diff --git a/dm_std_lib/std/core/string.dm b/dm_std_lib/std/core/string.dm
index c00552d..9aa2a4f 100644
--- a/dm_std_lib/std/core/string.dm
+++ b/dm_std_lib/std/core/string.dm
@@ -4,5 +4,4 @@ pub int String {
     bytes: Array<Byte>
 }
 
-#[internal]
 impl StringImpl(bytes) : String
diff --git a/src/ast/mod.rs b/src/ast/mod.rs
index 47d810d..257df08 100644
--- a/src/ast/mod.rs
+++ b/src/ast/mod.rs
@@ -24,7 +24,8 @@ pub enum Declaration {
         identifier: Identifier,
         is_extern: bool,
         is_public: bool,
-        type_declaration: TypeDeclaration
+        type_declaration: TypeDeclaration,
+        impl_ctor: Option<ImplCtor>
     },
     Module {
         identifier: Identifier,
@@ -36,8 +37,10 @@ pub enum Declaration {
         identifier: Identifier,
         is_extern: bool,
         is_public: bool,
-        statement: Statement 
-    }
+        statement: Statement
+    },
+    Prop(Prop),
+    Field(Field)
 }
 
 #[derive(Debug)]
@@ -89,6 +92,30 @@ pub struct Type {
     generics: Vec<GenericArgument>
 }
 
+#[derive(Debug)]
+pub struct ImplCtor {
+    args: Vec<ImplCtorArg>
+}
+
+#[derive(Debug)]
+pub struct ImplCtorArg {
+    is_field: bool,
+    identifier: Identifier,
+    r#type: Option<Type>
+}
+
+#[derive(Debug)]
+pub struct Prop {
+    identifier: Identifier,
+    r#type: Type
+}
+
+#[derive(Debug)]
+pub struct Field {
+    identifier: Identifier,
+    r#type: Type
+}
+
 #[derive(Debug)]
 pub enum Statement {
     BlockStatement {
@@ -98,6 +125,59 @@ pub enum Statement {
     AssignmentStatement
 }
 
+fn build_field(field_pair: Pair<Rule>) -> Declaration {
+    todo!()
+}
+
+fn build_prop(prop_pair: Pair<Rule>) -> Declaration {
+    todo!()
+}
+
+fn build_impl_ctor_arg(impl_ctor_arg_pair: Pair<Rule>) -> ImplCtorArg {
+    let mut is_field = false;
+    let mut identifier: Option<Identifier> = None;
+    let mut r#type: Option<Type> = None;
+
+    for pair in impl_ctor_arg_pair.into_inner() {
+        match pair.as_rule() {
+            Rule::fld => {
+                is_field = true;
+            },
+            Rule::identifier => {
+                identifier = Some(build_identifier(pair));
+            },
+            Rule::r#type => {
+                r#type = Some(build_type(pair));
+            },
+            _ => panic!("Unexpected rule: {}", pair)
+        }
+    }
+
+    ImplCtorArg {
+        is_field,
+        identifier: identifier.unwrap(),
+        r#type
+    }
+}
+
+fn build_impl_ctor(impl_ctor_pair: Pair<Rule>) -> ImplCtor {
+    let impl_ctor_args_pair = impl_ctor_pair.into_inner().next().unwrap();
+    let mut args: Vec<ImplCtorArg> = vec![];
+
+    for pair in impl_ctor_args_pair.into_inner() {
+        match pair.as_rule() {
+            Rule::impl_ctor_arg => {
+                args.push(build_impl_ctor_arg(pair));
+            }
+            _ => panic!("Unexpected rule: {}", pair)
+        }
+    }
+
+    ImplCtor {
+        args
+    }
+}
+
 fn build_generic_argument(generic_argument_pair: Pair<Rule>) -> GenericArgument {
     let fqn_pair = generic_argument_pair.into_inner().next().unwrap();
     GenericArgument {
@@ -163,14 +243,14 @@ fn build_generic_parameters_declaration(generic_parameters_declaration_pair: Pai
 
 fn build_extends_list(extends_list_pair: Pair<Rule>) -> Vec<Type> {
     let mut extensions: Vec<Type> = vec![];
-    
+
     for pair in extends_list_pair.into_inner() {
         match pair.as_rule() {
             Rule::r#type => {
-                extensions.push(build_type(pair));            
+                extensions.push(build_type(pair));
             }
             _ => panic!("Expected only type rule. Found: {}", pair)
-        } 
+        }
     }
 
     extensions
@@ -181,7 +261,7 @@ fn build_interface(is_extern: bool, is_public: bool, interface_pair: Pair<Rule>)
     let mut generic_parameters: Option<Vec<GenericParameter>> = None;
     let mut extends: Option<Vec<Type>> = None;
     let mut declarations: Vec<Declaration> = vec![];
-   
+
     for pair in interface_pair.into_inner() {
         match pair.as_rule() {
             Rule::identifier => {
@@ -191,7 +271,7 @@ fn build_interface(is_extern: bool, is_public: bool, interface_pair: Pair<Rule>)
                 generic_parameters = Some(build_generic_parameters_declaration(pair));
             }
             Rule::extends_list => {
-                extends = Some(build_extends_list(pair));    
+                extends = Some(build_extends_list(pair));
             }
             Rule::declaration => {
                 declarations.push(build_declaration(pair));
@@ -203,20 +283,57 @@ fn build_interface(is_extern: bool, is_public: bool, interface_pair: Pair<Rule>)
         }
     }
 
-    Declaration::Interface { 
-        identifier: identifier.unwrap(), 
-        is_extern, 
-        is_public, 
+    Declaration::Interface {
+        identifier: identifier.unwrap(),
+        is_extern,
+        is_public,
         type_declaration: TypeDeclaration::new(
             generic_parameters.unwrap_or(vec![]),
-            extends.unwrap_or(vec![]), 
+            extends.unwrap_or(vec![]),
             declarations
         )
     }
 }
 
-fn build_implementation(is_extern: bool, is_public: bool, pair: Pair<Rule>) -> Declaration {
-    todo!()
+fn build_implementation(is_extern: bool, is_public: bool, implementation_pair: Pair<Rule>) -> Declaration {
+    let mut identifier: Option<Identifier> = None;
+    let mut generic_parameters: Option<Vec<GenericParameter>> = None;
+    let mut impl_ctor: Option<ImplCtor> = None;
+    let mut extends: Option<Vec<Type>> = None;
+    let mut declarations: Vec<Declaration> = vec![];
+
+    for pair in implementation_pair.into_inner() {
+        match pair.as_rule() {
+            Rule::identifier => {
+                identifier = Some(build_identifier(pair));
+            },
+            Rule::generic_parameters_declaration => {
+                generic_parameters = Some(build_generic_parameters_declaration(pair));
+            },
+            Rule::impl_ctor => {
+                impl_ctor = Some(build_impl_ctor(pair));
+            },
+            Rule::extends_list => {
+                extends = Some(build_extends_list(pair));
+            },
+            Rule::declaration => {
+                declarations.push(build_declaration(pair));
+            }
+            _ => panic!("Unexpected rule: {}", pair)
+        }
+    }
+
+    Declaration::Implementation {
+        identifier: identifier.unwrap(),
+        is_extern,
+        is_public,
+        type_declaration: TypeDeclaration::new(
+            generic_parameters.unwrap_or(vec![]),
+            extends.unwrap_or(vec![]),
+            declarations
+        ),
+        impl_ctor
+    }
 }
 
 fn build_module(is_extern: bool, is_public: bool, pair: Pair<Rule>) -> Declaration {
@@ -240,7 +357,7 @@ fn build_declaration(declaration_pair: Pair<Rule>) -> Declaration {
             Rule::r#pub => {
                 is_public = true;
             }
-            Rule::interface => { 
+            Rule::interface => {
                 declaration = Some(build_interface(is_extern, is_public, pair));
             },
             Rule::implementation => {
@@ -252,6 +369,12 @@ fn build_declaration(declaration_pair: Pair<Rule>) -> Declaration {
             Rule::function => {
                 declaration = Some(build_function(is_extern, is_public, pair));
             },
+            Rule::prop => {
+                declaration = Some(build_prop(pair));
+            }
+            Rule::field => {
+                declaration = Some(build_field(pair));
+            }
             _ => panic!("Expected only interface, implementation, module, or function rules; found {}", pair)
         }
     }
@@ -265,8 +388,8 @@ fn build_identifier(pair: Pair<Rule>) -> Identifier {
                 name: String::from(pair.as_str())
             }
         }
-        _ => panic!("Expected an identifier.") 
-    } 
+        _ => panic!("Expected an identifier.")
+    }
 }
 
 fn build_fqn(fqn_pair: Pair<Rule>) -> Fqn {
@@ -291,7 +414,7 @@ fn build_compilation_unit(pair: Pair<Rule>)-> CompilationUnit {
     for pair in pair.into_inner() {
         match pair.as_rule() {
             Rule::namespace => {
-                let fqn_pair = pair.into_inner().next().unwrap(); 
+                let fqn_pair = pair.into_inner().next().unwrap();
                 namespace = Some(build_fqn(fqn_pair));
             }
             Rule::declaration => {
@@ -299,7 +422,7 @@ fn build_compilation_unit(pair: Pair<Rule>)-> CompilationUnit {
             }
             Rule::EOI => {} // ignore
             _ => panic!("Expected only namespace, declaration, or EOI rules, found: {}", pair)
-        }    
+        }
     }
 
     CompilationUnit {
diff --git a/src/parser/deimos.pest b/src/parser/deimos.pest
index f2061ac..342a139 100644
--- a/src/parser/deimos.pest
+++ b/src/parser/deimos.pest
@@ -6,22 +6,22 @@ identifier = @{ identifier_start_char ~ identifier_char* }
 identifier_start_char = { 'a'..'z' | 'A'..'Z' | "_" }
 identifier_char = { 'a'..'z' | 'A'..'Z' | '0'..'9' | "_" }
 
-declaration = { extern? ~ pub? ~ ( interface | implementation | module | function ) }
+declaration = { extern? ~ pub? ~ ( interface | implementation | module | function | prop | field ) }
 extern = { "extern" }
 pub = { "pub" }
 
 interface = { "int" ~ identifier ~ generic_parameters_declaration? ~ extends_list? ~ ( "{" ~ declaration* ~ "}" )? }
 extends_list = { ":" ~ type ~ ( "+" ~ type )* }
 
-implementation = { "impl" ~ identifier ~ generic_parameters_declaration? ~ impl_ctor? ~ extends_list? }
+implementation = { "impl" ~ identifier ~ generic_parameters_declaration? ~ impl_ctor? ~ extends_list? ~ ( "{" ~ declaration* ~ "}" )? }
 impl_ctor = { "(" ~ impl_ctor_args? ~ ")" }
 impl_ctor_args = { impl_ctor_arg ~ ( "," ~ impl_ctor_arg )* }
-impl_ctor_arg = { fld? ~ identifier ~ ":" ~ type }
+impl_ctor_arg = { fld? ~ identifier ~ ( ":" ~ type )? }
 fld = { "fld" }
 
 module = { "mod" ~ identifier ~ "{" ~ declaration* ~ "}" }
 
-property = { identifier ~ ":" ~ type }
+property = { identifier ~ ( ":" ~ type )? }
 
 function = { "fn" ~ generic_parameters_declaration? ~ identifier ~ "(" ~ args_list? ~ ")" ~ ( ":" ~ type )? ~ ( function_body | function_equals_body ) }
 function_equals_body = { "=" ~ expression }
@@ -37,6 +37,9 @@ generic_argument = { fqn }
 args_list = { arg ~ ( "," ~ arg )* }
 arg = { identifier ~ ( ":" ~ "..."? ~ type )? }
 
+prop = { identifier ~ ":" ~ type }
+field = { fld ~ identifier ~ ":" ~ type }
+
 statement = { call_stmt }
 
 call_stmt = { call_expr }