resolve #1285 ignore `nil` in `getfield`

4 files changed, 42 insertions, 1 deletions

diff --git a/changelog.md b/changelog.md
index 906ffa5a..b462cf58 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,6 +1,7 @@
 # changelog
 
 ## 3.5.0
+* `CHG` diagnostic: `type-check` ignores `nil` in `getfield`
 * `CHG` diagnostic: `---@diagnostic disable: <ERR_NAME>` can suppress syntax errors
 * `CHG` completion: `completion.callSnippet` no longer generate parameter types
 * `CHG` hover: show `---@type {x: number, y: number}` as detail instead of `table`
diff --git a/script/core/diagnostics/assign-type-mismatch.lua b/script/core/diagnostics/assign-type-mismatch.lua
index d98aa021..6809760c 100644
--- a/script/core/diagnostics/assign-type-mismatch.lua
+++ b/script/core/diagnostics/assign-type-mismatch.lua
@@ -82,11 +82,19 @@ return function (uri, callback)
             valueNode = valueNode:copy():removeOptional()
         end
 
+        if value.type == 'getfield'
+        or value.type == 'getindex' then
+            -- 由于无法对字段进行类型收窄，
+            -- 因此将假值移除再进行检查
+            valueNode = valueNode:copy():setTruthy()
+        end
+
         local varNode = vm.compileNode(source)
         if vm.canCastType(uri, varNode, valueNode) then
             return
         end
 
+        -- local Cat = setmetatable({}, {__index = Animal}) 允许逆变
         if  value.type == 'select'
         and value.sindex == 1
         and value.vararg
diff --git a/script/core/diagnostics/cast-local-type.lua b/script/core/diagnostics/cast-local-type.lua
index b7abcef6..c3d6e1bb 100644
--- a/script/core/diagnostics/cast-local-type.lua
+++ b/script/core/diagnostics/cast-local-type.lua
@@ -22,9 +22,17 @@ return function (uri, callback)
             return
         end
         for _, ref in ipairs(loc.ref) do
-            if ref.type == 'setlocal' then
+            if ref.type == 'setlocal' and ref.value then
                 await.delay()
                 local refNode = vm.compileNode(ref)
+                local value = ref.value
+
+                if value.type == 'getfield'
+                or value.type == 'getindex' then
+                    -- 由于无法对字段进行类型收窄，
+                    -- 因此将假值移除再进行检查
+                    refNode = refNode:copy():setTruthy()
+                end
 
                 if not vm.canCastType(uri, locNode, refNode) then
                     callback {
diff --git a/test/diagnostics/type-check.lua b/test/diagnostics/type-check.lua
index f1f14b48..cc60a969 100644
--- a/test/diagnostics/type-check.lua
+++ b/test/diagnostics/type-check.lua
@@ -664,5 +664,29 @@ local a = {}
 local <!b!> = setmetatable({}, {__index = a})
 ]]
 
+TEST [[
+---@class A
+---@field x number?
+local a
+
+---@class B
+---@field x number
+local b
+
+b.x = a.x
+]]
+
+TEST [[
+
+---@class A
+---@field x number?
+local a
+
+---@type number
+local t
+
+t = a.x
+]]
+
 config.remove(nil, 'Lua.diagnostics.disable', 'unused-local')
 config.remove(nil, 'Lua.diagnostics.disable', 'undefined-global')