test(diagnostics): add test suite for no-unknown-operations function calls

Author: NathanSnail

test/diagnostics/init.lua

@@ -110,6 +110,7 @@ check 'unnecessary-assert'
 check 'newfield-call'
 check 'newline-call'
 check 'not-yieldable'
+check 'no-unknown-operations'
 check 'param-type-mismatch'
 check 'redefined-local'
 check 'redundant-parameter'

test/diagnostics/no-unknown-operations.lua

@@ -0,0 +1,52 @@
+TEST [[
+local x = 5
+<!x()!>
+
+---@overload fun(): string
+local x = 5
+x()
+
+---@class x
+---@operator call(): string
+local x = {}
+x()
+]]
+
+TEST [[
+---@type nil
+local x
+<!x()!>
+
+---@overload fun(): string
+local x
+x()
+
+---@class x
+---@operator call(): string
+local x
+x()
+]]
+
+TEST [[
+---@type unknown
+local x
+x()
+]]
+
+TEST [[
+local function f()
+end
+f()
+]]
+
+TEST [[
+<!(0)()!>
+]]
+
+TEST [[
+<!("")()!>
+]]
+
+TEST [[
+(function() end)()
+]]