Merge branch 'master' into merge

VM/include/lua.h

@@ -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);

VM/src/lapi.cpp

@@ -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);

docs/_pages/library.md

@@ -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

docs/_posts/2022-07-07-luau-recap-june-2022.md

@@ -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)

tests/Conformance.test.cpp

@@ -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;