diff --git a/.github/workflows/rust.yaml b/.github/workflows/rust.yaml
index 0b6cf7a..612dd8c 100644
--- a/.github/workflows/rust.yaml
+++ b/.github/workflows/rust.yaml
@@ -7,7 +7,16 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v1
+    - name: Update
+      run: rustup update stable
+    - name: Version
+      run: |
+        rustup --version
+        cargo --version
+        cargo clippy --version
     - name: Build
       run: cargo build --verbose
     - name: Test
       run: cargo test --verbose
+    - name: Lint
+      run: cargo clippy
diff --git a/Cargo.lock b/Cargo.lock
index 2457e83..75d699a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -13,22 +13,21 @@ name = "ansi_term"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "atty"
-version = "0.2.11"
+version = "0.2.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
- "termion 1.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "bitflags"
-version = "1.0.4"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -50,11 +49,11 @@ version = "2.33.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "atty 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "strsim 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicode-width 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-width 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -78,7 +77,7 @@ name = "heck"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "unicode-segmentation 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-segmentation 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -103,7 +102,8 @@ dependencies = [
  "serde_bytes 0.11.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "sha1 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "snafu 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "structopt 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "static_assertions 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "structopt 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "walkdir 2.2.9 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -134,11 +134,6 @@ name = "memchr"
 version = "2.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
-[[package]]
-name = "numtoa"
-version = "0.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
 [[package]]
 name = "percent-encoding"
 version = "2.1.0"
@@ -151,17 +146,31 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "proc-macro-error"
-version = "0.2.6"
+version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-error-attr 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustversion 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustversion 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn-mid 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.6"
+version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -172,7 +181,7 @@ name = "quote"
 version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -214,17 +223,9 @@ dependencies = [
 
 [[package]]
 name = "redox_syscall"
-version = "0.1.54"
+version = "0.1.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
-[[package]]
-name = "redox_termios"
-version = "0.1.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
 [[package]]
 name = "regex"
 version = "1.3.1"
@@ -246,7 +247,17 @@ name = "remove_dir_all"
 version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rustversion"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -295,9 +306,9 @@ name = "serde_derive"
 version = "1.0.104"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -324,11 +335,16 @@ name = "snafu-derive"
 version = "0.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "static_assertions"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "strsim"
 version = "0.8.0"
@@ -336,35 +352,45 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "structopt"
-version = "0.3.5"
+version = "0.3.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "structopt-derive 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "structopt-derive 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "structopt-derive"
-version = "0.3.5"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro-error 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-error 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "syn"
-version = "1.0.11"
+version = "1.0.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "syn-mid"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "tempfile"
 version = "3.1.0"
@@ -373,20 +399,9 @@ dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "remove_dir_all 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
-name = "termion"
-version = "1.5.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
- "numtoa 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -394,7 +409,7 @@ name = "textwrap"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "unicode-width 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-width 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -423,12 +438,12 @@ dependencies = [
 
 [[package]]
 name = "unicode-segmentation"
-version = "1.3.0"
+version = "1.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "unicode-width"
-version = "0.1.5"
+version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -457,7 +472,7 @@ version = "2.2.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "same-file 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi-util 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -468,7 +483,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "winapi"
-version = "0.3.7"
+version = "0.3.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -485,7 +500,7 @@ name = "winapi-util"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -496,8 +511,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [metadata]
 "checksum aho-corasick 0.7.6 (registry+https://github.com/rust-lang/crates.io-index)" = "58fb5e95d83b38284460a5fda7d6470aa0b8844d283a0b614b8535e880800d2d"
 "checksum ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
-"checksum atty 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "9a7d5b8723950951411ee34d271d99dddcc2035a16ab25310ea2c8cfd4369652"
-"checksum bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "228047a76f468627ca71776ecdebd732a3423081fcf5125585bcd7c49886ce12"
+"checksum atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)" = "1803c647a3ec87095e7ae7acfca019e98de5ec9a7d01343f611cf3152ed71a90"
+"checksum bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
 "checksum c2-chacha 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "214238caa1bf3a496ec3392968969cab8549f96ff30652c9e56885329315f6bb"
 "checksum cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 "checksum clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5067f5bb2d80ef5d68b4c87db81601f0b75bca627bc2ef76b141d7b846a3c6d9"
@@ -510,21 +525,21 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum matches 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)" = "7ffc5c5338469d4d3ea17d269fa8ea3512ad247247c30bd2df69e68309ed0a08"
 "checksum md5 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "490cc448043f947bae3cbee9c203358d62dbee0db12107a74be5c30ccfd09771"
 "checksum memchr 2.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "88579771288728879b57485cc7d6b07d648c9f0141eb955f8ab7f9d45394468e"
-"checksum numtoa 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b8f8bdf33df195859076e54ab11ee78a1b208382d3a26ec40d142ffc1ecc49ef"
 "checksum percent-encoding 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d4fd5641d01c8f18a23da7b6fe29298ff4b55afcccdf78973b24cf3175fee32e"
 "checksum ppv-lite86 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "74490b50b9fbe561ac330df47c08f3f33073d2d00c150f719147d7c54522fa1b"
-"checksum proc-macro-error 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "aeccfe4d5d8ea175d5f0e4a2ad0637e0f4121d63bd99d356fb1f39ab2e7c6097"
-"checksum proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)" = "9c9e470a8dc4aeae2dee2f335e8f533e2d4b347e1434e5671afc49b054592f27"
+"checksum proc-macro-error 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "53c98547ceaea14eeb26fcadf51dc70d01a2479a7839170eae133721105e4428"
+"checksum proc-macro-error-attr 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c2bf5d493cf5d3e296beccfd61794e445e830dfc8070a9c248ad3ee071392c6c"
+"checksum proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)" = "0319972dcae462681daf4da1adeeaa066e3ebd29c69be96c6abb1259d2ee2bcc"
 "checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe"
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 "checksum rand_chacha 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "03a2a90da8c7523f554344f921aa97283eadf6ac484a6d2a7d0212fa7f8d6853"
 "checksum rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "90bde5296fc891b0cef12a6d03ddccc162ce7b2aff54160af9338f8d40df6d19"
 "checksum rand_hc 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ca3129af7b92a17112d59ad498c6f81eaf463253766b90396d39ea7a39d6613c"
-"checksum redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)" = "12229c14a0f65c4f1cb046a3b52047cdd9da1f4b30f8a39c5063c8bae515e252"
-"checksum redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7e891cfe48e9100a70a3b6eb652fef28920c117d366339687bd5576160db0f76"
+"checksum redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)" = "2439c63f3f6139d1b57529d16bc3b8bb855230c8efcc5d3a896c8bea7c3b1e84"
 "checksum regex 1.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "dc220bd33bdce8f093101afe22a037b8eb0e5af33592e6a9caafff0d4cb81cbd"
 "checksum regex-syntax 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)" = "11a7e20d1cce64ef2fed88b66d347f88bd9babb82845b2b858f3edbf59a4f716"
 "checksum remove_dir_all 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "4a83fa3702a688b9359eccba92d153ac33fd2e8462f9e0e3fdf155239ea7792e"
+"checksum rustversion 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3a0538bd897e17257b0128d2fd95c2ed6df939374073a36166051a79e2eb7986"
 "checksum same-file 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "585e8ddcedc187886a30fa705c47985c3fa88d06624095856b36ca0b82ff4421"
 "checksum serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)" = "414115f25f818d7dfccec8ee535d76949ae78584fc4f79a6f45a904bf8ab4449"
 "checksum serde_bencode 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9b79ce11369638af2fea08e00390316304c5b5e1b7a53d58ace925152b657443"
@@ -535,24 +550,25 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum smallvec 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "44e59e0c9fa00817912ae6e4e6e3c4fe04455e75699d06eedc7d85917ed8e8f4"
 "checksum snafu 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "41207ca11f96a62cd34e6b7fdf73d322b25ae3848eb9d38302169724bb32cf27"
 "checksum snafu-derive 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "4c5e338c8b0577457c9dda8e794b6ad7231c96e25b1b0dd5842d52249020c1c0"
+"checksum static_assertions 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
 "checksum strsim 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
-"checksum structopt 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "30b3a3e93f5ad553c38b3301c8a0a0cec829a36783f6a0c467fc4bf553a5f5bf"
-"checksum structopt-derive 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "ea692d40005b3ceba90a9fe7a78fa8d4b82b0ce627eebbffc329aab850f3410e"
-"checksum syn 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)" = "dff0acdb207ae2fe6d5976617f887eb1e35a2ba52c13c7234c790960cdad9238"
+"checksum structopt 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)" = "884ae79d6aad1e738f4a70dff314203fd498490a63ebc4d03ea83323c40b7b72"
+"checksum structopt-derive 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0a97f829a34a0a9d5b353a881025a23b8c9fd09d46be6045df6b22920dbd7a93"
+"checksum syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)" = "1e4ff033220a41d1a57d8125eab57bf5263783dfdcc18688b1dacc6ce9651ef8"
+"checksum syn-mid 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9fd3937748a7eccff61ba5b90af1a20dbf610858923a9192ea0ecb0cb77db1d0"
 "checksum tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
-"checksum termion 1.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "dde0593aeb8d47accea5392b39350015b5eccb12c0d98044d856983d89548dea"
 "checksum textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d326610f408c7a4eb6f51c37c330e496b08506c9457c9d34287ecc38809fb060"
 "checksum thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c6b53e329000edc2b34dbe8545fd20e55a333362d0a321909685a19bd28c3f1b"
 "checksum unicode-bidi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "49f2bd0c6468a8230e1db229cff8029217cf623c767ea5d60bfbd42729ea54d5"
 "checksum unicode-normalization 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)" = "b561e267b2326bb4cebfc0ef9e68355c7abe6c6f522aeac2f5bf95d56c59bdcf"
-"checksum unicode-segmentation 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1967f4cdfc355b37fd76d2a954fb2ed3871034eb4f26d60537d88795cfc332a9"
-"checksum unicode-width 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "882386231c45df4700b275c7ff55b6f3698780a650026380e72dabe76fa46526"
+"checksum unicode-segmentation 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e83e153d1053cbb5a118eeff7fd5be06ed99153f00dbcd8ae310c5fb2b22edc0"
+"checksum unicode-width 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)" = "caaa9d531767d1ff2150b9332433f32a24622147e5ebb1f26409d5da67afd479"
 "checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
 "checksum url 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "75b414f6c464c879d7f9babf951f23bc3743fb7313c081b2e6ca719067ea9d61"
 "checksum vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "05c78687fb1a80548ae3250346c3db86a80a7cdd77bda190189f2d0a0987c81a"
 "checksum walkdir 2.2.9 (registry+https://github.com/rust-lang/crates.io-index)" = "9658c94fa8b940eab2250bd5a457f9c48b748420d71293b165c8cdbe2f55f71e"
 "checksum wasi 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b89c3ce4ce14bdc6fb6beaf9ec7928ca331de5df7e5ea278375642a2f478570d"
-"checksum winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)" = "f10e386af2b13e47c89e7236a7a14a086791a2b88ebad6df9bf42040195cf770"
+"checksum winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)" = "8093091eeb260906a183e6ae1abdba2ef5ef2257a21801128899c3fc699229c6"
 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 "checksum winapi-util 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7168bab6e1daee33b4557efd0e95d5ca70a03706d39fa5f3fe7a236f584b03c9"
 "checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
diff --git a/Cargo.toml b/Cargo.toml
index 4da7f09..b30477c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,6 +23,7 @@ structopt     = "0.3"
 tempfile      = "3"
 url           = "2"
 walkdir       = "2"
+static_assertions = "1.1.0"
 
 [dependencies.serde]
 version = "1"
diff --git a/justfile b/justfile
index f206d91..41a9f82 100644
--- a/justfile
+++ b/justfile
@@ -17,6 +17,13 @@ done BRANCH:
 	git diff --no-ext-diff --quiet --exit-code {{BRANCH}}
 	git branch -D {{BRANCH}}
 
+test:
+	cargo test
+
+# lint code
+lint:
+	cargo clippy
+
 # retrieve large collection of torrents from the Internet Archive
 get-torrents:
 	aria2c \
diff --git a/src/bencode.rs b/src/bencode.rs
index e245529..84ed810 100644
--- a/src/bencode.rs
+++ b/src/bencode.rs
@@ -153,7 +153,7 @@ impl<'buffer> Parser<'buffer> {
     Ok(&self.buffer[start..self.index])
   }
 
-  fn parse_digits(&mut self, digits: &[u8]) -> Result<u64, Error> {
+  fn parse_digits(digits: &[u8]) -> Result<u64, Error> {
     if digits.is_empty() {
       return Err(EmptyInteger);
     }
@@ -190,7 +190,7 @@ impl<'buffer> Parser<'buffer> {
 
     self.expect(b'e')?;
 
-    let value = self.parse_digits(digits)?;
+    let value = Self::parse_digits(digits)?;
 
     if value == 0 && negative {
       return Err(NegativeZero);
@@ -250,7 +250,7 @@ impl<'buffer> Parser<'buffer> {
 
     self.expect(b':')?;
 
-    let len = self.parse_digits(digits)?;
+    let len = Self::parse_digits(digits)?;
 
     let start = self.index;
     for _ in 0..len {
diff --git a/src/common.rs b/src/common.rs
index b8297cc..d120871 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -3,6 +3,7 @@ pub(crate) use std::{
   borrow::Cow,
   cmp::{Ordering, Reverse},
   collections::{BTreeMap, HashMap},
+  convert::TryInto,
   env,
   ffi::{OsStr, OsString},
   fmt::{self, Display, Formatter},
@@ -12,7 +13,7 @@ pub(crate) use std::{
   path::{Path, PathBuf},
   process, str,
   time::{SystemTime, SystemTimeError},
-  u64, usize,
+  usize,
 };
 
 // dependencies
@@ -21,6 +22,7 @@ pub(crate) use regex::{Regex, RegexSet};
 pub(crate) use serde::{Deserialize, Serialize};
 pub(crate) use sha1::Sha1;
 pub(crate) use snafu::{ResultExt, Snafu};
+pub(crate) use static_assertions::const_assert;
 pub(crate) use structopt::StructOpt;
 pub(crate) use url::Url;
 pub(crate) use walkdir::WalkDir;
@@ -29,7 +31,9 @@ pub(crate) use walkdir::WalkDir;
 pub(crate) use crate::{bencode, consts, error, torrent};
 
 // traits
-pub(crate) use crate::{path_ext::PathExt, reckoner::Reckoner};
+pub(crate) use crate::{
+  into_u64::IntoU64, into_usize::IntoUsize, path_ext::PathExt, reckoner::Reckoner,
+};
 
 // structs and enums
 pub(crate) use crate::{
diff --git a/src/environment.rs b/src/environment.rs
index 26c579a..bf5935b 100644
--- a/src/environment.rs
+++ b/src/environment.rs
@@ -3,32 +3,32 @@ use crate::common::*;
 pub(crate) struct Environment {
   args: Vec<String>,
   dir: Box<dyn AsRef<Path>>,
-  err: Box<dyn Write>,
+  pub(crate) err: Box<dyn Write>,
 }
 
 impl Environment {
-  pub(crate) fn main() -> Environment {
+  pub(crate) fn main() -> Self {
     let dir = match env::current_dir() {
       Ok(dir) => dir,
       Err(error) => panic!("Failed to get current directory: {}", error),
     };
 
-    Environment::new(dir, io::stderr(), env::args())
+    Self::new(dir, io::stderr(), env::args())
   }
 
-  pub(crate) fn run(&self) -> Result<(), Error> {
+  pub(crate) fn run(&mut self) -> Result<(), Error> {
     Opt::from_iter_safe(&self.args)?.run(self)
   }
 
-  pub(crate) fn new<D, E, S, I>(dir: D, err: E, args: I) -> Environment
+  pub(crate) fn new<D, E, S, I>(dir: D, err: E, args: I) -> Self
   where
     D: AsRef<Path> + 'static,
     E: Write + 'static,
     S: Into<String>,
     I: IntoIterator<Item = S>,
   {
-    Environment {
-      args: args.into_iter().map(|s| s.into()).collect(),
+    Self {
+      args: args.into_iter().map(Into::into).collect(),
       dir: Box::new(dir),
       err: Box::new(err),
     }
diff --git a/src/err.rs b/src/err.rs
new file mode 100644
index 0000000..0b5f2bd
--- /dev/null
+++ b/src/err.rs
@@ -0,0 +1,8 @@
+macro_rules! err {
+  ($env:expr, $fmt:expr) => {
+    write!($env.err, $fmt).context(crate::error::Stderr)?;
+  };
+  ($env:expr, $fmt:expr, $($arg:tt)*) => {
+    write!($env.err, $fmt, $($arg)*).context(crate::error::Stderr)?;
+  };
+}
diff --git a/src/errln.rs b/src/errln.rs
new file mode 100644
index 0000000..0e6e1c8
--- /dev/null
+++ b/src/errln.rs
@@ -0,0 +1,11 @@
+macro_rules! errln {
+  ($env:expr) => {
+    writeln!($env.err, "").context(crate::error::Stderr)?;
+  };
+  ($env:expr, $fmt:expr) => {
+    writeln!($env.err, $fmt).context(crate::error::Stderr)?;
+  };
+  ($env:expr, $fmt:expr, $($arg:tt)*) => {
+    writeln!($env.err, $fmt, $($arg)*).context(crate::error::Stderr)?;
+  };
+}
diff --git a/src/error.rs b/src/error.rs
index 7ba16d4..9ab639e 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -9,6 +9,8 @@ pub(crate) enum Error {
   Clap { source: clap::Error },
   #[snafu(display("I/O error at `{}`: {}", path.display(), source))]
   Filesystem { source: io::Error, path: PathBuf },
+  #[snafu(display("Failed to write to standard error stream: {}", source))]
+  Stderr { source: io::Error },
   #[snafu(display("Serialization failed: {}", source))]
   Serialize { source: serde_bencode::Error },
   #[snafu(display("Filename was not valid unicode: {}", filename.to_string_lossy()))]
@@ -31,29 +33,29 @@ pub(crate) enum Error {
 }
 
 impl From<clap::Error> for Error {
-  fn from(source: clap::Error) -> Error {
-    Error::Clap { source }
+  fn from(source: clap::Error) -> Self {
+    Self::Clap { source }
   }
 }
 
 impl From<serde_bencode::Error> for Error {
-  fn from(source: serde_bencode::Error) -> Error {
-    Error::Serialize { source }
+  fn from(source: serde_bencode::Error) -> Self {
+    Self::Serialize { source }
   }
 }
 
 impl From<SystemTimeError> for Error {
-  fn from(source: SystemTimeError) -> Error {
-    Error::SystemTime { source }
+  fn from(source: SystemTimeError) -> Self {
+    Self::SystemTime { source }
   }
 }
 
 impl From<walkdir::Error> for Error {
-  fn from(walkdir_error: walkdir::Error) -> Error {
+  fn from(walkdir_error: walkdir::Error) -> Self {
     let path = walkdir_error.path().unwrap().to_owned();
 
     if let Some(source) = walkdir_error.into_io_error() {
-      Error::Filesystem { source, path }
+      Self::Filesystem { source, path }
     } else {
       unreachable!("Encountered unexpected walkdir error")
     }
diff --git a/src/hasher.rs b/src/hasher.rs
index 8be5e52..d6aa232 100644
--- a/src/hasher.rs
+++ b/src/hasher.rs
@@ -5,7 +5,7 @@ pub(crate) struct Hasher {
   length: u64,
   md5sum: bool,
   piece_bytes_hashed: u64,
-  piece_length: u64,
+  piece_length: u32,
   pieces: Vec<u8>,
   sha1: Sha1,
 }
@@ -14,14 +14,14 @@ impl Hasher {
   pub(crate) fn hash(
     root: &Path,
     md5sum: bool,
-    piece_length: u64,
+    piece_length: u32,
   ) -> Result<(Mode, Vec<u8>), Error> {
-    Hasher::new(md5sum, piece_length).hash_root(root)
+    Self::new(md5sum, piece_length).hash_root(root)
   }
 
-  fn new(md5sum: bool, piece_length: u64) -> Hasher {
-    Hasher {
-      buffer: vec![0; piece_length as usize],
+  fn new(md5sum: bool, piece_length: u32) -> Self {
+    Self {
+      buffer: vec![0; piece_length.into_usize()],
       length: 0,
       piece_bytes_hashed: 0,
       pieces: Vec::new(),
@@ -100,7 +100,10 @@ impl Hasher {
     };
 
     while remaining > 0 {
-      let to_buffer = self.buffer.len().min(remaining as usize);
+      let to_buffer: usize = remaining
+        .min(self.buffer.len().into_u64())
+        .try_into()
+        .unwrap();
       let buffer = &mut self.buffer[0..to_buffer];
 
       file.read_exact(buffer)?;
@@ -110,7 +113,7 @@ impl Hasher {
 
         self.piece_bytes_hashed += 1;
 
-        if self.piece_bytes_hashed == self.piece_length {
+        if self.piece_bytes_hashed == self.piece_length.into() {
           self.pieces.extend(&self.sha1.digest().bytes());
           self.sha1.reset();
           self.piece_bytes_hashed = 0;
diff --git a/src/info.rs b/src/info.rs
index 826efd3..bd80a9a 100644
--- a/src/info.rs
+++ b/src/info.rs
@@ -4,7 +4,7 @@ use crate::common::*;
 pub struct Info {
   pub private: u8,
   #[serde(rename = "piece length")]
-  pub piece_length: u64,
+  pub piece_length: u32,
   pub name: String,
   #[serde(with = "serde_bytes")]
   pub pieces: Vec<u8>,
diff --git a/src/into_u64.rs b/src/into_u64.rs
new file mode 100644
index 0000000..a4e45e9
--- /dev/null
+++ b/src/into_u64.rs
@@ -0,0 +1,16 @@
+use crate::common::*;
+
+// Systems with pointers larger than 64 bits may eventually exist, but
+// for now let's assume that usize is at most 32 bits, and document that
+// assumption with this assert.
+const_assert!(std::mem::size_of::<usize>() <= std::mem::size_of::<u64>());
+
+pub(crate) trait IntoU64 {
+  fn into_u64(self) -> u64;
+}
+
+impl IntoU64 for usize {
+  fn into_u64(self) -> u64 {
+    self as u64
+  }
+}
diff --git a/src/into_usize.rs b/src/into_usize.rs
new file mode 100644
index 0000000..de9859a
--- /dev/null
+++ b/src/into_usize.rs
@@ -0,0 +1,16 @@
+use crate::common::*;
+
+// Intermodal, or at least parts of it, might eventually be ported to
+// 16-bit systems, but for now let's assume that usize is at least 32
+// bits, and document that assumption with this assert.
+const_assert!(std::mem::size_of::<usize>() >= std::mem::size_of::<u32>());
+
+pub(crate) trait IntoUsize {
+  fn into_usize(self) -> usize;
+}
+
+impl IntoUsize for u32 {
+  fn into_usize(self) -> usize {
+    self as usize
+  }
+}
diff --git a/src/main.rs b/src/main.rs
index 738fb97..1c62eef 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,9 +1,29 @@
+#![deny(clippy::all, clippy::pedantic, clippy::restriction)]
+#![allow(
+  clippy::else_if_without_else,
+  clippy::enum_glob_use,
+  clippy::implicit_return,
+  clippy::indexing_slicing,
+  clippy::integer_arithmetic,
+  clippy::missing_docs_in_private_items,
+  clippy::option_map_unwrap_or_else,
+  clippy::option_unwrap_used,
+  clippy::result_expect_used,
+  clippy::result_unwrap_used
+)]
+
 use crate::common::*;
 
 #[cfg(test)]
 #[macro_use]
 mod matches;
 
+#[macro_use]
+mod errln;
+
+#[macro_use]
+mod err;
+
 #[cfg(test)]
 mod testing;
 
@@ -15,6 +35,8 @@ mod error;
 mod file_info;
 mod hasher;
 mod info;
+mod into_u64;
+mod into_usize;
 mod metainfo;
 mod mode;
 mod opt;
diff --git a/src/opt.rs b/src/opt.rs
index f0be0c6..60a6b7c 100644
--- a/src/opt.rs
+++ b/src/opt.rs
@@ -9,7 +9,7 @@ pub(crate) struct Opt {
 }
 
 impl Opt {
-  pub(crate) fn run(self, env: &Environment) -> Result<(), Error> {
+  pub(crate) fn run(self, env: &mut Environment) -> Result<(), Error> {
     self.subcommand.run(env, self.unstable)
   }
 }
diff --git a/src/reckoner.rs b/src/reckoner.rs
index 02997b7..88355f4 100644
--- a/src/reckoner.rs
+++ b/src/reckoner.rs
@@ -11,7 +11,7 @@ pub(crate) trait Reckoner<K> {
   where
     I: IntoIterator<Item = K>,
   {
-    for k in i.into_iter() {
+    for k in i {
       self.increment(k);
     }
   }
diff --git a/src/subcommand.rs b/src/subcommand.rs
index c27f42b..62cb32a 100644
--- a/src/subcommand.rs
+++ b/src/subcommand.rs
@@ -6,7 +6,7 @@ pub(crate) enum Subcommand {
 }
 
 impl Subcommand {
-  pub(crate) fn run(self, env: &Environment, unstable: bool) -> Result<(), Error> {
+  pub(crate) fn run(self, env: &mut Environment, unstable: bool) -> Result<(), Error> {
     match self {
       Self::Torrent(torrent) => torrent.run(env, unstable),
     }
diff --git a/src/torrent.rs b/src/torrent.rs
index 4538437..ad05fbd 100644
--- a/src/torrent.rs
+++ b/src/torrent.rs
@@ -10,7 +10,7 @@ pub(crate) enum Torrent {
 }
 
 impl Torrent {
-  pub(crate) fn run(self, env: &Environment, unstable: bool) -> Result<(), Error> {
+  pub(crate) fn run(self, env: &mut Environment, unstable: bool) -> Result<(), Error> {
     match self {
       Self::Create(create) => create.run(env),
       Self::Stats(stats) => stats.run(env, unstable),
diff --git a/src/torrent/create.rs b/src/torrent/create.rs
index 6cc5598..3a9477a 100644
--- a/src/torrent/create.rs
+++ b/src/torrent/create.rs
@@ -15,7 +15,7 @@ pub(crate) struct Create {
   #[structopt(name = "COMMENT", long = "comment")]
   comment: Option<String>,
   #[structopt(name = "PIECE-LENGTH", long = "piece-length", default_value = "524288")]
-  piece_length: u64,
+  piece_length: u32,
   #[structopt(name = "ANNOUNCE", long = "announce", required(true))]
   announce: Vec<String>,
   #[structopt(name = "MD5SUM", long = "md5sum")]
@@ -31,7 +31,7 @@ impl Create {
     let mut announce_list = Vec::new();
     for announce in &self.announce {
       let tier = announce
-        .split(",")
+        .split(',')
         .map(str::to_string)
         .collect::<Vec<String>>();
 
@@ -104,7 +104,7 @@ impl Create {
     };
 
     let metainfo = Metainfo {
-      comment: self.comment.clone(),
+      comment: self.comment,
       encoding: consts::ENCODING_UTF8.to_string(),
       announce,
       announce_list,
@@ -131,19 +131,19 @@ mod tests {
 
   #[test]
   fn require_input_argument() {
-    let env = environment(&[]);
+    let mut env = environment(&[]);
     assert!(matches!(env.run(), Err(Error::Clap { .. })));
   }
 
   #[test]
   fn require_input_present() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     assert!(matches!(env.run(), Err(Error::Filesystem { .. })));
   }
 
   #[test]
   fn torrent_file_is_bencode_dict() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
@@ -154,7 +154,7 @@ mod tests {
 
   #[test]
   fn privacy_defaults_to_false() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
@@ -165,7 +165,7 @@ mod tests {
 
   #[test]
   fn privacy_flag_sets_privacy() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar", "--private"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar", "--private"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
@@ -176,14 +176,14 @@ mod tests {
 
   #[test]
   fn tracker_flag_must_be_url() {
-    let env = environment(&["--input", "foo", "--announce", "bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     assert!(matches!(env.run(), Err(Error::AnnounceUrlParse { .. })));
   }
 
   #[test]
   fn announce_single() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
@@ -195,7 +195,7 @@ mod tests {
 
   #[test]
   fn announce_single_tier() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar,http://baz"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar,http://baz"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
@@ -210,7 +210,7 @@ mod tests {
 
   #[test]
   fn announce_multiple_tiers() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo",
       "--announce",
@@ -235,7 +235,7 @@ mod tests {
 
   #[test]
   fn comment_default() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
@@ -246,7 +246,7 @@ mod tests {
 
   #[test]
   fn comment_set() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo",
       "--announce",
@@ -264,18 +264,18 @@ mod tests {
 
   #[test]
   fn piece_length_default() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
     let bytes = fs::read(torrent).unwrap();
     let metainfo = serde_bencode::de::from_bytes::<Metainfo>(&bytes).unwrap();
-    assert_eq!(metainfo.info.piece_length, 512 * 2u64.pow(10));
+    assert_eq!(metainfo.info.piece_length, 512 * 2u32.pow(10));
   }
 
   #[test]
   fn piece_length_override() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo",
       "--announce",
@@ -293,7 +293,7 @@ mod tests {
 
   #[test]
   fn name() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo",
       "--announce",
@@ -311,7 +311,7 @@ mod tests {
 
   #[test]
   fn name_subdir() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo/bar",
       "--announce",
@@ -331,7 +331,7 @@ mod tests {
 
   #[test]
   fn destination_override() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo",
       "--output",
@@ -348,7 +348,7 @@ mod tests {
 
   #[test]
   fn created_by_default() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
@@ -359,7 +359,7 @@ mod tests {
 
   #[test]
   fn created_by_unset() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo",
       "--announce",
@@ -376,7 +376,7 @@ mod tests {
 
   #[test]
   fn encoding() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     env.run().unwrap();
     let torrent = env.resolve("foo.torrent");
@@ -387,7 +387,7 @@ mod tests {
 
   #[test]
   fn created_date_default() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     fs::write(env.resolve("foo"), "").unwrap();
     let now = SystemTime::now()
       .duration_since(SystemTime::UNIX_EPOCH)
@@ -403,7 +403,7 @@ mod tests {
 
   #[test]
   fn created_date_unset() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo",
       "--announce",
@@ -420,7 +420,7 @@ mod tests {
 
   #[test]
   fn single_small() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     let contents = "bar";
     fs::write(env.resolve("foo"), contents).unwrap();
     env.run().unwrap();
@@ -439,7 +439,7 @@ mod tests {
 
   #[test]
   fn single_one_byte_piece() {
-    let env = environment(&[
+    let mut env = environment(&[
       "--input",
       "foo",
       "--announce",
@@ -474,7 +474,7 @@ mod tests {
 
   #[test]
   fn single_empty() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     let contents = "";
     fs::write(env.resolve("foo"), contents).unwrap();
     env.run().unwrap();
@@ -493,7 +493,7 @@ mod tests {
 
   #[test]
   fn multiple_no_files() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     let dir = env.resolve("foo");
     fs::create_dir(&dir).unwrap();
     env.run().unwrap();
@@ -506,7 +506,7 @@ mod tests {
 
   #[test]
   fn multiple_one_file() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     let dir = env.resolve("foo");
     fs::create_dir(&dir).unwrap();
     let file = dir.join("bar");
@@ -522,7 +522,7 @@ mod tests {
 
   #[test]
   fn multiple_three_files() {
-    let env = environment(&["--input", "foo", "--announce", "http://bar"]);
+    let mut env = environment(&["--input", "foo", "--announce", "http://bar"]);
     let dir = env.resolve("foo");
     fs::create_dir(&dir).unwrap();
     fs::write(dir.join("a"), "abc").unwrap();
diff --git a/src/torrent/stats.rs b/src/torrent/stats.rs
index b81e808..411011c 100644
--- a/src/torrent/stats.rs
+++ b/src/torrent/stats.rs
@@ -11,7 +11,7 @@ pub(crate) struct Stats {
 }
 
 impl Stats {
-  pub(crate) fn run(self, env: &Environment, unstable: bool) -> Result<(), Error> {
+  pub(crate) fn run(self, env: &mut Environment, unstable: bool) -> Result<(), Error> {
     if !unstable {
       return Err(Error::Unstable {
         feature: "torrent stats subcommand",
@@ -23,7 +23,7 @@ impl Stats {
     let mut extractor = Extractor::new(&self.extract_patterns);
 
     for result in WalkDir::new(path).sort_by(|a, b| a.file_name().cmp(b.file_name())) {
-      if extractor.torrents >= self.limit.unwrap_or(u64::MAX) {
+      if extractor.torrents >= self.limit.unwrap_or(u64::max_value()) {
         break;
       }
 
@@ -32,25 +32,29 @@ impl Stats {
       extractor.process(entry.path());
     }
 
-    println!("Torrents processed: {}", extractor.torrents);
-    println!("Read failed:        {}", extractor.io_errors);
-    println!("Decode failed:      {}", extractor.bencode_decode_errors);
+    errln!(env, "Torrents processed: {}", extractor.torrents);
+    errln!(env, "Read failed:        {}", extractor.io_errors);
+    errln!(
+      env,
+      "Decode failed:      {}",
+      extractor.bencode_decode_errors
+    );
 
     let mut paths = extractor.paths.into_iter().collect::<Vec<(String, u64)>>();
     paths.sort_by_key(|(_, count)| Reverse(*count));
     let max = paths.iter().map(|(_, count)| *count).max().unwrap_or(0);
     let width = max.to_string().len();
 
-    println!("Keys:");
+    errln!(env, "Keys:");
     for (key, count) in &paths {
       if key.starts_with("info/files") {
         continue;
       }
-      println!("{:<width$} - {}", count, key, width = width);
+      errln!(env, "{:<width$} - {}", count, key, width = width);
     }
     for (key, count) in paths {
       if key.starts_with("info/files") {
-        println!("{:<width$} - {}", count, key, width = width);
+        errln!(env, "{:<width$} - {}", count, key, width = width);
       }
     }
 
@@ -60,15 +64,16 @@ impl Stats {
         .into_iter()
         .collect::<Vec<(String, Vec<String>)>>();
 
-      println!("Values:");
+      errln!(env, "Values:");
       for (pattern, values) in values {
-        println!("{}: ", pattern);
+        err!(env, "{}: ", pattern);
         for (i, value) in values.iter().enumerate() {
           if i > 0 {
-            print!(", ");
+            err!(env, ", ");
           }
-          print!("{}", value);
+          err!(env, "{}", value);
         }
+        errln!(env)
       }
     }
 
@@ -87,10 +92,11 @@ struct Extractor {
 }
 
 impl Extractor {
-  fn new(regexes: &[Regex]) -> Extractor {
-    let regex_set = RegexSet::new(regexes.iter().map(Regex::as_str)).unwrap();
+  fn new(regexes: &[Regex]) -> Self {
+    let regex_set = RegexSet::new(regexes.iter().map(Regex::as_str))
+      .expect("Validated regex pattern failed to recompile in regex set");
 
-    Extractor {
+    Self {
       bencode_decode_errors: 0,
       io_errors: 0,
       paths: HashMap::new(),
@@ -112,20 +118,18 @@ impl Extractor {
 
     self.torrents += 1;
 
-    let contents = match fs::read(&path) {
-      Ok(contents) => contents,
-      Err(_) => {
-        self.io_errors += 1;
-        return;
-      }
+    let contents = if let Ok(contents) = fs::read(&path) {
+      contents
+    } else {
+      self.io_errors += 1;
+      return;
     };
 
-    let value = match bencode::Value::decode(&contents) {
-      Ok(value) => value,
-      Err(_) => {
-        self.bencode_decode_errors += 1;
-        return;
-      }
+    let value = if let Ok(value) = bencode::Value::decode(&contents) {
+      value
+    } else {
+      self.bencode_decode_errors += 1;
+      return;
     };
 
     self.extract(&value);