Switch to using a type for bracket depth.

This is to make changing the type easier in the future.

src/parser/org_source.rs

@@ -11,15 +11,17 @@ use nom::Slice;
 use crate::error::CustomError;
 use crate::error::MyError;
 
+pub type BracketDepth = i16;
+
 #[derive(Copy, Clone)]
 pub struct OrgSource<'s> {
     full_source: &'s str,
     start: usize,
     end: usize, // exclusive
     start_of_line: usize,
-    bracket_depth: i16,     // []
-    brace_depth: i16,       // {}
-    parenthesis_depth: i16, // ()
+    bracket_depth: BracketDepth,     // []
+    brace_depth: BracketDepth,       // {}
+    parenthesis_depth: BracketDepth, // ()
     preceding_character: Option<char>,
 }
 
@@ -71,15 +73,15 @@ impl<'s> OrgSource<'s> {
         self.slice(..(other.start - self.start))
     }
 
-    pub fn get_bracket_depth(&self) -> i16 {
+    pub fn get_bracket_depth(&self) -> BracketDepth {
         self.bracket_depth
     }
 
-    pub fn get_brace_depth(&self) -> i16 {
+    pub fn get_brace_depth(&self) -> BracketDepth {
         self.brace_depth
     }
 
-    pub fn get_parenthesis_depth(&self) -> i16 {
+    pub fn get_parenthesis_depth(&self) -> BracketDepth {
         self.parenthesis_depth
     }
 }