resolve #1094 infer type by error

Author: sumneko

changelog.md

@@ -8,6 +8,17 @@
 
   if x == -- suggest `CONST.X` and `CONST.Y` here
   ```
+* `CHG` infer type by `error`
+  ```lua
+  ---@type integer?
+  local n
+
+  if not n then
+      error('n is nil')
+  end
+
+  print(n) -- `n` is `integer` here
+  ```
 * `FIX` with clients that support LSP 3.17 (VSCode), workspace diagnostics are triggered every time when opening a file.
 * `FIX` [#1204](https://github.com/sumneko/lua-language-server/issues/1204)
 * `FIX` [#1208](https://github.com/sumneko/lua-language-server/issues/1208)

script/parser/guide.lua

@@ -65,6 +65,7 @@ local type         = type
 ---@field hasGoTo?              true
 ---@field hasReturn?            true
 ---@field hasBreak?             true
+---@field hasError?             true
 ---@field _root                 parser.object
 
 ---@class guide

script/parser/newparser.lua

@@ -2818,6 +2818,17 @@ local function compileExpAsAction(exp)
     end
 
     if exp.type == 'call' then
+        if exp.node.special == 'error' then
+            for i = #Chunk, 1, -1 do
+                local block = Chunk[i]
+                if block.type == 'ifblock'
+                or block.type == 'elseifblock'
+                or block.type == 'else' then
+                    block.hasError = true
+                    break
+                end
+            end
+        end
         return exp
     end
 

script/vm/runner.lua

@@ -153,6 +153,7 @@ function mt:_lookInto(action, topNode, outNode)
             local neverReturn = subBlock.hasReturn
                             or  subBlock.hasGoTo
                             or  subBlock.hasBreak
+                            or  subBlock.hasError
             if not neverReturn then
                 blockNodes[#blockNodes+1] = blockNode
             end

test/type_inference/init.lua

@@ -2548,3 +2548,14 @@ while <?t?> ~= nil do
     print(t)
 end
 ]]
+
+TEST 'integer' [[
+---@type integer?
+local n
+
+if not n then
+    error('n is nil')
+end
+
+print(<?n?>)
+]]