fix: reporting within anonymous function

wrapcheck/testdata/issue_17_anon_function/main.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+)
+
+func main() {
+	var b bytes.Buffer
+
+	test := func() error {
+		return json.NewEncoder(&b).Encode("test")
+	}
+
+	fmt.Println(test())
+}

wrapcheck/wrapcheck.go

@@ -121,7 +121,20 @@ func run(cfg WrapcheckConfig) func(*analysis.Pass) (interface{}, error) {
 		}
 
 		for _, file := range pass.Files {
+			// Keep track of parents so that can can traverse upwards to check for
+			// FuncDecls and FuncLits.
+			var parents []ast.Node
+
 			ast.Inspect(file, func(n ast.Node) bool {
+				if n == nil {
+					// Pop, since we're done with this node and its children.
+					parents = parents[:len(parents)-1]
+				} else {
+					// Push this node on the stack, since its children will be visited
+					// next.
+					parents = append(parents, n)
+				}
+
 				ret, ok := n.(*ast.ReturnStmt)
 				if !ok {
 					return true
@@ -137,6 +150,17 @@ func run(cfg WrapcheckConfig) func(*analysis.Pass) (interface{}, error) {
 					// to handle it by checking the return params of the function.
 					retFn, ok := expr.(*ast.CallExpr)
 					if ok {
+						// If you go up, and the parent is a FuncLit, then don't report an
+						// error as you are in an anonymous function. If you are inside a
+						// FuncDecl, then continue as normal.
+						for i := len(parents) - 1; i > 0; i-- {
+							if _, ok := parents[i].(*ast.FuncLit); ok {
+								return true
+							} else if _, ok := parents[i].(*ast.FuncDecl); ok {
+								break
+							}
+						}
+
 						// If the return type of the function is a single error. This will not
 						// match an error within multiple return values, for that, the below
 						// tuple check is required.