try (InputStream in = Files.newInputStream(userToolchainsFile.toPath())) {
                toolchains = new PersistedToolchains(new MavenToolchainsStaxReader().read(in));
            } catch (Exception e) {
                throw new MisconfiguredToolchainException(
                        "Cannot read toolchains file at " + userToolchainsFile.getAbsolutePath(), e);
            }

        } else if (userToolchainsFile != null) {

                    return new MappedList<>(result.getProblems(), MappedBuilderProblem::new);
                }
            };
        } catch (ToolchainsBuildingException e) {
            throw new ToolchainsBuilderException("Unable to build Toolchains", e);
        }
    }

    private static class MappedToolchainsSource implements org.apache.maven.building.Source {
        private final Source source;

        PersistedToolchains user = readToolchains(userSource, request, problems);

        PersistedToolchains effective = toolchainsMerger.merge(user, global, false, null);

        if (hasErrors(problems)) {
            throw new ToolchainsBuilderException("Error building toolchains", problems);
        }

        return new DefaultToolchainsBuilderResult(effective, problems);
    }