fix: correct control flow graph for defer statements

_test/defer4.go

@@ -0,0 +1,23 @@
+package main
+
+import "sync"
+
+type T struct {
+	mu   sync.RWMutex
+	name string
+}
+
+func (t *T) get() string {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+	return t.name
+}
+
+var d = T{name: "test"}
+
+func main() {
+	println(d.get())
+}
+
+// Output:
+// test

interp/ast.go

@@ -200,7 +200,6 @@ const (
 	aCase
 	aCompositeLit
 	aDec
-	aDefer
 	aEqual
 	aGreater
 	aGreaterEqual
@@ -258,7 +257,6 @@ var actions = [...]string{
 	aCase:         "case",
 	aCompositeLit: "compositeLit",
 	aDec:          "--",
-	aDefer:        "defer",
 	aEqual:        "==",
 	aGreater:      ">",
 	aGetFunc:      "getFunc",
@@ -569,7 +567,7 @@ func (interp *Interpreter) ast(src, name string) (string, *node, error) {
 			st.push(addChild(&root, anc, pos, declStmt, aNop), nod)
 
 		case *ast.DeferStmt:
-			st.push(addChild(&root, anc, pos, deferStmt, aDefer), nod)
+			st.push(addChild(&root, anc, pos, deferStmt, aNop), nod)
 
 		case *ast.Ellipsis:
 			st.push(addChild(&root, anc, pos, ellipsisExpr, aNop), nod)

interp/cfg.go

@@ -936,7 +936,7 @@ func (interp *Interpreter) cfg(root *node, pkgID string) ([]*node, error) {
 			sc = sc.pop()
 			err = genRun(n)
 
-		case goStmt:
+		case deferStmt, goStmt:
 			wireChild(n)
 
 		case identExpr:

interp/run.go

@@ -29,7 +29,6 @@ var builtin = [...]bltnGenerator{
 	aCase:         _case,
 	aCompositeLit: arrayLit,
 	aDec:          dec,
-	aDefer:        _defer,
 	aEqual:        equal,
 	aGetFunc:      getFunc,
 	aGreater:      greater,
@@ -597,47 +596,6 @@ func genInterfaceWrapper(n *node, typ reflect.Type) func(*frame) reflect.Value {
 	}
 }
 
-func _defer(n *node) {
-	tnext := getExec(n.tnext)
-	values := make([]func(*frame) reflect.Value, len(n.child[0].child))
-	var method func(*frame) reflect.Value
-
-	for i, c := range n.child[0].child {
-		if c.typ.cat == funcT {
-			values[i] = genFunctionWrapper(c)
-		} else {
-			if c.recv != nil {
-				// defer a method on a binary obj
-				mi := c.val.(int)
-				m := genValue(c.child[0])
-				method = func(f *frame) reflect.Value { return m(f).Method(mi) }
-			}
-			values[i] = genValue(c)
-		}
-	}
-
-	if method != nil {
-		n.exec = func(f *frame) bltn {
-			val := make([]reflect.Value, len(values))
-			val[0] = method(f)
-			for i, v := range values[1:] {
-				val[i+1] = v(f)
-			}
-			f.deferred = append([][]reflect.Value{val}, f.deferred...)
-			return tnext
-		}
-	} else {
-		n.exec = func(f *frame) bltn {
-			val := make([]reflect.Value, len(values))
-			for i, v := range values {
-				val[i] = v(f)
-			}
-			f.deferred = append([][]reflect.Value{val}, f.deferred...)
-			return tnext
-		}
-	}
-}
-
 func call(n *node) {
 	goroutine := n.anc.kind == goStmt
 	var method bool
@@ -709,6 +667,21 @@ func call(n *node) {
 		}
 	}
 
+	if n.anc.kind == deferStmt {
+		// Store function call in frame for deferred execution.
+		value = genFunctionWrapper(n.child[0])
+		n.exec = func(f *frame) bltn {
+			val := make([]reflect.Value, len(values)+1)
+			val[0] = value(f)
+			for i, v := range values {
+				val[i+1] = v(f)
+			}
+			f.deferred = append([][]reflect.Value{val}, f.deferred...)
+			return tnext
+		}
+		return
+	}
+
 	n.exec = func(f *frame) bltn {
 		var def *node
 		var ok bool
@@ -893,8 +866,19 @@ func callBin(n *node) {
 	l := len(values)
 
 	switch {
+	case n.anc.kind == deferStmt:
+		// Store function call in frame for deferred execution.
+		n.exec = func(f *frame) bltn {
+			val := make([]reflect.Value, l+1)
+			val[0] = value(f)
+			for i, v := range values {
+				val[i+1] = v(f)
+			}
+			f.deferred = append([][]reflect.Value{val}, f.deferred...)
+			return tnext
+		}
 	case n.anc.kind == goStmt:
-		// Execute function in a goroutine, discard results
+		// Execute function in a goroutine, discard results.
 		n.exec = func(f *frame) bltn {
 			in := make([]reflect.Value, l)
 			for i, v := range values {
@@ -904,7 +888,7 @@ func callBin(n *node) {
 			return tnext
 		}
 	case fnext != nil:
-		// Handle branching according to boolean result
+		// Handle branching according to boolean result.
 		n.exec = func(f *frame) bltn {
 			in := make([]reflect.Value, l)
 			for i, v := range values {