fix(types): add some return/parameter type annotations (#24867)

* fix(types): add some return/parameter type annotations

* fix(types): narrow stdpath parameter further

runtime/doc/lua.txt

@@ -1567,6 +1567,9 @@ vim.deprecate({name}, {alternative}, {version}, {plugin}, {backtrace})
 vim.inspect                                                    *vim.inspect()*
     Gets a human-readable representation of the given object.
 
+    Return: ~
+        (string)
+
     See also: ~
       • |vim.print()|
       • https://github.com/kikito/inspect.lua

runtime/lua/vim/_editor.lua

@@ -188,6 +188,7 @@ end
 ---@see |vim.print()|
 ---@see https://github.com/kikito/inspect.lua
 ---@see https://github.com/mpeterv/vinspect
+---@return string
 vim.inspect = vim.inspect
 
 do

runtime/lua/vim/_meta/vimfn.lua

@@ -3297,8 +3297,8 @@ function vim.fn.getpid() end
 ---   call setpos("'a", save_a_mark)
 --- <Also see |getcharpos()|, |getcurpos()| and |setpos()|.
 ---
---- @param expr any
---- @return any
+--- @param expr string
+--- @return integer[]
 function vim.fn.getpos(expr) end
 
 --- Returns a |List| with all the current quickfix errors.  Each
@@ -8827,8 +8827,8 @@ function vim.fn.stdioopen(opts) end
 ---   echo stdpath("config")
 --- <
 ---
---- @param what any
---- @return any
+--- @param what 'cache'|'config'|'config_dirs'|'data'|'data_dirs'|'log'|'run'|'state'
+--- @return string|string[]
 function vim.fn.stdpath(what) end
 
 --- Convert String {string} to a Float.  This mostly works the

src/nvim/eval.lua

@@ -4092,7 +4092,8 @@ M.funcs = {
 
     ]=],
     name = 'getpos',
-    params = { { 'expr', 'any' } },
+    params = { { 'expr', 'string' } },
+    returns = 'integer[]',
     signature = 'getpos({expr})',
   },
   getqflist = {
@@ -10459,7 +10460,8 @@ M.funcs = {
     ]=],
     fast = true,
     name = 'stdpath',
-    params = { { 'what', 'any' } },
+    params = { { 'what', "'cache'|'config'|'config_dirs'|'data'|'data_dirs'|'log'|'run'|'state'" } },
+    returns = 'string|string[]',
     signature = 'stdpath({what})',
   },
   state = {