6 files changed, 53 insertions, 8 deletions
diff --git a/script/core/diagnostics/assign-type-mismatch.lua b/script/core/diagnostics/assign-type-mismatch.lua
index 8080b2ec..e84e41df 100644
--- a/script/core/diagnostics/assign-type-mismatch.lua
+++ b/script/core/diagnostics/assign-type-mismatch.lua
@@ -5,6 +5,7 @@ local vm    = require 'vm'
 local await = require 'await'
 
 local checkTypes = {
+    'local',
     'setlocal',
     'setglobal',
     'setfield',
diff --git a/script/vm/compiler.lua b/script/vm/compiler.lua
index 46f6d0e9..ff1d9259 100644
--- a/script/vm/compiler.lua
+++ b/script/vm/compiler.lua
@@ -1000,14 +1000,12 @@ local function compileLocal(source)
         end
     end
     local hasMarkValue
-    if source.value then
-        if not hasMarkDoc or guide.isLiteral(source.value) then
-            hasMarkValue = true
-            if source.value.type == 'table' then
-                vm.setNode(source, source.value)
-            elseif source.value.type ~= 'nil' then
-                vm.setNode(source, vm.compileNode(source.value))
-            end
+    if not hasMarkDoc and source.value then
+        hasMarkValue = true
+        if source.value.type == 'table' then
+            vm.setNode(source, source.value)
+        elseif source.value.type ~= 'nil' then
+            vm.setNode(source, vm.compileNode(source.value))
         end
     end
     -- function x.y(self, ...) --> function x:y(...)
diff --git a/script/vm/infer.lua b/script/vm/infer.lua
index 25165de6..1f77b638 100644
--- a/script/vm/infer.lua
+++ b/script/vm/infer.lua
@@ -266,6 +266,16 @@ function mt:_eraseAlias(uri)
                         end
                     end
                 end
+                if set.type == 'doc.class' then
+                    if set.extends then
+                        for _, ext in ipairs(set.extends) do
+                            if ext.type == 'doc.extends.name' then
+                                local view = ext[1]
+                                drop[view] = true
+                            end
+                        end
+                    end
+                end
             end
             LOCK[n.name] = nil
             ::CONTINUE::
diff --git a/script/vm/type.lua b/script/vm/type.lua
index d132619c..7eb1b06f 100644
--- a/script/vm/type.lua
+++ b/script/vm/type.lua
@@ -171,6 +171,18 @@ function vm.isSubType(uri, child, parent, mark)
         mark[childName] = nil
     end
 
+    --[[
+    ---@class A: string
+
+    ---@type A
+    local x = '' --> `string` set to `A`
+    ]]
+    if  guide.isBasicType(childName)
+    and guide.isLiteral(child)
+    and vm.isSubType(uri, parentName, childName) then
+        return true
+    end
+
     return false
 end
 
diff --git a/test/diagnostics/type-check.lua b/test/diagnostics/type-check.lua
index 711211e8..34f7a492 100644
--- a/test/diagnostics/type-check.lua
+++ b/test/diagnostics/type-check.lua
@@ -479,5 +479,22 @@ n = nb
 ]]
 config.set(nil, 'Lua.type.weakUnionCheck', false)
 
+TEST [[
+---@class Option: string
+
+---@param x Option
+local function f(x) end
+
+---@type Option
+local x = 'aaa'
+
+f(x)
+]]
+
+TEST [[
+---@type number
+local <!x!> = 'aaa'
+]]
+
 config.remove(nil, 'Lua.diagnostics.disable', 'unused-local')
 config.remove(nil, 'Lua.diagnostics.disable', 'undefined-global')
diff --git a/test/type_inference/init.lua b/test/type_inference/init.lua
index 7b4185d7..4b745c0d 100644
--- a/test/type_inference/init.lua
+++ b/test/type_inference/init.lua
@@ -3142,3 +3142,10 @@ for _ in _ do
 end
 print(<?s?>)
 ]]
+
+TEST 'A' [[
+---@class A: string
+
+---@type A
+local <?s?> = ''
+]]