Parse minimal function declaration

src/codegen/mod.rs

@@ -3,6 +3,7 @@ use crate::syntax::ast::ModuleAST;
 mod binding;
 mod expression;
 mod module_ast;
+mod top_level_construct;
 
 /// Trait that the AST and its nodes implement to support transformation to PHP
 trait Transpilable {

src/codegen/module_ast.rs

@@ -18,7 +18,7 @@ impl Transpilable for ModuleAST {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::syntax::ast::{Binding, Expression, ValBinding};
+    use crate::syntax::ast::{Binding, Expression, TopLevelConstruct, ValBinding};
 
     #[test]
     fn module_ast_should_transpile() {
@@ -31,7 +31,7 @@ mod tests {
         });
 
         let module = ModuleAST {
-            bindings: vec![binding],
+            bindings: vec![TopLevelConstruct::Binding(binding)],
         };
 
         let result = module.transpile();

src/codegen/top_level_construct.rs

@@ -0,0 +1,12 @@
+use crate::syntax::ast::TopLevelConstruct;
+
+use super::Transpilable;
+
+impl Transpilable for TopLevelConstruct {
+    fn transpile(&self) -> String {
+        match self {
+            TopLevelConstruct::Binding(binding) => binding.transpile(),
+            TopLevelConstruct::FunctionDeclaration(_) => todo!(),
+        }
+    }
+}

src/lexic/scanner/identifier.rs

@@ -6,6 +6,7 @@ fn str_is_keyword(s: &String) -> Option<TokenType> {
     match s.as_str() {
         "var" => Some(TokenType::VAR),
         "val" => Some(TokenType::VAL),
+        "fun" => Some(TokenType::FUN),
         _ => None,
     }
 }

src/lexic/token.rs

@@ -16,6 +16,7 @@ pub enum TokenType {
     VAR,
     VAL,
     EOF,
+    FUN,
 }
 
 #[derive(Debug)]

src/main.rs

@@ -51,9 +51,7 @@ fn main() {
     let cli = Cli::parse();
 
     match &cli.command {
-        Some(Commands::C {
-            file: input,
-        }) => file::compile_file(input),
+        Some(Commands::C { file: input }) => file::compile_file(input),
         Some(Commands::R {}) => {
             println!("{}", get_copyright());
             let _ = repl::run();

src/syntax/ast.rs

@@ -1,24 +1,39 @@
 pub struct ModuleAST {
-    pub bindings: Vec<Binding>,
+    pub bindings: Vec<TopLevelConstruct>,
 }
 
+#[derive(Debug)]
+pub enum TopLevelConstruct {
+    Binding(Binding),
+    FunctionDeclaration(FunctionDeclaration),
+}
+
+#[derive(Debug)]
+pub struct FunctionDeclaration {
+    pub identifier: Box<String>,
+}
+
+#[derive(Debug)]
 pub enum Binding {
     Val(ValBinding),
     Var(VarBinding),
 }
 
+#[derive(Debug)]
 pub struct ValBinding {
     pub datatype: Option<String>,
     pub identifier: Box<String>,
     pub expression: Expression,
 }
 
+#[derive(Debug)]
 pub struct VarBinding {
     pub datatype: Option<String>,
     pub identifier: Box<String>,
     pub expression: Expression,
 }
 
+#[derive(Debug)]
 pub enum Expression {
     Number(Box<String>),
     String(Box<String>),

src/syntax/binding.rs

@@ -120,7 +120,9 @@ pub fn try_parse<'a>(tokens: &'a Vec<Token>, pos: usize) -> Option<SyntaxResult>
         })
     };
 
-    Some(SyntaxResult::Ok(binding))
+    Some(SyntaxResult::Ok(super::ast::TopLevelConstruct::Binding(
+        binding,
+    )))
 }
 
 /// Expects the token at `pos` to be of type `token_type`
@@ -149,7 +151,7 @@ fn try_operator(tokens: &Vec<Token>, pos: usize, operator: String) -> Result3<&T
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::lexic::get_tokens;
+    use crate::{lexic::get_tokens, syntax::ast::TopLevelConstruct};
 
     #[test]
     fn should_parse_val_binding() {
@@ -157,7 +159,7 @@ mod tests {
         let binding = try_parse(&tokens, 0).unwrap();
 
         match binding {
-            SyntaxResult::Ok(Binding::Val(binding)) => {
+            SyntaxResult::Ok(TopLevelConstruct::Binding(Binding::Val(binding))) => {
                 assert_eq!("identifier", format!("{}", binding.identifier));
             }
             _ => panic!(),
@@ -195,7 +197,7 @@ mod tests {
         let binding = try_parse(&tokens, 0).unwrap();
 
         match binding {
-            SyntaxResult::Ok(Binding::Val(binding)) => {
+            SyntaxResult::Ok(TopLevelConstruct::Binding(Binding::Val(binding))) => {
                 assert_eq!(Some(String::from("Num")), binding.datatype);
                 assert_eq!("identifier", format!("{}", binding.identifier));
             }
@@ -206,11 +208,11 @@ mod tests {
         let binding = try_parse(&tokens, 0).unwrap();
 
         match binding {
-            SyntaxResult::Ok(Binding::Var(binding)) => {
+            SyntaxResult::Ok(TopLevelConstruct::Binding(Binding::Var(binding))) => {
                 assert_eq!(Some(String::from("Bool")), binding.datatype);
                 assert_eq!("identifier", format!("{}", binding.identifier));
             }
-            _ => panic!(),
+            _ => panic!("D: {:?}", binding),
         }
     }
 

src/syntax/function_declaration.rs

@@ -0,0 +1,356 @@
+use crate::{
+    error_handling::SyntaxError,
+    lexic::token::{Token, TokenType},
+    utils::Result3,
+};
+
+use super::{
+    ast::{FunctionDeclaration, TopLevelConstruct},
+    utils::try_token_type,
+    SyntaxResult,
+};
+
+pub fn try_parse<'a>(tokens: &'a Vec<Token>, pos: usize) -> Option<SyntaxResult> {
+    let mut current_pos = pos;
+
+    // `fun` keyword
+    let fun_keyword = match try_token_type(tokens, current_pos, TokenType::FUN) {
+        Result3::Ok(t) => t,
+        Result3::Err(_token) => return None,
+        Result3::None => return None,
+    };
+    current_pos += 1;
+
+    // Parse identifier
+    let identifier = match try_token_type(tokens, current_pos, TokenType::Identifier) {
+        Result3::Ok(t) => t,
+        Result3::Err(t) => {
+            // The parser found a token, but it's not an identifier
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be an identifier after a `fun` token, but found `{}`",
+                    t.value
+                ),
+                error_start: t.position,
+                error_end: t.get_end_position(),
+            }));
+        }
+        Result3::None => {
+            // The parser didn't find any token
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be an identifier after a `fun` token, but found nothing"
+                ),
+                error_start: fun_keyword.position,
+                error_end: fun_keyword.get_end_position(),
+            }));
+        }
+    };
+    current_pos += 1;
+
+    // Parse an opening paren
+    let opening_paren = match try_token_type(tokens, current_pos, TokenType::LeftParen) {
+        Result3::Ok(t) => t,
+        Result3::Err(t) => {
+            // The parser found a token, but it's not an opening paren
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be an opening paren after the identifier, but found `{}`",
+                    t.value
+                ),
+                error_start: t.position,
+                error_end: t.get_end_position(),
+            }));
+        }
+        Result3::None => {
+            // The parser didn't find any token
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be an opening paren after the identifier, but found nothing"
+                ),
+                error_start: identifier.position,
+                error_end: identifier.get_end_position(),
+            }));
+        }
+    };
+    current_pos += 1;
+
+    // Parse a closing paren
+    let closing_paren = match try_token_type(tokens, current_pos, TokenType::RightParen) {
+        Result3::Ok(t) => t,
+        Result3::Err(t) => {
+            // The parser found a token, but it's not an opening paren
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be a closing paren after the parameter list, but found `{}`",
+                    t.value
+                ),
+                error_start: t.position,
+                error_end: t.get_end_position(),
+            }));
+        }
+        Result3::None => {
+            // The parser didn't find any token
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be a closing paren after the parameter list, but found nothing"
+                ),
+                error_start: opening_paren.position,
+                error_end: opening_paren.get_end_position(),
+            }));
+        }
+    };
+    current_pos += 1;
+
+    // Parse opening brace
+    let opening_brace = match try_token_type(tokens, current_pos, TokenType::LeftBrace) {
+        Result3::Ok(t) => t,
+        Result3::Err(t) => {
+            // The parser found a token, but it's not an opening brace
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be an opening brace after the parameter list, but found `{}`",
+                    t.value
+                ),
+                error_start: t.position,
+                error_end: t.get_end_position(),
+            }));
+        }
+        Result3::None => {
+            // The parser didn't find any token
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be an opening brace after the parameter list, but found nothing"
+                ),
+                error_start: closing_paren.position,
+                error_end: closing_paren.get_end_position(),
+            }));
+        }
+    };
+    current_pos += 1;
+
+    // Parse closing brace
+    let closing_brace = match try_token_type(tokens, current_pos, TokenType::RightBrace) {
+        Result3::Ok(t) => t,
+        Result3::Err(t) => {
+            // The parser found a token, but it's not an opening brace
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be a closing brace after the function body, but found `{}`",
+                    t.value
+                ),
+                error_start: t.position,
+                error_end: t.get_end_position(),
+            }));
+        }
+        Result3::None => {
+            // The parser didn't find any token
+            return Some(SyntaxResult::Err(SyntaxError {
+                reason: format!(
+                    "There should be a closing brace after the function body, but found nothing"
+                ),
+                error_start: opening_brace.position,
+                error_end: opening_brace.get_end_position(),
+            }));
+        }
+    };
+
+    // Construct and return the function declaration
+    Some(SyntaxResult::Ok(TopLevelConstruct::FunctionDeclaration(
+        FunctionDeclaration {
+            identifier: Box::new(identifier.value.clone()),
+        },
+    )))
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{lexic::get_tokens, syntax::ast::TopLevelConstruct};
+
+    use super::*;
+
+    #[test]
+    fn should_return_none_on_wrong_initial_token() {
+        let tokens = get_tokens(&String::from("val identifier = 20")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+
+        assert!(fun_decl.is_none());
+    }
+
+    #[test]
+    fn should_not_parse_fun_without_identifier() {
+        let tokens = get_tokens(&String::from("fun = 20")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be an identifier after a `fun` token, but found `=`"
+                );
+                assert_eq!(err.error_start, 4);
+                assert_eq!(err.error_end, 5);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+
+        let tokens = get_tokens(&String::from("fun")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be an identifier after a `fun` token, but found nothing"
+                );
+                assert_eq!(err.error_start, 0);
+                assert_eq!(err.error_end, 3);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+    }
+
+    #[test]
+    fn should_not_parse_fun_without_parens() {
+        let tokens = get_tokens(&String::from("fun id =")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be an opening paren after the identifier, but found `=`"
+                );
+                assert_eq!(err.error_start, 7);
+                assert_eq!(err.error_end, 8);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+
+        let tokens = get_tokens(&String::from("fun id")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be an opening paren after the identifier, but found nothing"
+                );
+                assert_eq!(err.error_start, 4);
+                assert_eq!(err.error_end, 6);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+    }
+
+    #[test]
+    fn should_not_parse_fun_without_closing_paren() {
+        let tokens = get_tokens(&String::from("fun id(=")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be a closing paren after the parameter list, but found `=`"
+                );
+                assert_eq!(err.error_start, 7);
+                assert_eq!(err.error_end, 8);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+
+        let tokens = get_tokens(&String::from("fun id(")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be a closing paren after the parameter list, but found nothing"
+                );
+                assert_eq!(err.error_start, 6);
+                assert_eq!(err.error_end, 7);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+    }
+
+    #[test]
+    fn should_not_parse_fun_without_opening_brace() {
+        let tokens = get_tokens(&String::from("fun id() =")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be an opening brace after the parameter list, but found `=`"
+                );
+                assert_eq!(err.error_start, 9);
+                assert_eq!(err.error_end, 10);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+
+        let tokens = get_tokens(&String::from("fun id()")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be an opening brace after the parameter list, but found nothing"
+                );
+                assert_eq!(err.error_start, 7);
+                assert_eq!(err.error_end, 8);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+    }
+
+    #[test]
+    fn should_not_parse_fun_without_closing_brace() {
+        let tokens = get_tokens(&String::from("fun id() { 20")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be a closing brace after the function body, but found `20`"
+                );
+                assert_eq!(err.error_start, 11);
+                assert_eq!(err.error_end, 13);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+
+        let tokens = get_tokens(&String::from("fun id() {")).unwrap();
+        let fun_decl = try_parse(&tokens, 0);
+
+        match fun_decl {
+            Some(SyntaxResult::Err(err)) => {
+                assert_eq!(
+                    err.reason,
+                    "There should be a closing brace after the function body, but found nothing"
+                );
+                assert_eq!(err.error_start, 9);
+                assert_eq!(err.error_end, 10);
+            }
+            _ => panic!("Expected an error: {:?}", fun_decl),
+        }
+    }
+
+    #[test]
+    fn should_parse_simple_function_declaration() {
+        let tokens = get_tokens(&String::from("fun id() {}")).unwrap();
+        let function_declaration = try_parse(&tokens, 0).unwrap();
+
+        match function_declaration {
+            SyntaxResult::Ok(TopLevelConstruct::FunctionDeclaration(declaration)) => {
+                assert_eq!(declaration.identifier, Box::new(String::from("id")));
+            }
+            _ => panic!(
+                "Expected a function declaration: {:?}",
+                function_declaration
+            ),
+        }
+    }
+}

src/syntax/mod.rs

@@ -2,16 +2,21 @@ use crate::error_handling::{MistiError, SyntaxError};
 
 mod binding;
 mod expression;
+mod function_declaration;
+mod utils;
+
 pub mod ast;
 
-use ast::{Binding, ModuleAST};
 use crate::lexic::token::Token;
+use ast::{Binding, ModuleAST};
 
+use self::ast::TopLevelConstruct;
 
+#[derive(Debug)]
 pub enum SyntaxResult {
     ///
     /// A construct has been found
-    Ok(Binding),
+    Ok(TopLevelConstruct),
     ///
     /// No construct was found
     None,

src/syntax/utils.rs

@@ -0,0 +1,15 @@
+use crate::{
+    lexic::token::{Token, TokenType},
+    utils::Result3,
+};
+
+pub fn try_token_type(tokens: &Vec<Token>, pos: usize, token_type: TokenType) -> Result3<&Token> {
+    match tokens.get(pos) {
+        Some(t) if t.token_type == token_type => Result3::Ok(t),
+        Some(t) if t.token_type == TokenType::Semicolon || t.token_type == TokenType::EOF => {
+            Result3::None
+        }
+        Some(t) => Result3::Err(t),
+        None => Result3::None,
+    }
+}