From 76541040c9c2f25674de31819f48ddb12b5ee1d2 Mon Sep 17 00:00:00 2001
From: Klesti Selimaj <klesti.selimay@icloud.com>
Date: Sun, 28 Jun 2026 05:45:13 +0200
Subject: [PATCH] Function types

---
 crates/codegen/src/fmt/mod.rs            | 29 ++++++++++++++++++++++
 crates/codegen/src/lib.rs                | 31 +++++++++++++++++++++++-
 crates/parser/src/ast/mod.rs             | 14 +++++++++++
 crates/parser/src/grammar.pest           | 24 +++++++++++++++++-
 crates/parser/src/parser/common/types.rs |  6 +++++
 mist-test/src/main.mist                  |  2 ++
 6 files changed, 104 insertions(+), 2 deletions(-)

diff --git a/crates/codegen/src/fmt/mod.rs b/crates/codegen/src/fmt/mod.rs
index f549491..0dd8128 100644
--- a/crates/codegen/src/fmt/mod.rs
+++ b/crates/codegen/src/fmt/mod.rs
@@ -200,10 +200,39 @@ impl GetMist for TypeExpr {
             Self::Dyn(ty) => {
                 format!("dyn {}", ty.get_mist())
             }
+            Self::Fn {
+                kind,
+                return_type,
+                params,
+            } => {
+                format!(
+                    "{} {}({})",
+                    return_type.get_mist(),
+                    kind.get_mist(),
+                    params
+                        .iter()
+                        .map(TypeExpr::get_mist)
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                )
+            }
         }
     }
 }
 
+impl GetMist for FnKind {
+    fn get_mist(&self) -> String {
+        match self {
+            Self::Fn => "fn",
+            Self::UnsafeFn => "unsafe fn",
+            Self::FnClosure => "Fn",
+            Self::FnMut => "FnMut",
+            Self::FnOnce => "FnOnce",
+        }
+        .to_string()
+    }
+}
+
 impl GetMist for ExprPath {
     fn get_mist(&self) -> String {
         self.0
diff --git a/crates/codegen/src/lib.rs b/crates/codegen/src/lib.rs
index 9919ac3..cd11bf1 100644
--- a/crates/codegen/src/lib.rs
+++ b/crates/codegen/src/lib.rs
@@ -239,7 +239,6 @@ impl GetRust for TypeExpr {
             Self::UnsafePtr { mutable, ty } => {
                 let mutable = if *mutable { "mut " } else { "const " };
                 format!("*{mutable}{}", ty.get_rust())
-                
             }
 
             Self::Ref {
@@ -262,10 +261,40 @@ impl GetRust for TypeExpr {
             Self::Dyn(ty) => {
                 format!("dyn {}", ty.get_rust())
             }
+
+            Self::Fn {
+                kind,
+                return_type,
+                params,
+            } => {
+                format!(
+                    "{} -> {}({})",
+                    kind.get_rust(),
+                    return_type.get_rust(),
+                    params
+                        .iter()
+                        .map(TypeExpr::get_rust)
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                )
+            }
         }
     }
 }
 
+impl GetRust for FnKind {
+    fn get_rust(&self) -> String {
+        match self {
+            Self::Fn => "fn",
+            Self::UnsafeFn => "unsafe fn",
+            Self::FnClosure => "Fn",
+            Self::FnMut => "FnMut",
+            Self::FnOnce => "FnOnce",
+        }
+        .to_string()
+    }
+}
+
 impl GenRust for Pattern {
     fn gen_rust(&self, ctx: &mut Context, cg: &mut RustCodegen) {
         match self {
diff --git a/crates/parser/src/ast/mod.rs b/crates/parser/src/ast/mod.rs
index 5c61cb3..429c9c0 100644
--- a/crates/parser/src/ast/mod.rs
+++ b/crates/parser/src/ast/mod.rs
@@ -17,6 +17,15 @@ pub struct Identifier(pub String);
 #[derive(Debug, Clone, Serialize, Default)]
 pub struct ParamList(pub Vec<VarDecl>);
 
+#[derive(Debug, Clone, Serialize, PartialEq, Eq, Hash)]
+pub enum FnKind {
+    Fn,
+    UnsafeFn,
+    FnClosure,
+    FnOnce,
+    FnMut,
+}
+
 #[derive(Debug, Clone, Serialize, PartialEq, Eq, Hash)]
 pub enum TypeExpr {
     Ref {
@@ -33,6 +42,11 @@ pub enum TypeExpr {
     StaticFn(Vec<TypeExpr>, Option<Box<TypeExpr>>),
     Tuple(Vec<TypeExpr>),
     Lifetime(Identifier),
+    Fn {
+        kind: FnKind,
+        return_type: Box<TypeExpr>,
+        params: Vec<TypeExpr>,
+    },
 }
 
 #[derive(Debug, Clone, Serialize)]
diff --git a/crates/parser/src/grammar.pest b/crates/parser/src/grammar.pest
index ad70449..4cfbbe1 100644
--- a/crates/parser/src/grammar.pest
+++ b/crates/parser/src/grammar.pest
@@ -111,12 +111,34 @@ ref_type = {
     mutable? ~ lifetime? ~ "&"
 }
 
+fn_kind_fn      = { "fn" }
+fn_kind_unsafe  = { "unsafe" ~ "fn" }
+fn_kind_closure = { "Fn" }
+fn_kind_once    = { "FnOnce" }
+fn_kind_mut     = { "FnMut" }
+
+fn_kind = _{
+    fn_kind_fn
+  | fn_kind_unsafe
+  | fn_kind_closure
+  | fn_kind_once
+  | fn_kind_mut
+}
+
+fn_type = {
+    fn_kind ~ "(" ~ (type_expr ~ ("," ~ type_expr)*)? ~ ")"
+}
+
 dyn_type = {
     "dyn" ~ type_expr
 }
 
+void_type = {
+    "void"
+}
+
 type_expr = {
-    (path_type | tuple_type | dyn_type) ~ (unsafe_ref_type | ref_type)*
+    (void_type | path_type | tuple_type | dyn_type) ~ (unsafe_ref_type | ref_type | fn_type)*
 }
 
 lifetime = {
diff --git a/crates/parser/src/parser/common/types.rs b/crates/parser/src/parser/common/types.rs
index fbca7ea..64b032d 100644
--- a/crates/parser/src/parser/common/types.rs
+++ b/crates/parser/src/parser/common/types.rs
@@ -42,6 +42,10 @@ impl<'a> TryFrom<pest::iterators::Pair<'a, Rule>> for TypeExpr {
                             };
                         }
 
+                        Rule::fn_type => {
+                            
+                        }
+
                         _ => AstError::bug_unimplemented(ref_pair)?,
                     }
                 }
@@ -50,7 +54,9 @@ impl<'a> TryFrom<pest::iterators::Pair<'a, Rule>> for TypeExpr {
             }
             Rule::lifetime => Ok(TypeExpr::Lifetime(inner.next().unwrap().try_into()?)),
 
+            Rule::void_type => Ok(TypeExpr::Tuple(Vec::new())),
             Rule::tuple_type => Ok(TypeExpr::Tuple(collect_recovered(inner)?)),
+
             Rule::path_type => Ok(TypeExpr::Path(
                 Path::try_from(inner.next().unwrap())?,
                 inner.next().map(Generics::try_from).transpose()?,
diff --git a/mist-test/src/main.mist b/mist-test/src/main.mist
index e5fd2e4..689fc94 100644
--- a/mist-test/src/main.mist
+++ b/mist-test/src/main.mist
@@ -15,4 +15,6 @@ void main()
     items::impl_test::run_tests();
     items::attribute_test::run_tests();
     println!("\x1b[32m\nAll tests passed!\x1b[0m");
+
+    void fn() hello = () => {};
 }