diff --git a/Cargo.toml b/Cargo.toml
index 85c393f..d3e9f23 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ license = "MIT OR Apache-2.0" # Same as rustc
 repository = "https://github.com/Manishearth/compiletest-rs"
 keywords = ["compiletest", "test", "plugin"]
 readme = "README.md"
+edition = "2021"
 
 [lib]
 name = "compiletest_rs"
diff --git a/src/common.rs b/src/common.rs
index 5d42633..d362fbd 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -17,8 +17,8 @@ use std::path::Path;
 use std::path::PathBuf;
 use std::str::FromStr;
 
-use runtest::dylib_env_var;
-use test::ColorConfig;
+use crate::runtest::dylib_env_var;
+use crate::test::ColorConfig;
 
 #[derive(Clone, Copy, PartialEq, Debug)]
 pub enum Mode {
diff --git a/src/header.rs b/src/header.rs
index d490a0d..267688a 100644
--- a/src/header.rs
+++ b/src/header.rs
@@ -14,11 +14,11 @@ use std::io::prelude::*;
 use std::io::BufReader;
 use std::path::{Path, PathBuf};
 
-use common;
-use common::Config;
-use util;
+use crate::common;
+use crate::common::Config;
+use crate::util;
 
-use extract_gdb_version;
+use crate::extract_gdb_version;
 
 /// Properties which must be known very early, before actually running
 /// the test.
diff --git a/src/json.rs b/src/json.rs
index 58f4f9c..1716635 100644
--- a/src/json.rs
+++ b/src/json.rs
@@ -8,8 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use errors::{Error, ErrorKind};
-use runtest::ProcRes;
+use crate::errors::{Error, ErrorKind};
+use crate::runtest::ProcRes;
 use std::path::Path;
 use std::str::FromStr;
 
@@ -236,7 +236,7 @@ fn push_expected_errors(
 
     // Add notes for the backtrace
     for span in primary_spans {
-        for frame in &span.expansion {
+        if let Some(frame) = &span.expansion {
             push_backtrace(expected_errors, frame, file_name);
         }
     }
@@ -272,7 +272,7 @@ fn push_backtrace(
         });
     }
 
-    for previous_expansion in &expansion.span.expansion {
+    if let Some(previous_expansion) = &expansion.span.expansion {
         push_backtrace(expected_errors, previous_expansion, file_name);
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index 8489453..b0045cc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -38,8 +38,8 @@ extern crate serde_json;
 extern crate serde_derive;
 extern crate rustfix;
 
-use common::{DebugInfoGdb, DebugInfoLldb, Pretty};
-use common::{Mode, TestPaths};
+use crate::common::{DebugInfoGdb, DebugInfoLldb, Pretty};
+use crate::common::{Mode, TestPaths};
 use std::env;
 use std::ffi::OsString;
 use std::fs;
@@ -57,7 +57,7 @@ pub mod runtest;
 pub mod uidiff;
 pub mod util;
 
-pub use common::Config;
+pub use crate::common::Config;
 
 pub fn run_tests(config: &Config) {
     if config.target.contains("android") {
diff --git a/src/read2.rs b/src/read2.rs
index c3af44a..715ea86 100644
--- a/src/read2.rs
+++ b/src/read2.rs
@@ -21,7 +21,7 @@ mod imp {
     pub fn read2(
         out_pipe: ChildStdout,
         err_pipe: ChildStderr,
-        data: &mut FnMut(bool, &mut Vec<u8>, bool),
+        data: &mut dyn FnMut(bool, &mut Vec<u8>, bool),
     ) -> io::Result<()> {
         let mut buffer = Vec::new();
         out_pipe.read_to_end(&mut buffer)?;
@@ -129,7 +129,7 @@ mod imp {
     pub fn read2(
         out_pipe: ChildStdout,
         err_pipe: ChildStderr,
-        data: &mut FnMut(bool, &mut Vec<u8>, bool),
+        data: &mut dyn FnMut(bool, &mut Vec<u8>, bool),
     ) -> io::Result<()> {
         let mut out = Vec::new();
         let mut err = Vec::new();
diff --git a/src/runtest.rs b/src/runtest.rs
index d153fcd..2eeca4f 100644
--- a/src/runtest.rs
+++ b/src/runtest.rs
@@ -8,16 +8,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use crate::common::{expected_output_path, UI_FIXED, UI_STDERR, UI_STDOUT};
+use crate::common::{Assembly, Incremental, MirOpt, RunMake, Ui};
+use crate::common::{Codegen, CodegenUnits, DebugInfoGdb, DebugInfoLldb, Rustdoc};
+use crate::common::{CompileFail, ParseFail, Pretty, RunFail, RunPass, RunPassValgrind};
+use crate::common::{Config, TestPaths};
+use crate::errors::{self, Error, ErrorKind};
+use crate::header::TestProps;
+use crate::json;
 use crate::util::{logv, PathBufExt};
-use common::{expected_output_path, UI_FIXED, UI_STDERR, UI_STDOUT};
-use common::{Assembly, Incremental, MirOpt, RunMake, Ui};
-use common::{Codegen, CodegenUnits, DebugInfoGdb, DebugInfoLldb, Rustdoc};
-use common::{CompileFail, ParseFail, Pretty, RunFail, RunPass, RunPassValgrind};
-use common::{Config, TestPaths};
-use errors::{self, Error, ErrorKind};
 use filetime::FileTime;
-use header::TestProps;
-use json;
 use regex::Regex;
 use rustfix::{apply_suggestions, get_suggestions_from_json, Filter};
 
@@ -34,7 +34,7 @@ use std::process::{Child, Command, ExitStatus, Output, Stdio};
 use std::str;
 use std::sync::{Arc, Mutex, RwLock};
 
-use extract_gdb_version;
+use crate::extract_gdb_version;
 
 fn get_or_create_coverage_file(path: &Path, create: impl FnOnce() -> File) -> Arc<Mutex<File>> {
     lazy_static::lazy_static! {
@@ -115,7 +115,7 @@ pub fn run(config: Config, testpaths: &TestPaths) {
 
     base_cx.complete_all();
 
-    File::create(::stamp(&config, testpaths)).unwrap();
+    File::create(crate::stamp(&config, testpaths)).unwrap();
 }
 
 struct TestCx<'test> {
@@ -1707,7 +1707,7 @@ actual:\n\
     }
 
     fn make_cmdline(&self, command: &Command, libpath: &str) -> String {
-        use util;
+        use crate::util;
 
         // Linux and mac don't require adjusting the library search path
         if cfg!(unix) {
@@ -1940,9 +1940,7 @@ actual:\n\
 
     fn charset() -> &'static str {
         // FreeBSD 10.1 defaults to GDB 6.1.1 which doesn't support "auto" charset
-        if cfg!(target_os = "bitrig") {
-            "auto"
-        } else if cfg!(target_os = "freebsd") {
+        if cfg!(target_os = "freebsd") {
             "ISO-8859-1"
         } else {
             "UTF-8"
@@ -3067,7 +3065,7 @@ fn nocomment_mir_line(line: &str) -> &str {
 }
 
 fn read2_abbreviated(mut child: Child) -> io::Result<Output> {
-    use read2::read2;
+    use crate::read2::read2;
     use std::mem::replace;
 
     const HEAD_LEN: usize = 160 * 1024;
@@ -3142,8 +3140,8 @@ fn read2_abbreviated(mut child: Child) -> io::Result<Output> {
     read2(
         child.stdout.take().unwrap(),
         child.stderr.take().unwrap(),
-        &mut |is_stdout, data, _| {
-            if is_stdout { &mut stdout } else { &mut stderr }.extend(data);
+        &mut |is_stdout, data: &mut Vec<u8>, _| {
+            if is_stdout { &mut stdout } else { &mut stderr }.extend(&data);
             data.clear();
         },
     )?;
diff --git a/src/util.rs b/src/util.rs
index 08a27fc..0773f11 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use common::Config;
+use crate::common::Config;
 use std::env;
 use std::ffi::OsStr;
 use std::path::PathBuf;
diff --git a/tests/bless.rs b/tests/bless.rs
index 3e5b2b4..1c161d8 100644
--- a/tests/bless.rs
+++ b/tests/bless.rs
@@ -3,8 +3,8 @@
 extern crate compiletest_rs as compiletest;
 
 mod test_support;
-use compiletest::Config;
-use test_support::{testsuite, TestsuiteBuilder, GLOBAL_ROOT};
+use crate::compiletest::Config;
+use crate::test_support::{testsuite, TestsuiteBuilder, GLOBAL_ROOT};
 
 fn setup(mode: &str) -> (Config, TestsuiteBuilder) {
     let builder = testsuite(mode);