Peculiarities
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. |
@external | Changes the external name of an imported element. |
@operator, @operator.binary | Annotates a method as a binary operator overload. See below. |
@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 can only be used on class methods. The respective argument types must match the class type.
@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).
@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 |
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.
@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 |
Overloaded postfix operations do not preserve the original value automatically.
The following range limits are present as global constants for convenience:
Constant | Value |
i8.MIN_VALUE: | -128 |
i8.MAX_VALUE: | 127 |
i16.MIN_VALUE: | -32768 |
i16.MAX_VALUE: | 32767 |
i32.MIN_VALUE: | -2147483648 |
i32.MAX_VALUE: | 2147483647 |
i64.MIN_VALUE: | -9223372036854775808 |
i64.MAX_VALUE: | 9223372036854775807 |
isize.MIN_VALUE: | target specific: either |
isize.MAX_VALUE: | target specific: either |
u8.MIN_VALUE: | 0 |
u8.MAX_VALUE: | 255 |
u16.MIN_VALUE: | 0 |
u16.MAX_VALUE: | 65535 |
u32.MIN_VALUE: | 0 |
u32.MAX_VALUE: | 4294967295 |
u64.MIN_VALUE: | 0 |
u64.MAX_VALUE: | 18446744073709551615 |
usize.MIN_VALUE: | 0 |
usize.MAX_VALUE: | target specific: either |
bool.MIN_VALUE: | 0 |
bool.MAX_VALUE: | 1 |
f32.MIN_VALUE: | -3.40282347e+38 |
f32.MAX_VALUE: | 3.40282347e+38 |
f32.MIN_SAFE_INTEGER: | -16777215 |
f32.MAX_SAFE_INTEGER: | 16777215 |
f32.EPSILON: | 1.19209290e-07 |
f64.MIN_VALUE: | -1.7976931348623157e+308 |
f64.MAX_VALUE: | 1.7976931348623157e+308 |
f64.MIN_SAFE_INTEGER: | -9007199254740991 |
f64.MAX_SAFE_INTEGER: | 9007199254740991 |
f64.EPSILON: | 2.2204460492503131e-16 |
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.
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:
Constant | Description |
ASC_TARGET | 0 = WASM32, 1 = WASM64, 2 = JS (portable) |
ASC_NO_ASSERT | Whether |
ASC_MEMORY_BASE | The value of |
ASC_OPTIMIZE_LEVEL | The value of |
ASC_SHRINK_LEVEL | The value of |
ASC_FEATURE_SIGN_EXTENSION | Whether sign extension operations are enabled |
ASC_FEATURE_MUTABLE_GLOBALS | Whether mutable globals are enabled |
ASC_FEATURE_NONTRAPPING_F2I | Whether non-trapping float-to-int operations are enabled |
ASC_FEATURE_BULK_MEMORY | Whether bulk memory operations are enabled |
ASC_FEATURE_SIMD | Whether SIMD operations are enabled |
ASC_FEATURE_THREADS | Whether threads are enabled |
ASC_FEATURE_EXCEPTION_HANDLING | Whether exception handling is enabled |
ASC_FEATURE_TAIL_CALLS | Whether tail-calls are enabled |
ASC_FEATURE_REFERENCE_TYPES | Whether reference types are enabled |
For example, if a library supports SIMD but also provides a fallback:
if (ASC_FEATURE_SIMD) {// compute with SIMD operations} else {// fallback without SIMD operations}
