MoonBit Update

IDE Update

• AI Codelens now supports /generate and /fix commands.

The /generate command provides a generic interface for generating code.

The /fix command reads the current function's error information and suggests fixes.

Language Updates

• Adjusted the precedence of infix expressions and if, match, loop, while, for, try control flow expressions. These control flow expressions can no longer directly appear in positions requiring infix expressions and now require an additional layer of parentheses when nested.

For example, the syntax for if and match is:

if <infix-expr> { <expression> } [else { <expression> }]
match <infix-expr> { <match-cases> }

Since if, match, loop, while, for, try are no longer considered infix expressions, code like if if expr {} {} is now invalid:

// invalid
if if cond {a} else {b} {v} else {d}
match match expr { ... } { ... }
let a = expr1 + expr2 + if a {b} else {c} + expr3
// valid
if (if cond {a} else {b}) {v} else {d}
match (match expr { ... }) { ... }
let a = expr1 + expr2 + (if a {b} else {c}) + expr3

• JavaScript backend

  • Arrays now compile to native JS arrays, making interaction with JS more convenient.

• Standard Library API

  • Added concat and from_array functions to the String package, deprecating Array::join.
  • Added rev_concat() to the immut/list package.
  • Buffer type now includes length and is_empty functions.
  • Improved the to_json function for the Option type.

• Experimental Library API

  • x/fs package now supports the Wasm, Wasm-gc, and JS backends, including the following APIs:
    • write_string_to_file, write_bytes_to_file
    • read_file_to_string, read_file_to_bytes
    • path_exists
    • read_dir
    • create_dir
    • is_dir, is_file
    • remove_dir, remove_file

Build System Updates

• moon test -p now supports fuzzy matching. For example, moon test -p moonbitlang/core/builtin can be shortened to moon test -p mcb or moon test -p builtin.

• In moon.pkg.json, if the source field is an empty string "", it is equivalent to ".", representing the current directory.

Moondoc Update

• The documentation generator now supports package-level README files. Any README.md in the same directory as moon.pkg.json will be displayed on the package’s documentation page.