if as, isAssign := s2.(*ast.AssignStmt); isAssign {
		// possibly a for statement with a range clause; check assignment operator
		if as.Tok != token.ASSIGN && as.Tok != token.DEFINE {
			p.errorExpected(as.TokPos, "'=' or ':='")
			return &ast.BadStmt{pos, body.End()}
		}
		// check lhs
		var key, value ast.Expr
		switch len(as.Lhs) {
		case 2:
			key, value = as.Lhs[0], as.Lhs[1]
		case 1:

		{"ArrayType.Lbrack", Field, 0},
		{"ArrayType.Len", Field, 0},
		{"AssignStmt", Type, 0},
		{"AssignStmt.Lhs", Field, 0},
		{"AssignStmt.Rhs", Field, 0},
		{"AssignStmt.Tok", Field, 0},
		{"AssignStmt.TokPos", Field, 0},
		{"Bad", Const, 0},
		{"BadDecl", Type, 0},
		{"BadDecl.From", Field, 0},
		{"BadDecl.To", Field, 0},
		{"BadExpr", Type, 0},
		{"BadExpr.From", Field, 0},
		{"BadExpr.To", Field, 0},

pkg go/ast, type AssignStmt struct
pkg go/ast, type AssignStmt struct, Lhs []Expr
pkg go/ast, type AssignStmt struct, Rhs []Expr
pkg go/ast, type AssignStmt struct, Tok token.Token
pkg go/ast, type AssignStmt struct, TokPos token.Pos
pkg go/ast, type BadDecl struct
pkg go/ast, type BadDecl struct, From token.Pos
pkg go/ast, type BadDecl struct, To token.Pos
pkg go/ast, type BadExpr struct
pkg go/ast, type BadExpr struct, From token.Pos