ruleguard: fix empty gogrep node slice interpolation (#345)

Author: quasilyte

analyzer/testdata/src/gocritic/deferUnlambda.go

@@ -0,0 +1,17 @@
+package gocritic
+
+import "fmt"
+
+func f(...interface{}) int { return 1 }
+
+const ten = 10
+
+func positiveTests() {
+	defer func() { f() }() // want `\Qdefer f()`
+
+	defer func() { f(1) }() // want `\Qdefer f(1)`
+
+	defer func() { f(ten, ten+1) }() // want `\Qdefer f(ten, ten+1)`
+
+	defer func() { fmt.Println("hello") }() // want `\Qdefer fmt.Println("hello")`
+}

analyzer/testdata/src/gocritic/rules.go

@@ -1,3 +1,4 @@
+//go:build ignore
 // +build ignore
 
 package gorules
@@ -264,3 +265,13 @@ func equalFold(m dsl.Matcher) {
 		Suggest(`bytes.EqualFold($x, $y)]`).
 		Report(`consider replacing with bytes.EqualFold($x, $y)`)
 }
+
+func deferUnlambda(m dsl.Matcher) {
+	m.Match(`defer func() { $f($*args) }()`).
+		Where(m["f"].Node.Is(`Ident`) && m["f"].Text != "panic" && m["f"].Text != "recover" && m["args"].Const).
+		Report("can rewrite as `defer $f($args)`")
+
+	m.Match(`defer func() { $pkg.$f($*args) }()`).
+		Where(m["f"].Node.Is(`Ident`) && m["args"].Const && m["pkg"].Object.Is(`PkgName`)).
+		Report("can rewrite as `defer $pkg.$f($args)`")
+}

ruleguard/runner.go

@@ -392,7 +392,7 @@ func (rr *rulesRunner) renderMessage(msg string, m matchData, truncate bool) str
 		// For example, pattern `func $_() $results { $*_ }` may
 		// match a nil *ast.FieldList for $results if executed
 		// against a function with no results.
-		if reflect.ValueOf(n).IsNil() {
+		if reflect.ValueOf(n).IsNil() && !gogrep.IsEmptyNodeSlice(n) {
 			continue
 		}
 		key := "$" + c.Name