tables
Previously, the only way to create a sealed table was by with a literal empty table. We have relaxed this somewhat: Any table created by a `{}` expression is considered to be unsealed within the scope where it was created:
```lua
local T = {}
T.x = 5 -- OK
local V = {x=5}
V.y = 2 -- previously disallowed. Now OK.
function mkTable()
return {x = 5}
end
local U = mkTable()
U.y = 2 -- Still disallowed: U is sealed
```
# Other fixes
* Adjust indentation and whitespace when creating multiline string representations of types, resulting in types that are easier to read.
* Some small bugfixes to autocomplete
* Fix a case where accessing a nonexistent property of a table would not result in an error being reported.
* Improve parser recovery for the incorrect code `function foo() -> ReturnType` (the correct syntax is `function foo(): ReturnType`)
* Improve the parse error offered for code that improperly uses the `function` keyword to start a type eg `type T = function`
* Some small crash fixes and performance improvements
# Thanks!
A very special thanks to all of our open source contributors:
* [Allan N Jeremy](https://github.com/AllanJeremy)
* [Daniel Nachun](https://github.com/danielnachun)
* [JohnnyMorganz](https://github.com/JohnnyMorganz/)
* [Petri Häkkinen](https://github.com/petrihakkinen)
* [Qualadore](https://github.com/Qualadore)

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@ -1202,6 +1202,10 @@ TEST_CASE("UserdataApi")
CHECK(lua_touserdatatagged(L, -1, 41) == nullptr);
CHECK(lua_userdatatag(L, -1) == 42);
lua_setuserdatatag(L, -1, 43);
CHECK(lua_userdatatag(L, -1) == 43);
lua_setuserdatatag(L, -1, 42);
// user data with inline dtor
void* ud3 = lua_newuserdatadtor(L, 4, [](void* data) {
dtorhits += *(int*)data;