fix #863:false positive on return statement in a func lit passed to the deferred function (#870)

rule/defer.go

@@ -97,18 +97,21 @@ func (w lintDeferRule) Visit(node ast.Node) ast.Visitor {
 			w.newFailure("return in a defer function has no effect", n, 1.0, "logic", "return")
 		}
 	case *ast.CallExpr:
-		if !w.inADefer && isIdent(n.Fun, "recover") {
+		isCallToRecover := isIdent(n.Fun, "recover")
+		switch {
+		case !w.inADefer && isCallToRecover:
 			// func fn() { recover() }
 			//
 			// confidence is not 1 because recover can be in a function that is deferred elsewhere
 			w.newFailure("recover must be called inside a deferred function", n, 0.8, "logic", "recover")
-		} else if w.inADefer && !w.inAFuncLit && isIdent(n.Fun, "recover") {
+		case w.inADefer && !w.inAFuncLit && isCallToRecover:
 			// defer helper(recover())
 			//
 			// confidence is not truly 1 because this could be in a correctly-deferred func,
 			// but it is very likely to be a misunderstanding of defer's behavior around arguments.
 			w.newFailure("recover must be called inside a deferred function, this is executing recover immediately", n, 1, "logic", "immediate-recover")
 		}
+
 	case *ast.DeferStmt:
 		if isIdent(n.Call.Fun, "recover") {
 			// defer recover()
@@ -119,8 +122,13 @@ func (w lintDeferRule) Visit(node ast.Node) ast.Visitor {
 		}
 		w.visitSubtree(n.Call.Fun, true, false, false)
 		for _, a := range n.Call.Args {
+			switch a.(type) {
+			case *ast.FuncLit:
+				continue // too hard to analyze deferred calls with func literals args
+			default:
 				w.visitSubtree(a, true, false, false) // check arguments, they should not contain recover()
 			}
+		}
 
 		if w.inALoop {
 			w.newFailure("prefer not to defer inside loops", n, 1.0, "bad practice", "loop")
@@ -136,6 +144,7 @@ func (w lintDeferRule) Visit(node ast.Node) ast.Visitor {
 					w.newFailure("be careful when deferring calls to methods without pointer receiver", fn, 0.8, "bad practice", "method-call")
 				}
 			}
+
 		}
 		return nil
 	}

testdata/defer.go

@@ -33,3 +33,17 @@ func deferrer() {
 	// does not work, but not currently blocked.
 	defer helper(func() { recover() })
 }
+
+// Issue #863
+
+func verify(fn func() error) {
+	if err := fn(); err != nil {
+		panic(err)
+	}
+}
+
+func f() {
+	defer verify(func() error {
+		return nil
+	})
+}