Merge pull request #17 from mist-go/update

Update
This commit is contained in:
2026-07-12 14:08:39 +02:00
committed by GitHub
13 changed files with 295 additions and 136 deletions
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@@ -0,0 +1,88 @@
---
title: Mist 0.4.0 is released, virtual methods, array types, and more
author: Klesti Selimaj
date: 2026-07-12
---
## New Features
### Virtual Methods
The `virtual` keyword enables polymorphic dispatch through vtables. Methods marked `virtual` can be overridden in subclasses and will be dispatched dynamically at runtime:
```mist
pub class Animal
{
pub virtual void speak(&self)
{
println!("...");
}
}
class Dog : Animal
{
void speak(&self) override
{
println!("Woof!");
}
}
```
### Array Types
Fixed-size array types are now supported with `[T; N]` syntax:
```mist
[i32; 10] numbers; // Array of 10 i32s
[str&; 3] names; // Array of 3 string references
```
### Tuple Variable Declarations
Tuple variables can now be declared with explicit type annotations using `as`:
```mist
(i32, bool) as x, y = (1, true);
i32 a, b = (1, 2, 3);
```
### Include Directives
C-style include directives for importing external files and crates:
```mist
#include <stdio.h> // Global include
pub use my_crate::module; // Use include
#include "local.mist" // Local include
```
## Syntax Changes
### Allman Style Struct/Enum Fields
Struct and enum fields now use semicolons instead of commas:
```mist
// Before (v0.3.x)
struct Point { i32 x, i32 y }
// After (v0.4.0)
struct Point { i32 x; i32 y; }
```
## Bug Fixes
- Fixed default initializers in classes
- Fixed the mapping system for error remapping
- Fixed include manifest path resolution
- Fixed various analyzer bugs
- Fixed the publish command
- Fixed completion pollution in LSP
## Improvements
- Updated bootstrap infrastructure
- Migrated to core library for `c_void` and classes
- Removed unnecessary lifetime annotations
- Fixed generics and function type handling
+2 -2
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@@ -15,8 +15,8 @@ Outer attributes apply to the next item:
```mist
#[derive(Debug, Clone)]
struct Point {
i32 x,
i32 y,
i32 x;
i32 y;
}
#[test]
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@@ -33,6 +33,29 @@ class Player
}
```
### Virtual Methods
The `virtual` keyword marks methods as dispatchable through the vtable, enabling polymorphic behavior:
```mist
pub class Animal
{
str& name;
pub constructor(str& name)
{
self.name = name;
}
pub virtual void speak(&self)
{
println!("...");
}
}
```
When a method is marked `virtual`, it can be overridden in subclasses and will be dispatched dynamically at runtime through the vtable. Non-virtual methods are called statically.
### Inheritance
```mist
@@ -59,6 +82,8 @@ void speak(&self) override(Animal)
}
```
Methods marked `override` are automatically virtual if the parent method is virtual. The semantic analyzer validates that overridden methods match the parent's signature.
### Implementations
You can implement directly on the class body:
@@ -78,113 +103,6 @@ class Circle
}
```
### Under the Hood
---
A class `Dog : Animal` generates:
1. A Rust struct with a `_super: Animal` field (or `_vptr: &'static [*const c_void]` for root classes)
2. A vtable constant with function pointers for each public method
3. An `impl` block with `Deref<Target = Animal>` and `DerefMut`
4. Method trampolines (`__m_<name>`) that are dispatched through the vtable
5. A `new()` constructor that initializes via `MaybeUninit` and calls the user's `constructor(&mut self)`
The vtable is unified: parent entries are copied, overridden entries replace parent slots, and new methods are appended.
### Safety
Classes use `MaybeUninit::zeroed().assume_init()` inside the generated `new()` function — an inherently unsafe operation. This raises a natural question: **Are class constructors unsafe?**
The answer is **no**. The compiler statically verifies that every field is initialized before the constructor returns, eliminating the undefined behavior that raw `MaybeUninit` would normally carry.
#### Static Field Initialization Verification
When a class has a constructor, the semantic checker (`check_class_semantics`) collects every declared field and walks the constructor body to prove each one is written to:
1. **Direct assignment tracking** — Expressions like `self.field = value` are recognized as mutations of `field`. The analyzer checks for `=` and `->` operators whose left-hand side is a `self.field` path.
2. **`&mut self.field` tracking** — Taking a mutable reference to a field (`&mut self.field`) also counts as initializing it, since the reference can only be taken if the field is being set up.
3. **Transitive method calls** — If the constructor calls `self.helper()`, the analyzer follows into `helper`'s body and tracks which fields *it* initializes. This transitively propagates through nested calls:
```mist
class Player
{
str& name;
i32 health;
pub constructor(str& name)
{
self.name = name;
self.setup_health();
}
void setup_health(&mut self)
{
self.health = 100; // Counts toward constructor's verification
}
}
```
4. **Branch intersection** — For `if`/`else`, `match`, and loops, fields must be initialized in **all** branches. If one branch initializes `x` but another does not, `x` is considered uninitialized. This ensures soundness regardless of the runtime path:
```mist
pub constructor(bool flag)
{
if flag {
self.health = 100;
} else {
self.health = 0;
}
// Both branches init health ✓
}
```
5. **Super initialization** — When a class inherits, the `_super` field is added to the required-field list. Any assignment to `super` counts:
```mist
pub constructor(str& name)
{
super = Super::new(name);
}
```
If any field is uninitialized after the full analysis, a compile-time error is reported with the field's exact source location:
```
class field `Player.health` is uninitialized
```
#### Override Validation at Compile Time
When a method uses the `override` keyword, the codegen emits a hidden test function that verifies the Deref chain at compile time:
```rust
#[allow(invalid_value)]
fn __test_vt() {
let this: &Self = &unsafe { std::mem::MaybeUninit::<Self>::zeroed().assume_init() };
let _: &Target = this; // Forces compiler to check Deref<Target = Target>
}
```
This ensures `&Self` can always deref into the base class type. If the inheritance hierarchy is invalid, the Rust compiler rejects it.
#### VTable Safety
The `_vptr` (vtable pointer) is set *twice* during construction:
1. **Before** the constructor body runs — enabling virtual dispatch inside the constructor itself
2. **After** the constructor body — in case a base-class constructor ran and overwrote the pointer
This ensures that virtual method calls work correctly even during object construction, without exposing uninitialized memory through the vtable.
#### Summary
| Risk | Mitigation |
|------|-----------|
| Uninitialized fields via `MaybeUninit` | Static field-initialization verification rejects incomplete constructors |
| UB from reading uninitialized fields | Intersection analysis ensures all branches init the same fields |
| Invalid override signatures | Compile-time Deref test validates the inheritance chain |
| Vtable corruption during construction | `_vptr` is set before and after the constructor body |
| Unsafe code in generated constructors | `#[allow(invalid_value)]` is scoped to the generated `new()` only |
The `MaybeUninit` pattern is an implementation detail of the generated code — the Mist compiler proves soundness at the language level, so the user's constructor body is safe Mist code with no manual `unsafe` annotations required.
For details on how classes are compiled — vtable layout, constructor codegen, and safety verification — see [Class Internals](/docs/internals/classes).
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@@ -1,6 +1,6 @@
---
title: Modules & Imports
description: Module declarations, imports, re-exports, and module resolution rules.
description: Module declarations, imports, re-exports, include directives, and module resolution rules.
icon: FolderTree
---
@@ -18,6 +18,26 @@ use std::collections::HashMap;
pub use my_module::MyType;
```
### Include Directives
Mist supports C-style include directives for
```mist
// Global include (std::Display)
// Includes all of the items *inside* the path
#include <std/fmt>
// Use include (std::Display)
// Includes *the path* itelf to the root.
#use std::fmt::Display;
// Local include
// Textual include, transpiles to rust include! macro via .rs extension
#include "my_local_module.mist"
```
Include directives allow you to bring in external code without using the module system, which is useful for C interop and local file organization.
### Module Resolution
Mist maps the module tree to Rust's module system:
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@@ -9,13 +9,13 @@ icon: Box
```mist
pub struct Point
{
i32 x,
i32 y,
i32 x;
i32 y;
}
pub struct Generic<T>
{
T value,
T value;
}
```
@@ -24,8 +24,8 @@ Fields can be public or private:
```mist
struct User
{
pub str& name,
i32 age, // private
pub str& name;
i32 age; // private
}
```
@@ -34,19 +34,19 @@ struct User
```mist
pub enum Option<T>
{
Some(T),
None,
Some(T);
None;
}
pub enum Message
{
Quit,
Move(i32, i32),
Write { str& content, i32 length },
Quit;
Move(i32, i32);
Write { str& content; i32 length; };
}
```
Enum variants can be:
- **Named** — `Variant`
- **Tuple** — `Variant(T1, T2)`
- **Struct** — `Variant { T1 field1, T2 field2 }`
- **Struct** — `Variant { T1 field1; T2 field2; }`
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@@ -19,13 +19,14 @@ true // Boolean
false // Boolean
"hello" // String
(1, true, "x") // Tuple
[1, 2, 3] // Array
```
### Identifiers & Keywords
Keywords are reserved and cannot be used as identifiers:
`if`, `else`, `fn`, `for`, `while`, `match`, `return`, `break`, `continue`, `struct`, `enum`, `class`, `trait`, `impl`, `use`, `pub`, `mut`, `let`, `true`, `false`, `dyn`, `loop`, `unsafe`, `override`, `const`, `type`
`if`, `else`, `fn`, `for`, `while`, `match`, `return`, `break`, `continue`, `struct`, `enum`, `class`, `trait`, `impl`, `use`, `pub`, `mut`, `let`, `true`, `false`, `dyn`, `loop`, `unsafe`, `override`, `const`, `type`, `virtual`
Identifiers follow the pattern `[a-zA-Z_][a-zA-Z0-9_]*`.
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@@ -14,6 +14,8 @@ i32 'a& // Reference with lifetime
i32 unsafe& // Const pointer
i32 mut unsafe& // Mutable pointer
(i32, bool) // Tuple type
i32[]& // Array type (static non-fixed size)
i32[10] // Array type (fixed size)
bool fn(i32) // Function pointer type
bool Fn(i32) // Closure trait (Fn)
bool FnMut(i32) // Closure trait (FnMut)
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@@ -5,14 +5,15 @@ icon: Variable
---
```mist
let x = 42; // Type-inferred immutable
let mut y = 10; // Mutable variable
i32 z = 100; // Explicit type annotation
str& s = "hello"; // Typed string reference
bool b = true; // Typed boolean
f64 f = 3.14; // Typed float
let (a, b) = (1, "two"); // Destructuring
let (x, (y, z)) = (1, (2, 3)); // Nested destructuring
let x = 42; // Type-inferred immutable
let mut y = 10; // Mutable variable
i32 z = 100; // Explicit type annotation
str& s = "hello"; // Typed string reference
bool b = true; // Typed boolean
f64 f = 3.14; // Typed float
(i32, str&) as x, y = (1, "hello"); // Typed tuple destructuring
let (a, b) = (1, "two"); // Destructuring
let (x, (y, z)) = (1, (2, 3)); // Nested destructuring
```
Variable declarations follow either of two forms:
@@ -22,6 +23,16 @@ let <pattern> [= <expr>];
<type> <pattern> [= <expr>];
```
### Tuple Variable Declarations
Tuple variables can be declared with explicit type annotations using `as`:
```mist
(i32, bool) as x, y = (1, true);
i32 a, b = (1, 2, 3);
```
### Const and Static
```mist
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@@ -13,7 +13,7 @@ Mist is currently distributed as a Cargo crate. To get started, you'll need to h
Run the following command to install the Mist toolchain:
```bash title="Terminal"
cargo install mist-lang@0.3.8-alpha.0
cargo install mist-lang@0.4.0
```
> (ℹ) For a more streamlined development experience, Install the following VSCode extensions:
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@@ -0,0 +1,118 @@
---
title: Class Internals
description: How classes are compiled under the hood — vtable layout, code generation, and safety verification.
icon: Shield
---
This page covers the implementation details of Mist classes. You don't need to read this to use classes — it's here for curiosity and compiler contributors.
### Under the Hood
A class `Dog : Animal` generates:
1. A Rust struct with a `_super: Animal` field (or `_vptr: &'static [*const c_void]` for root classes)
2. A vtable constant with function pointers for each public method
3. An `impl` block with `Deref<Target = Animal>` and `DerefMut`
4. Method trampolines (`__m_<name>`) that are dispatched through the vtable
5. A `new()` constructor that initializes via `MaybeUninit` and calls the user's `constructor(&mut self)`
The vtable is unified: parent entries are copied, overridden entries replace parent slots, and new methods are appended.
### Safety
Classes use `MaybeUninit::zeroed().assume_init()` inside the generated `new()` function — an inherently unsafe operation. This raises a natural question: **Are class constructors unsafe?**
The answer is **no**. The compiler statically verifies that every field is initialized before the constructor returns, eliminating the undefined behavior that raw `MaybeUninit` would normally carry.
#### Static Field Initialization Verification
When a class has a constructor, the semantic checker (`check_class_semantics`) collects every declared field and walks the constructor body to prove each one is written to:
1. **Direct assignment tracking** — Expressions like `self.field = value` are recognized as mutations of `field`. The analyzer checks for `=` and `->` operators whose left-hand side is a `self.field` path.
2. **`&mut self.field` tracking** — Taking a mutable reference to a field (`&mut self.field`) also counts as initializing it, since the reference can only be taken if the field is being set up.
3. **Transitive method calls** — If the constructor calls `self.helper()`, the analyzer follows into `helper`'s body and tracks which fields *it* initializes. This transitively propagates through nested calls:
```mist
class Player
{
str& name;
i32 health;
pub constructor(str& name)
{
self.name = name;
self.setup_health();
}
void setup_health(&mut self)
{
self.health = 100; // Counts toward constructor's verification
}
}
```
4. **Branch intersection** — For `if`/`else`, `match`, and loops, fields must be initialized in **all** branches. If one branch initializes `x` but another does not, `x` is considered uninitialized. This ensures soundness regardless of the runtime path:
```mist
pub constructor(bool flag)
{
if flag {
self.health = 100;
} else {
self.health = 0;
}
// Both branches init health ✓
}
```
5. **Super initialization** — When a class inherits, the `_super` field is added to the required-field list. Any assignment to `super` counts:
```mist
pub constructor(str& name)
{
super = Super::new(name);
}
```
If any field is uninitialized after the full analysis, a compile-time error is reported with the field's exact source location:
```
class field `Player.health` is uninitialized
```
#### Override Validation at Compile Time
When a method uses the `override` keyword, the codegen emits a hidden test function that verifies the Deref chain at compile time:
```rust
#[allow(invalid_value)]
fn __test_vt() {
let this: &Self = &unsafe { std::mem::MaybeUninit::<Self>::zeroed().assume_init() };
let _: &Target = this; // Forces compiler to check Deref<Target = Target>
}
```
This ensures `&Self` can always deref into the base class type. If the inheritance hierarchy is invalid, the Rust compiler rejects it.
#### VTable Safety
The `_vptr` (vtable pointer) is set *twice* during construction:
1. **Before** the constructor body runs — enabling virtual dispatch inside the constructor itself
2. **After** the constructor body — in case a base-class constructor ran and overwrote the pointer
This ensures that virtual method calls work correctly even during object construction, without exposing uninitialized memory through the vtable.
#### Summary
| Risk | Mitigation |
|------|-----------|
| Uninitialized fields via `MaybeUninit` | Static field-initialization verification rejects incomplete constructors |
| UB from reading uninitialized fields | Intersection analysis ensures all branches init the same fields |
| Invalid override signatures | Compile-time Deref test validates the inheritance chain |
| Vtable corruption during construction | `_vptr` is set before and after the constructor body |
| Unsafe code in generated constructors | `#[allow(invalid_value)]` is scoped to the generated `new()` only |
The `MaybeUninit` pattern is an implementation detail of the generated code — the Mist compiler proves soundness at the language level, so the user's constructor body is safe Mist code with no manual `unsafe` annotations required.
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@@ -4,7 +4,7 @@ description: Understanding the Alpha state of Mist and our technical roadmap.
icon: TriangleAlert
---
Mist is currently in a **Volatile Alpha** stage (latest: v0.3.8-alpha.0). Our current priority is exploring **Syntax and Features**. We believe in stabilizing the developer experience and the "feel" of the language before locking in the deep architectural logic of the compiler.
Mist is currently in a **Beta** stage (latest: v0.4.0). Our current priority is exploring **Syntax and Features**. We believe in stabilizing the developer experience and the "feel" of the language before locking in the deep architectural logic of the compiler.
The compiler, transpiler, and CLI are partially bootstrapped — written in Mist itself. This gives us real-world feedback on every language design decision.
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@@ -22,6 +22,7 @@
"internals/architecture",
"internals/parsing",
"internals/semantic-analysis",
"internals/classes",
"internals/codegen",
"internals/transpiler",
"internals/builder",
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@@ -15,7 +15,7 @@ const faqs = [
{
question: "How do I install Mist?",
answer:
"Mist is distributed as a Cargo crate. Install it by running 'cargo install mist-lang@0.3.8-alpha.0'. You'll need the Rust toolchain installed. Once installed, create a new project with 'mist new my-project' and run it with 'mist run'. Check the Get Started guide for full details.",
"Mist is distributed as a Cargo crate. Install it by running 'cargo install mist-lang@0.4.0'. You'll need the Rust toolchain installed. Once installed, create a new project with 'mist new my-project' and run it with 'mist run'. Check the Get Started guide for full details.",
},
{
question: "Can I use Rust libraries with Mist?",
@@ -40,7 +40,7 @@ const faqs = [
{
question: "Is Mist production-ready?",
answer:
"Mist is currently in a Volatile Alpha stage (latest: v0.3.8-alpha.0) and is not yet production-ready. The language is evolving rapidly — the current priority is exploring syntax and features before locking in deep architectural logic. You may encounter breaking changes between releases.",
"Mist is currently in a Beta stage (latest: v0.4.0) and is not yet production-ready. The language is evolving rapidly — the current priority is exploring syntax and features before locking in deep architectural logic. You may encounter breaking changes between releases.",
},
{
question: "How does the Mist compiler work?",