// whose execution terminates."
				valid := false
				if t := b.enclosingTarget(name); t != nil {
					switch t.Stmt.(type) {
					case *syntax.SwitchStmt, *syntax.SelectStmt, *syntax.ForStmt:
						valid = true
					}
				}
				if !valid {
					check.errorf(s.Label, MisplacedLabel, "invalid break label %s", name)
					return
				}

			case syntax.Continue:

				// whose execution terminates."
				valid := false
				if t := b.enclosingTarget(name); t != nil {
					switch t.Stmt.(type) {
					case *ast.SwitchStmt, *ast.TypeSwitchStmt, *ast.SelectStmt, *ast.ForStmt, *ast.RangeStmt:
						valid = true
					}
				}
				if !valid {
					check.errorf(s.Label, MisplacedLabel, "invalid break label %s", name)
					return
				}

			case token.CONTINUE:

		// case *ExprStmt:
		case *SendStmt:
			m = n.Chan
		// case *DeclStmt:
		case *AssignStmt:
			m = n.Lhs
		// case *BranchStmt:
		// case *CallStmt:
		// case *ReturnStmt:
		// case *IfStmt:
		// case *ForStmt:
		// case *SwitchStmt:
		// case *SelectStmt:

		// helper nodes
		case *RangeClause:
			if n.Lhs != nil {
				m = n.Lhs
				continue
			}
			m = n.X
		// case *CaseClause:

		}
		Walk(v, n.Assign)
		Walk(v, n.Body)

	case *CommClause:
		if n.Comm != nil {
			Walk(v, n.Comm)
		}
		walkList(v, n.Body)

	case *SelectStmt:
		Walk(v, n.Body)

	case *ForStmt:
		if n.Init != nil {
			Walk(v, n.Init)
		}
		if n.Cond != nil {
			Walk(v, n.Cond)
		}
		if n.Post != nil {
			Walk(v, n.Post)
		}
		Walk(v, n.Body)

	case *RangeStmt: