annotate rust/hg-core/src/errors.rs @ 47347:73ddcedeaadf

dirstate-tree: Change status() results to not borrow DirstateMap The `status` function takes a `&'tree mut DirstateMap<'on_disk>` parameter. `'on_disk` borrows a read-only byte buffer with the contents of the `.hg/dirstate` file. `DirstateMap` internally uses represents file paths as `std::borrow::Cow<'on_disk, HgPath>`, which borrows the byte buffer when possible and allocates an owned string if not, such as for files added to the dirstate after it was loaded from disk. Previously the return type of of `status` has a `'tree`?lifetime, meaning it could borrow all paths from the `DirstateMap`. With this changeset, that lifetime is changed to `'on_disk` meaning that only paths from the byte buffer can be borrowed, and paths allocated by `DirstateMap` must be copied. Usually most paths are in the byte buffer, and most paths are not part of the return value of `status`, so the number of extra copies should be small. This change will enable `status` to mutate the `DirstateMap` after it has finished constructing its return value. Previously such mutation would be prevented by possible on-going borrows. Differential Revision: https://phab.mercurial-scm.org/D10824
author Simon Sapin <simon.sapin@octobus.net>
date Fri, 28 May 2021 20:07:27 +0200
parents bcdcb4423ae3
children 6e49769b7f97
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 use crate::config::ConfigValueParseError;
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2 use std::fmt;
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3
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4 /// Common error cases that can happen in many different APIs
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5 #[derive(Debug, derive_more::From)]
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6 pub enum HgError {
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7 IoError {
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8 error: std::io::Error,
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9 context: IoErrorContext,
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10 },
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11
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12 /// A file under `.hg/` normally only written by Mercurial is not in the
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13 /// expected format. This indicates a bug in Mercurial, filesystem
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14 /// corruption, or hardware failure.
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15 ///
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16 /// The given string is a short explanation for users, not intended to be
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17 /// machine-readable.
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18 CorruptedRepository(String),
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19
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20 /// The respository or requested operation involves a feature not
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21 /// supported by the Rust implementation. Falling back to the Python
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22 /// implementation may or may not work.
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23 ///
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24 /// The given string is a short explanation for users, not intended to be
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25 /// machine-readable.
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26 UnsupportedFeature(String),
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27
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28 /// Operation cannot proceed for some other reason.
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29 ///
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30 /// The given string is a short explanation for users, not intended to be
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31 /// machine-readable.
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32 Abort(String),
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33
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34 /// A configuration value is not in the expected syntax.
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35 ///
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36 /// These errors can happen in many places in the code because values are
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37 /// parsed lazily as the file-level parser does not know the expected type
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38 /// and syntax of each value.
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39 #[from]
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40 ConfigValueParseError(ConfigValueParseError),
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41 }
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42
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43 /// Details about where an I/O error happened
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44 #[derive(Debug)]
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45 pub enum IoErrorContext {
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46 ReadingFile(std::path::PathBuf),
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47 WritingFile(std::path::PathBuf),
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48 RemovingFile(std::path::PathBuf),
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49 RenamingFile {
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50 from: std::path::PathBuf,
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51 to: std::path::PathBuf,
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52 },
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53 /// `std::fs::canonicalize`
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54 CanonicalizingPath(std::path::PathBuf),
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55 /// `std::env::current_dir`
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56 CurrentDir,
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57 /// `std::env::current_exe`
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58 CurrentExe,
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59 }
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60
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61 impl HgError {
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62 pub fn corrupted(explanation: impl Into<String>) -> Self {
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63 // TODO: capture a backtrace here and keep it in the error value
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64 // to aid debugging?
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65 // https://doc.rust-lang.org/std/backtrace/struct.Backtrace.html
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66 HgError::CorruptedRepository(explanation.into())
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67 }
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68
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69 pub fn unsupported(explanation: impl Into<String>) -> Self {
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70 HgError::UnsupportedFeature(explanation.into())
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71 }
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72 pub fn abort(explanation: impl Into<String>) -> Self {
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73 HgError::Abort(explanation.into())
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74 }
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75 }
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76
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77 // TODO: use `DisplayBytes` instead to show non-Unicode filenames losslessly?
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78 impl fmt::Display for HgError {
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79 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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80 match self {
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81 HgError::Abort(explanation) => write!(f, "{}", explanation),
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82 HgError::IoError { error, context } => {
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83 write!(f, "abort: {}: {}", context, error)
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84 }
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85 HgError::CorruptedRepository(explanation) => {
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86 write!(f, "abort: {}", explanation)
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87 }
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88 HgError::UnsupportedFeature(explanation) => {
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89 write!(f, "unsupported feature: {}", explanation)
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90 }
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91 HgError::ConfigValueParseError(error) => error.fmt(f),
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92 }
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93 }
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94 }
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95
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96 // TODO: use `DisplayBytes` instead to show non-Unicode filenames losslessly?
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97 impl fmt::Display for IoErrorContext {
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98 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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99 match self {
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100 IoErrorContext::ReadingFile(path) => {
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101 write!(f, "when reading {}", path.display())
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102 }
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103 IoErrorContext::WritingFile(path) => {
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104 write!(f, "when writing {}", path.display())
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105 }
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106 IoErrorContext::RemovingFile(path) => {
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107 write!(f, "when removing {}", path.display())
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108 }
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109 IoErrorContext::RenamingFile { from, to } => write!(
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110 f,
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111 "when renaming {} to {}",
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112 from.display(),
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113 to.display()
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114 ),
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115 IoErrorContext::CanonicalizingPath(path) => {
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116 write!(f, "when canonicalizing {}", path.display())
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117 }
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118 IoErrorContext::CurrentDir => {
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119 write!(f, "error getting current working directory")
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120 }
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121 IoErrorContext::CurrentExe => {
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122 write!(f, "error getting current executable")
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123 }
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124 }
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125 }
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126 }
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127
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128 pub trait IoResultExt<T> {
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129 /// Annotate a possible I/O error as related to a reading a file at the
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130 /// given path.
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131 ///
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132 /// This allows printing something like “File not found when reading
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133 /// example.txt” instead of just “File not found”.
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134 ///
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135 /// Converts a `Result` with `std::io::Error` into one with `HgError`.
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136 fn when_reading_file(self, path: &std::path::Path) -> Result<T, HgError>;
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137
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138 fn with_context(
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139 self,
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140 context: impl FnOnce() -> IoErrorContext,
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141 ) -> Result<T, HgError>;
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142 }
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143
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144 impl<T> IoResultExt<T> for std::io::Result<T> {
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145 fn when_reading_file(self, path: &std::path::Path) -> Result<T, HgError> {
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146 self.with_context(|| IoErrorContext::ReadingFile(path.to_owned()))
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147 }
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148
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149 fn with_context(
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150 self,
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151 context: impl FnOnce() -> IoErrorContext,
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152 ) -> Result<T, HgError> {
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153 self.map_err(|error| HgError::IoError {
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154 error,
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155 context: context(),
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156 })
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157 }
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158 }
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159
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160 pub trait HgResultExt<T> {
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161 /// Handle missing files separately from other I/O error cases.
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162 ///
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163 /// Wraps the `Ok` type in an `Option`:
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164 ///
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165 /// * `Ok(x)` becomes `Ok(Some(x))`
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166 /// * An I/O "not found" error becomes `Ok(None)`
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167 /// * Other errors are unchanged
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168 fn io_not_found_as_none(self) -> Result<Option<T>, HgError>;
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169 }
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170
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171 impl<T> HgResultExt<T> for Result<T, HgError> {
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172 fn io_not_found_as_none(self) -> Result<Option<T>, HgError> {
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173 match self {
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174 Ok(x) => Ok(Some(x)),
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175 Err(HgError::IoError { error, .. })
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176 if error.kind() == std::io::ErrorKind::NotFound =>
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177 {
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178 Ok(None)
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179 }
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180 Err(other_error) => Err(other_error),
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181 }
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182 }
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183 }