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Add unknown symbols to typecheck.md

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Alexander McCord 2020-06-18 23:36:14 -07:00
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docs/typecheck.md
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@ -27,6 +27,20 @@ foo = 1
However, in strict mode, the second snippet would be able to infer `number` for `foo` still.
## Unknown symbols
You may see this error a lot, and that's by design even in nonstrict mode.
Consider how often you're likely to assign a new value to a local variable. What if you accidentally misspelled it? Oops, it's now assigned globally and your local variable is still using the old value.
```lua
local someLocal = 1
soeLocal = 2 -- the bug
print(someLocal)
```
## Structural type system
Luau's type system is structural by default, which is to say that we inspect the shape of two tables to see if they are similar enough. This was the obvious choice because Lua 5.1 is inherently structural.