Keywords¶

Reserved keywords in Desi. A reserved word cannot be used as a variable, parameter, or function name.

This list matches keywordToken in compiler/internal/lex/scanner.go.

Declaration Keywords¶

Keyword	Description
`let`	Bind a variable — immutable unless followed by `mut`
`mut`	Mark a binding or field mutable (`let mut x = 1`)
`const`	Compile-time constant
`static`	Belongs to the class rather than to any one instance
`def`	Function definition
`lambda`	Anonymous function expression
`class`	Class definition
`struct`	Struct definition
`enum`	Enum definition
`trait`	Trait definition
`impl`	Trait implementation
`type`	Type alias
`pub`	Public visibility

There is no var

Mutability is spelled let mut, not var.

Control Flow Keywords¶

Keyword	Description
`if`	Conditional
`elif`	Else if
`else`	Else branch
`for`	For loop
`while`	While loop
`match`	Pattern matching
`break`	Leave the innermost loop
`continue`	Skip to the next iteration of the innermost loop
`return`	Return value
`pass`	No-op statement
`defer`	Run a statement when the scope exits, in reverse order
`using`	Resource management — scope-bound cleanup

There is no loop:

break and continue apply to the innermost enclosing for or while. For an unbounded loop, write while true:. Using either outside a loop is DTE0130.

Match arms take no case

Arms are written as Pattern: body directly. case is not reserved, and is not used by match — it appears only inside a select: block, along with default, as part of that statement's syntax.

Error Handling Keywords¶

Keyword	Description
`try`	Begin a block whose exceptions are handled
`except`	Handle a raised exception
`finally`	Run whether or not an exception was raised
`raise`	Raise an exception
`assert`	Check that a condition holds at runtime

Concurrency Keywords¶

Keyword	Description
`async`	Async function
`await`	Await an async result
`spawn`	Start a concurrent task
`select`	Wait on multiple channel operations

Boolean and Value Keywords¶

Keyword	Description
`true`	Boolean true
`false`	Boolean false
`none`	The absence of a value
`and`	Logical AND
`or`	Logical OR
`not`	Logical NOT

Parameter Modes¶

Keyword	Description
`ref`	Pass by reference, read-only
`inout`	Pass by reference, and the caller sees writes

Other Keywords¶

Keyword	Description
`in`	Membership and iteration
`is`	Type and variant check
`unsafe`	Permit operations that bypass Desi's guarantees, such as `@extern` calls
`import`	Module import
`from`	Import from a module
`as`	Alias

Not reserved¶

self and cls are ordinary parameter names, not keywords. They are meaningful by position — the first parameter of a method — and the compiler supplies self for you if you leave it off. Either may be used as a normal variable name, though doing so is confusing and best avoided.

__new__ is likewise a name rather than a keyword. See Classes for the constructor it declares.