v0.20.0-alpha

0.20.0-alpha "Tokyoite" (2022-12-05)

Features

• Removed the event type as well as the emit keyword.
  Instead the struct type now automatically implements
  the Emittable trait and can be emitted via ctx.emit(..).

  Indexed fields can be annotated via the #indexed attribute.

  E.g.

  struct Signed {
      book_msg: String<100>
  }
  
  contract GuestBook {
      messages: Map<address, String<100>>
  
      pub fn sign(mut self, mut ctx: Context, book_msg: String<100>) {
          self.messages[ctx.msg_sender()] = book_msg
          ctx.emit(Signed(book_msg))
      }
  }
  

  (#717)

• Allow to call trait methods on types when trait is in scope

  So far traits were only useful as bounds for generic functions.
  With this change traits can also be used as illustrated with
  the following example:

  trait Double {
    fn double(self) -> u256;
  }
  
  impl Double for (u256, u256) {
    fn double(self) -> u256 {
      return (self.item0 + self.item1) * 2
    }
  }
  
  contract Example {
  
    pub fn run_test(self) {
      assert (0, 1).double() == 2
    }
  }
  

  If a call turns out to be ambigious the compiler currently asks the
  user to disambiguate via renaming. In the future we will likely
  introduce a syntax to allow to disambiguate at the callsite. (#757)

• Allow contract associated functions to be called via ContractName::function_name() syntax. (#767)

• Add enum types and match statement.

  enum can now be defined, e.g.,

  pub enum MyEnum {
      Unit
      Tuple(u32, u256, bool)
    
      fn unit() -> MyEnum {
          return MyEnum::Unit
      }
  }
  

  Also, match statement is introduced, e.g.,

  pub fn eval_enum()  -> u256{
      match MyEnum {
          MyEnum::Unit => { 
              return 0
          }
        
          MyEnum::Tuple(a, _, false) => {
              return u256(a)
          }
        
          MyEnum::Tuple(.., true) => {
              return u256(1)
          }
      }
  }
  

  For now, available patterns are restricted to

  • Wildcard(_), which matches all patterns: _
  • Named variable, which matches all patterns and binds the value to make the value usable in the arm. e.g., a, b and c in MyEnum::Tuple(a, b, c)
  • Boolean literal(true and false)
  • Enum variant. e.g., MyEnum::Tuple(a, b, c)
  • Tuple pattern. e.g., (a, b, c)
  • Struct pattern. e.g., MyStruct {x: x1, y: y1, b: true}
  • Rest pattern(..), which matches the rest of the pattern. e.g., MyEnum::Tuple(.., true)
  • Or pattern(|). e.g., MyEnum::Unit | MyEnum::Tuple(.., true)

  Fe compiler performs the exhaustiveness and usefulness checks for match statement.
  So the compiler will emit an error when all patterns are not covered or an unreachable arm are detected. (#770)

• Changed comments to use // instead of # (#776)

• Added the mut keyword, to mark things as mutable. Any variable or function parameter
  not marked mut is now immutable.

  contract Counter {
      count: u256
  
      pub fn increment(mut self) -> u256 {
          // `self` is mutable, so storage can be modified
          self.count += 1
          return self.count
      }
  }
  
  struct Point {
      pub x: u32
      pub y: u32
  
      pub fn add(mut self, _ other: Point) {
          self.x += other.x
          self.y += other.y
  
          // other.x = 1000 // ERROR: `other` is not mutable
      }
  }
  
  fn pointless() {
      let origin: Point = Point(x: 0, y: 0)
      // origin.x = 10 // ERROR: origin is not mutable
  
      let x: u32 = 10
      // x_coord = 100 // ERROR: `x_coord` is not mutable
      let mut y: u32 = 0
      y = 10 // OK
  
      let mut p: Point = origin // copies `origin`
      p.x = 10 // OK, doesn't modify `origin`
  
      let mut q: Point = p // copies `p`
      q.x = 100            // doesn't modify `p`
  
      p.add(q)
      assert p.x == 110
  }
  

  Note that, in this release, primitive type function parameters
  can't be mut. This restriction might be lifted in a future release.

  For example:

  fn increment(mut x: u256) { // ERROR: primitive type parameters can't be mut
      x += 1
  }
  

  (#777)

• The contents of the std::prelude module (currently just the Context struct)
  are now automatically used by every module, so use std::context::Context is
  no longer required. (#779)

• When the Fe compiler generates a JSON ABI file for a contract, the
  "stateMutability" field for each function now reflects whether the function can
  read or modify chain or contract state, based on the presence or absence of the
  self and ctx parameters, and whether those parameters are mutable.

  If a function doesn't take self or ctx, it's "pure".
  If a function takes self or ctx immutably, it can read state but not mutate
  state, so it's a "view"
  If a function takes mut self or mut ctx, it can mutate state, and is thus
  marked "payable".

  Note that we're following the convention set by Solidity for this field, which
  isn't a perfect fit for Fe. The primary issue is that Fe doesn't currently
  distinguish between "payable" and "nonpayable" functions; if you want a function
  to revert when Eth is sent, you need to do it manually
  (eg assert ctx.msg_value() == 0). (#783)

• Trait associated functions

  This change allows trait functions that do not take a self parameter.
  The following demonstrates a possible trait associated function and its usage:

  trait Max {
    fn max(self) -> u8;
  }
  
  impl Max for u8 {
    fn max() -> u8 {
      return u8(255)
    }
  }
  
  contract Example {
  
    pub fn run_test(self) {
      assert u8::max() == 255
    }
  }
  

  (#805)

Bugfixes

• Fix issue where calls to assiciated functions did not enforce visibility rules.

  E.g the following code should be rejected but previously wasn't:

  struct Foo {
      fn do_private_things() {
      }
  }
  
  contract Bar {
      fn test() {
          Foo::do_private_things()
      }
  }
  

  With this change, the above code is now rejected because do_private_things is not pub. (#767)

• Padding on bytes and string ABI types is zeroed out. (#769)

• Ensure traits from other modules or even ingots can be implemented (#773)

• Certain cases where the compiler would not reject pure functions
  being called on instances are now properly rejected. (#775)

• Reject calling to_mem() on primitive types in storage (#801)

• Disallow importing private type via use

  The following was previously allowed but will now error:

  use foo::PrivateStruct (#815)