add redundant-return diagnostic

4 files changed, 36 insertions, 0 deletions

diff --git a/locale/en-us/script.lua b/locale/en-us/script.lua
index fd423ced..c5e683b0 100644
--- a/locale/en-us/script.lua
+++ b/locale/en-us/script.lua
@@ -42,6 +42,7 @@ DIAG_COUNT_DOWN_LOOP    = 'Do you mean `{}` ?'
 DIAG_IMPLICIT_ANY       = 'Can not infer type.'
 DIAG_DEPRECATED         = 'Deprecated.'
 DIAG_DIFFERENT_REQUIRES = 'The same file is required with different names.'
+DIAG_REDUNDANT_RETURN   = 'Redundant return.'
 
 DIAG_CIRCLE_DOC_CLASS                 = 'Circularly inherited classes.'
 DIAG_DOC_FIELD_NO_CLASS               = 'The field must be defined after the class.'
diff --git a/locale/zh-cn/script.lua b/locale/zh-cn/script.lua
index cad50612..de204e63 100644
--- a/locale/zh-cn/script.lua
+++ b/locale/zh-cn/script.lua
@@ -42,6 +42,7 @@ DIAG_COUNT_DOWN_LOOP    = '你的意思是 `{}` 吗？'
 DIAG_IMPLICIT_ANY       = '无法推测出类型。'
 DIAG_DEPRECATED         = '已废弃。'
 DIAG_DIFFERENT_REQUIRES = '使用了不同的名字 require 了同一个文件。'
+DIAG_REDUNDANT_RETURN   = '冗余返回。'
 
 DIAG_CIRCLE_DOC_CLASS                 = '循环继承的类。'
 DIAG_DOC_FIELD_NO_CLASS               = '字段必须定义在类之后。'
diff --git a/script/core/diagnostics/redundant-return.lua b/script/core/diagnostics/redundant-return.lua
new file mode 100644
index 00000000..3d0fc566
--- /dev/null
+++ b/script/core/diagnostics/redundant-return.lua
@@ -0,0 +1,32 @@
+local files   = require 'files'
+local guide   = require 'parser.guide'
+local lang    = require 'language'
+local define  = require 'proto.define'
+
+-- reports 'return' or 'return nil' at the end of functions
+return function (uri, callback)
+    local ast = files.getState(uri)
+    if not ast then
+        return
+    end
+
+    guide.eachSourceType(ast.ast, 'return', function (source)
+        if not source.parent or source.parent.type ~= "function" then
+            return
+        end
+        for _, node in ipairs(source) do
+            while node and node.type == "paren" do
+                node = node.exp
+            end
+            if node and (node.type ~= "nil" or #node > 0) then
+                return
+            end
+        end
+        callback {
+            start   = source.start,
+            finish  = source.finish,
+            tags    = { define.DiagnosticTag.Unnecessary },
+            message = lang.script.DIAG_REDUNDANT_RETURN,
+        }
+    end)
+end
diff --git a/script/proto/define.lua b/script/proto/define.lua
index 63153423..713857af 100644
--- a/script/proto/define.lua
+++ b/script/proto/define.lua
@@ -29,6 +29,7 @@ m.DiagnosticDefaultSeverity = {
     ['newline-call']            = 'Information',
     ['newfield-call']           = 'Warning',
     ['redundant-parameter']     = 'Warning',
+    ['redundant-return']        = 'Warning',
     ['ambiguity-1']             = 'Warning',
     ['lowercase-global']        = 'Information',
     ['undefined-env-child']     = 'Information',
@@ -82,6 +83,7 @@ m.DiagnosticDefaultNeededFileStatus = {
     ['newline-call']            = 'Any',
     ['newfield-call']           = 'Any',
     ['redundant-parameter']     = 'Opened',
+    ['redundant-return']        = 'Opened',
     ['ambiguity-1']             = 'Any',
     ['lowercase-global']        = 'Any',
     ['undefined-env-child']     = 'Any',