SA9010: simplify implementation

Author: dominikh

staticcheck/sa9010/sa9010.go

@@ -48,53 +48,9 @@ function:
 var Analyzer = SCAnalyzer.Analyzer
 
 func run(pass *analysis.Pass) (any, error) {
-	checkIdent := func(c *ast.Ident) bool {
-		var (
-			obj = pass.TypesInfo.ObjectOf(c)
-			sig *types.Signature
-		)
-		switch f := obj.(type) {
-		case *types.Builtin:
-			return false
-		case *types.Func:
-			sig = f.Type().(*types.Signature)
-		case *types.Var:
-			switch ff := f.Type().(type) {
-			case *types.Signature:
-				sig = ff
-			case *types.Named:
-				sig = ff.Underlying().(*types.Signature)
-			}
-		}
-		r := sig.Results()
-		if r != nil && r.Len() == 1 {
-			_, ok := r.At(0).Type().(*types.Signature)
-			return ok
-		}
-		return false
-	}
-
 	fn := func(n ast.Node) {
-		var (
-			returnsFunc bool
-			def         = n.(*ast.DeferStmt)
-		)
-		switch c := def.Call.Fun.(type) {
-		case *ast.FuncLit: // defer func() { }()
-			r := c.Type.Results
-			if r != nil && len(r.List) == 1 {
-				_, returnsFunc = r.List[0].Type.(*ast.FuncType)
-			}
-		case *ast.Ident: // defer f()
-			returnsFunc = checkIdent(c)
-		case *ast.SelectorExpr: // defer t.f()
-			returnsFunc = checkIdent(c.Sel)
-		case *ast.IndexExpr: // defer f[int](0)
-			if id, ok := c.X.(*ast.Ident); ok {
-				returnsFunc = checkIdent(id)
-			}
-		}
-		if returnsFunc {
+		def := n.(*ast.DeferStmt)
+		if _, ok := pass.TypesInfo.TypeOf(def.Call).Underlying().(*types.Signature); ok {
 			report.Report(pass, def, "deferred return function not called")
 		}
 	}

staticcheck/sa9010/testdata/go1.0/example.com/deferr/deferr.go

@@ -68,9 +68,9 @@ func x() {
 	defer func(int) func(int) int { return func(int) int { return 0 } }(0) //@ diag(`deferred return function not called`)
 
 	// Function returns a function which returns another function. This is
-	// getting silly and is not checked.
-	defer silly1()()
-	defer func() func() func() {
+	// getting silly, but we do flag it.
+	defer silly1()()             //@ diag(`deferred return function not called`)
+	defer func() func() func() { //@ diag(`deferred return function not called`)
 		return func() func() {
 			return func() {}
 		}