diff --git a/src/ini_file.mbt b/src/ini_file.mbt
index c303397..a6d4aca 100644
--- a/src/ini_file.mbt
+++ b/src/ini_file.mbt
@@ -12,20 +12,20 @@ priv struct Value(String) derive(Show)
 
 ///|
 struct IniFile {
-  sections : @hashmap.T[Section, @hashmap.T[Key, Value]]
+  sections : @hashmap.HashMap[Section, @hashmap.HashMap[Key, Value]]
   // default not case sensitive
   is_case_sensitive : Bool
 }
 
 ///|
-pub fn IniFile::new(is_case_sensitive~ : Bool = false) -> IniFile {
+pub fn IniFile::new(is_case_sensitive? : Bool = false) -> IniFile {
   IniFile::{ sections: @hashmap.new(), is_case_sensitive }
 }
 
 ///|
 fn IniFile::new_with_sections(
-  sections : @hashmap.T[Section, @hashmap.T[Key, Value]],
-  is_case_sensitive~ : Bool = false,
+  sections : @hashmap.HashMap[Section, @hashmap.HashMap[Key, Value]],
+  is_case_sensitive? : Bool = false,
 ) -> IniFile {
   IniFile::{ sections, is_case_sensitive }
 }
@@ -39,10 +39,11 @@ fn IniFile::lower_if_needed(self : IniFile, s : String) -> String {
   }
 }
 
-///| get is a alias for get_string
+///|
+/// get is a alias for get_string
 pub fn IniFile::get(
   self : IniFile,
-  section~ : String = "",
+  section? : String = "",
   key : String,
 ) -> String? {
   self.get_string(section~, key)
@@ -51,7 +52,7 @@ pub fn IniFile::get(
 ///|
 pub fn IniFile::get_string(
   self : IniFile,
-  section~ : String = "",
+  section? : String = "",
   key : String,
 ) -> String? {
   let section_map = self.get_section(
@@ -61,10 +62,10 @@ pub fn IniFile::get_string(
     },
     create_if_not_exists=false,
   )
-  guard not(section_map.is_empty()) else { None }
+  guard section_map is Some(_) else { None }
   let section_map = section_map.unwrap()
   let value = section_map.get(self.lower_if_needed(key))
-  guard not(value.is_empty()) else { None }
+  guard value is Some(_) else { None }
   let value = value.unwrap()
   let Value(v) = value
   Some(v)
@@ -73,11 +74,11 @@ pub fn IniFile::get_string(
 ///|
 pub fn IniFile::get_bool(
   self : IniFile,
-  section~ : String = "",
+  section? : String = "",
   key : String,
 ) -> Bool? {
   let value = self.get_string(section~, key)
-  guard not(value.is_empty()) else { None }
+  guard value is Some(_) else { None }
   let value = value.unwrap()
   match value.to_lower() {
     "true" | "yes" | "on" => Some(true)
@@ -92,8 +93,8 @@ pub fn IniFile::get_bool(
 fn IniFile::get_section(
   self : IniFile,
   section : Section,
-  create_if_not_exists~ : Bool = false,
-) -> @hashmap.T[Key, Value]? {
+  create_if_not_exists? : Bool = false,
+) -> @hashmap.HashMap[Key, Value]? {
   let section_map = self.sections.get(section)
   match section_map {
     None =>
@@ -112,7 +113,7 @@ fn IniFile::get_section(
 fn IniFile::get_section_or_create(
   self : IniFile,
   section : Section,
-) -> @hashmap.T[Key, Value] {
+) -> @hashmap.HashMap[Key, Value] {
   let section_map = self.get_section(section, create_if_not_exists=true)
   section_map.unwrap()
 }
@@ -120,7 +121,7 @@ fn IniFile::get_section_or_create(
 ///|
 pub fn IniFile::set(
   self : IniFile,
-  section~ : String = "",
+  section? : String = "",
   key : String,
   value : String,
 ) -> Unit {
@@ -133,7 +134,8 @@ pub fn IniFile::set(
   section_map.set(self.lower_if_needed(key), Value(value))
 }
 
-///| Converts the IniFile to a standard INI format string
+///|
+/// Converts the IniFile to a standard INI format string
 pub fn IniFile::to_string(self : IniFile) -> String {
   fn escape_char(c : Char) -> String {
     match c {
@@ -176,7 +178,7 @@ pub fn IniFile::to_string(self : IniFile) -> String {
   let buf = StringBuilder::new()
   // Global section first
   let global_section = self.sections.get(Section::Global)
-  if not(global_section.is_empty()) {
+  if global_section is Some(_) {
     global_section
     .unwrap()
     .iter()
diff --git a/src/parser.mbt b/src/parser.mbt
index 4e14fe1..a3a587c 100644
--- a/src/parser.mbt
+++ b/src/parser.mbt
@@ -11,7 +11,7 @@ pub suberror IniParseError {
 ///|
 priv struct ParseContext {
   mut current_section : Section
-  sections : @hashmap.T[Section, @hashmap.T[Key, Value]]
+  sections : @hashmap.HashMap[Section, @hashmap.HashMap[Key, Value]]
   mut line : Int
   mut col : Int
   mut key : String
@@ -66,7 +66,7 @@ fn IniParseState::lower_if_needed(self : IniParseState, s : String) -> String {
 }
 
 ///|
-pub fn IniParseState::new(is_case_sensitive~ : Bool = false) -> IniParseState {
+pub fn IniParseState::new(is_case_sensitive? : Bool = false) -> IniParseState {
   IniParseState::{
     ctx: ParseContext::{
       current_section: Section::Global,
@@ -86,7 +86,7 @@ pub fn IniParseState::new(is_case_sensitive~ : Bool = false) -> IniParseState {
 ///|
 pub fn parse(
   str : String,
-  is_case_sensitive~ : Bool = false,
+  is_case_sensitive? : Bool = false,
 ) -> IniFile raise IniParseError {
   IniParseState::new(is_case_sensitive~).parse(str).finish()
 }
@@ -405,11 +405,11 @@ fn IniParseState::commit_value(
   self : IniParseState,
   // If true, drop the last space in the value
   // this is used to handle the case when a comment is at the end of the line
-  drop_last_one_space~ : Bool = false,
+  drop_last_one_space? : Bool = false,
 ) -> IniParseState raise IniParseError {
   let mut value = self.ctx.buffer.to_string()
-  if drop_last_one_space && value.rev_iter().nth(0).unwrap().is_whitespace() {
-    value = value.substring(end=value.length() - 1)
+  if drop_last_one_space && value is [.. rest, ch] && ch.is_whitespace() {
+    value = rest.to_string()
   }
   let section = self.ctx.sections.get(self.ctx.current_section).unwrap()
   let key = self.ctx.key
@@ -500,7 +500,7 @@ test "IniParseState::process_char/global_section_edge_cases" {
 }
 
 ///|
-test "panic IniParseState::process_char/unclosed_section" {
+test "panic IniParseState::process_char/unclosed_section_newline" {
   let state = IniParseState::new()
   ignore(state.process_char('['))
   ignore(state.process_char('\n'))
@@ -649,7 +649,7 @@ test "IniParseState::handle_key_char/valueless_key" {
   inspect(state.ctx.key, content="key")
   inspect(state.phase, content="Start")
   let section = state.ctx.sections.get(state.ctx.current_section)
-  inspect(section.is_empty(), content="false")
+  inspect(section is Some(_), content="true")
   let value = section.unwrap().get("key")
   inspect(value, content="Some(Value(\"\"))")
 }
@@ -732,10 +732,10 @@ test "IniParseState::commit_value/basic" {
   inspect(state.ctx.buffer.is_empty(), content="true")
   // Verify the section exists
   let section = state.ctx.sections.get(Section::NamedSection("section"))
-  inspect(section.is_empty(), content="false")
+  inspect(section is Some(_), content="true")
   // Verify the key exists in the section
   let value = section.unwrap().get("key")
-  inspect(value.is_empty(), content="false")
+  inspect(value is Some(_), content="true")
 }
 
 ///|
@@ -752,8 +752,8 @@ test "IniParseState::commit_value/empty_value" {
   let state = state.commit_value()
   // Verify the section exists
   let section = state.ctx.sections.get(Section::NamedSection("section"))
-  inspect(section.is_empty(), content="false")
+  inspect(section is Some(_), content="true")
   // Verify the key exists in the section with empty value
   let value = section.unwrap().get("key")
-  inspect(value.is_empty(), content="false")
+  inspect(value is Some(_), content="true")
 }
diff --git a/src/parser_test.mbt b/src/parser_test.mbt
index cf4cb54..858da8b 100644
--- a/src/parser_test.mbt
+++ b/src/parser_test.mbt
@@ -128,9 +128,10 @@ test "parse/error_value_without_section_or_key" {
   // This case is tricky because the parser might interpret 'value' as a key
   // Let's test assignment without a preceding key
   let input = "[section]\n=value"
-  match (try? parse(input)) {
-    Ok(_) => assert_true(false)
-    Err(_) => assert_true(true)
+  try parse(input) catch {
+    _ => assert_true(true)
+  } noraise {
+    _ => assert_true(false)
   }
   // The ValueWithoutSection error is harder to trigger directly with current logic,
   // as '=' is required to start reading a value, which implies a key was being read.
diff --git a/src/pkg.generated.mbti b/src/pkg.generated.mbti
new file mode 100644
index 0000000..5d653c3
--- /dev/null
+++ b/src/pkg.generated.mbti
@@ -0,0 +1,34 @@
+// Generated using `moon info`, DON'T EDIT IT
+package "ShellWen/sw_ini"
+
+// Values
+pub fn parse(String, is_case_sensitive? : Bool) -> IniFile raise IniParseError
+
+// Errors
+pub suberror IniParseError {
+  UnexpectedEqualSign(line~ : Int, col~ : Int)
+  EmptySection(line~ : Int, col~ : Int)
+  UnclosedSection(line~ : Int, col~ : Int)
+  ValueWithoutSection(line~ : Int, col~ : Int)
+  QuoteMismatch(line~ : Int, col~ : Int)
+  QuoteNotClosed(line~ : Int, col~ : Int)
+}
+
+// Types and methods
+type IniFile
+pub fn IniFile::get(Self, section? : String, String) -> String?
+pub fn IniFile::get_bool(Self, section? : String, String) -> Bool?
+pub fn IniFile::get_string(Self, section? : String, String) -> String?
+pub fn IniFile::new(is_case_sensitive? : Bool) -> Self
+pub fn IniFile::set(Self, section? : String, String, String) -> Unit
+pub fn IniFile::to_string(Self) -> String
+
+type IniParseState
+pub fn IniParseState::finish(Self) -> IniFile raise IniParseError
+pub fn IniParseState::new(is_case_sensitive? : Bool) -> Self
+pub fn IniParseState::parse(Self, String) -> Self raise IniParseError
+
+// Type aliases
+
+// Traits
+