# Peculiarities

Special features that exist for internal implementation purposes or are otherwise nice to have.

# Annotations

Decorators work more like actual compiler annotations in AssemblyScript.

Annotation	Description
`@inline`	Requests inlining of a constant or function.
`@lazy`	Requests lazy compilation of a variable. Useful to avoid unnecessary globals.
`@global`	Registers an element to be part of the global scope.
`@final`	Annotates a class as final, that is it cannot be subclassed.
`@unmanaged`	Annotates a class as not tracked by GC, essentially C structs.
`@external`	Changes the external name of an imported element. `@external(module, name)` changes both the module and element name, `@external(name)` changes the element name only.
`@operator`	Annotates a method as a binary operator overload. See below.
`@operator.binary`	Alias of `@operator`.
`@operator.prefix`	Annotates a method as a unary prefix operator overload. See below.
`@operator.postfix`	Annotates a method as a unary postfix operator overload. See below.

Custom decorators can be given meaning by using a transform.

# Operator overloads

Operator overloads can only be used on class methods. The respective argument types must match the class type.

# Binary operations

@operator(OP)
static __op(left: T, right :T): T { ... }

@operator(OP)
__op(right: T): T  { ... }

OP	Description
`"[]"`	Checked indexed get
`"[]="`	Checked indexed set
`"{}"`	Unchecked indexed get
`"{}="`	Unchecked indexed set
`"=="`	Equality
`"!="`	Inequality
`">"`	Greater than
`">="`	Greater than or equal
`"<"`	Less than
`"<="`	Less than or equal
`">>"`	Arithmetic right shift
`">>>"`	Logical right shift
`"<<"`	Left shift
`"&"`	Bitwise AND
`"\|"`	Bitwise OR
`"^"`	Bitwise XOR
`"+"`	Addition
`"-"`	Subtraction
`"*"`	Multiplication
`"/"`	Division
`"**"`	Exponentiation
`"%"`	Remainder

The === operation cannot be overloaded (is identity equality).

# Unary prefix operations

@operator.prefix(OP)
static __op(self: T): T { ... }

@operator.prefix(OP)
__op(): T { ... }

OP	Description	Notes
`"!"`	Logical NOT
`"~"`	Bitwise NOT
`"+"`	Unary plus
`"-"`	Unary negation
`"++"`	Prefix increment	Instance overload reassigns
`"--"`	Prefix decrement	Instance overload reassigns

TIP

Note that increment and decrement overloads can have slightly different semantics. If the overload is declared as an instance method, on ++a the compiler does emit code that reassigns the resulting value to a while if the overload is declared static, the overload behaves like any other overload, skipping the otherwise implicit assignment.

# Unary postfix operations

@operator.postfix(OP)
static __op(self: T): T { ... }

@operator.postfix(OP)
__op(): T { ... }

OP	Description	Notes
`"++"`	Postfix increment	Instance overload reassigns
`"--"`	Postfix decrement	Instance overload reassigns

TIP

Overloaded postfix operations do not preserve the original value automatically.

# Range limits

The following range limits are present as global constants for convenience:

const i8.MIN_VALUE: i8 = -128
const i8.MAX_VALUE: i8 = 127

const i16.MIN_VALUE: i16 = -32768
const i16.MAX_VALUE: i16 = 32767

const i32.MIN_VALUE: i32 = -2147483648
const i32.MAX_VALUE: i32 = 2147483647

const i64.MIN_VALUE: i64 = -9223372036854775808
const i64.MAX_VALUE: i64 = 9223372036854775807

const isize.MIN_VALUE: isize // WASM32: i32.MIN_VALUE, WASM64: i64.MIN_VALUE
const isize.MAX_VALUE: isize // WASM32: i32.MAX_VALUE, WASM64: i64.MAX_VALUE

const u8.MIN_VALUE: u8 = 0
const u8.MAX_VALUE: u8 = 255

const u16.MIN_VALUE: u16 = 0
const u16.MAX_VALUE: u16 = 65535

const u32.MIN_VALUE: u32 = 0
const u32.MAX_VALUE: u32 = 4294967295

const u64.MIN_VALUE: u64 = 0
const u64.MAX_VALUE: u64 = 18446744073709551615

const usize.MIN_VALUE: usize = 0
const usize.MAX_VALUE: usize // WASM32: u32.MAX_VALUE, WASM64: u64.MAX_VALUE

const bool.MIN_VALUE: bool = 0
const bool.MAX_VALUE: bool = 1

const f32.MIN_VALUE: f32 = -3.40282347e+38
const f32.MAX_VALUE: f32 = 3.40282347e+38
const f32.MIN_NORMAL_VALUE: f32 = 1.17549435e-38
const f32.MIN_SAFE_INTEGER: f32 = -16777215
const f32.MAX_SAFE_INTEGER: f32 = 16777215
const f32.EPSILON: f32 = 1.19209290e-07

const f64.MIN_VALUE: f64 = -1.7976931348623157e+308
const f64.MAX_VALUE: f64 = 1.7976931348623157e+308
const f64.MIN_NORMAL_VALUE: f64 = 2.2250738585072014e-308
const f64.MIN_SAFE_INTEGER: f64 = -9007199254740991
const f64.MAX_SAFE_INTEGER: f64 = 9007199254740991
const f64.EPSILON: f64 = 2.2204460492503131e-16

# Tree-shaking

# Module-level

The compiler only compiles elements reachable from the entry file and ignores everything that remains unused. This is very similar to a JavaScript VM's behavior when running a JavaScript file, but unlike in TypeScript it also affects checking of types. Helps to reduce compilation times and binary sizes significantly.

# Branch-level

In addition to module-level tree-shaking, the compiler ignores branches that it can prove won't be taken. Works with constants, built-ins that compile to a constant, expressions that can be precomputed to a constant, plus the following globals to detect specific compiler flags or features:

```
const ASC_TARGET: i32
```
Indicates the compilation target. Possible values are 0 = JS (portable), 1 = WASM32, 2 = WASM64.
```
const ASC_NO_ASSERT: bool
```
Whether --noAssert has been set.
```
const ASC_MEMORY_BASE: usize
```
The value of --memoryBase.
```
const ASC_OPTIMIZE_LEVEL: i32
```
The value of --optimizeLevel. Possible values are 0, 1, 2 and 3.
```
const ASC_SHRINK_LEVEL: i32
```
The value of --shrinkLevel. Possible values are 0, 1 and 2.
```
const ASC_LOW_MEMORY_LIMIT: i32
```
The value of --lowMemoryLimit.
```
const ASC_EXPORT_RUNTIME: i32
```
Whether --exportRuntime has been set.

const ASC_FEATURE_SIGN_EXTENSION: bool
const ASC_FEATURE_MUTABLE_GLOBALS: bool
const ASC_FEATURE_NONTRAPPING_F2I: bool
const ASC_FEATURE_BULK_MEMORY: bool
const ASC_FEATURE_SIMD: bool
const ASC_FEATURE_THREADS: bool
const ASC_FEATURE_EXCEPTION_HANDLING: bool
const ASC_FEATURE_TAIL_CALLS: bool
const ASC_FEATURE_REFERENCE_TYPES: bool
const ASC_FEATURE_MULTI_VALUE: bool
const ASC_FEATURE_GC: bool
const ASC_FEATURE_MEMORY64: bool

Whether the respective feature is enabled.

For example, if a library supports SIMD but also wants to provide a fallback when being compiled without SIMD support:

if (ASC_FEATURE_SIMD) {
  // compute with SIMD operations
} else {
  // fallback without SIMD operations
}

```
const ASC_WASI: i32
```
A constant only being defined when WASI bindings are used via import "wasi". Can be checked with isDefined(ASC_WASI).

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