bump MSRV to 1.70.0 (#8877)

* rust-toolchain.toml: bump MSRV to 1.70.0

With Firefox 120 released on 21 November 2023, the MSRV is now 1.70.0.

* Fix cargo fmt with Rust 1.70.0

* Fix cargo clippy with Rust 1.70.0

* Fix cargo doc with Rust 1.70.0

* rust-toolchain.toml: add clippy component

* .github: bump dtolnay/rust-toolchain to 1.70

* helix-term: bump rust-version to 1.70

* helix-view/gutter: use checked_ilog10 to count digits

* helix-core/syntax: use MAIN_SEPARATOR_STR constant

* helix-view/handlers/dap: use Display impl for displaying process spawn error

* WIP: helix-term/commands: use checked math to assert ranges cannot overlap

3 files changed, 5 insertions, 13 deletions

diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index 7af28ccc..5a81cb5d 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -727,7 +727,7 @@ pub struct WhitespaceCharacters {
 impl Default for WhitespaceCharacters {
     fn default() -> Self {
         Self {
-            space: '·',    // U+00B7
+            space: '·',   // U+00B7
             nbsp: '⍽',    // U+237D
             tab: '→',     // U+2192
             newline: '⏎', // U+23CE
@@ -755,12 +755,13 @@ impl Default for IndentGuidesConfig {
 }
 
 /// Line ending configuration.
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Default, Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(rename_all = "lowercase")]
 pub enum LineEndingConfig {
     /// The platform's native line ending.
     ///
     /// `crlf` on Windows, otherwise `lf`.
+    #[default]
     Native,
     /// Line feed.
     LF,
@@ -777,12 +778,6 @@ pub enum LineEndingConfig {
     Nel,
 }
 
-impl Default for LineEndingConfig {
-    fn default() -> Self {
-        LineEndingConfig::Native
-    }
-}
-
 impl From<LineEndingConfig> for LineEnding {
     fn from(line_ending: LineEndingConfig) -> Self {
         match line_ending {
diff --git a/helix-view/src/gutter.rs b/helix-view/src/gutter.rs
index 397dff4f..ebdac9e2 100644
--- a/helix-view/src/gutter.rs
+++ b/helix-view/src/gutter.rs
@@ -9,8 +9,7 @@ use crate::{
 };
 
 fn count_digits(n: usize) -> usize {
-    // TODO: use checked_log10 when MSRV reaches 1.67
-    std::iter::successors(Some(n), |&n| (n >= 10).then_some(n / 10)).count()
+    (usize::checked_ilog10(n).unwrap_or(0) + 1) as usize
 }
 
 pub type GutterFn<'doc> = Box<dyn FnMut(usize, bool, bool, &mut String) -> Option<Style> + 'doc>;
diff --git a/helix-view/src/handlers/dap.rs b/helix-view/src/handlers/dap.rs
index 3da01494..e1437bef 100644
--- a/helix-view/src/handlers/dap.rs
+++ b/helix-view/src/handlers/dap.rs
@@ -369,9 +369,7 @@ impl Editor {
                     {
                         Ok(process) => process,
                         Err(err) => {
-                            // TODO replace the pretty print {:?} with a regular format {}
-                            // when the MSRV is raised to 1.60.0
-                            self.set_error(format!("Error starting external terminal: {:?}", err));
+                            self.set_error(format!("Error starting external terminal: {}", err));
                             return true;
                         }
                     };