v2.27.0 - Dart setters

Dart setters

set name(T value) { … } is implemented. It was the last accessor with no
support at all — no grammar rule, no AST node, no dispatch. 2.26.0 turned it
from a silent misparse (into a method named name returning a type named set)
into a clean parse error; it now works.

Parsed on classes and extensions, with a typed or untyped parameter and an arrow
or block body:

class Box {
  int _v = 0;
  int get value => _v;
  set value(int x) { _v = x; }
  set scaled(v) => _v = v * 10;
}

A setter runs on every write position — obj.x = v, this.x = v, and an
unqualified x = v inside the class, the write-side mirror of an unqualified
getter read. A real variable in scope still wins, so a setter's own parameter
cannot re-enter it. Compound assignment (obj.x += 1) reads through the getter
when there is one and falls back to the backing field; ??= short-circuits, so
the setter does not run when the current value is non-null. Inherited and
overridden setters resolve through the superclass chain, and extension setters
work like extension getters.

Only Dart generates setters. Every other target refuses with
UnsupportedSyntaxError, and Wasm refuses rather than letting an assignment
silently write the backing field instead of running the setter body.

An arrow-bodied setter regenerates as an arrow: emitting it as a block would
produce set x(v) { return …; }, which Dart rejects because a setter returns
void. The generated output is verified with the real dart analyze.

Fixed: getters silently dropped when translating to Python, Go and Lua

Those three generators never iterated the class's accessors, so a class with a
getter translated to any of them lost the accessor entirely while the method
bodies kept referencing the property — broken code that looked fine, rather than
the honest UnsupportedSyntaxError Java/C#/JS/TS already produced. They now
refuse, like the others.

Fixed: ASTBlock.set dropped setters

It copied functions, getters and statements, so every class member survived the
temporary parse block except the new ones.

Still missing

For getters and setters alike: static accessors, top-level accessors, and an
unqualified read of a getter (return value; inside a method — this.value
works). Kotlin generates getters but not setters.

Full changelog: https://github.com/ApolloVM/apollovm_dart/blob/v2.27.0/CHANGELOG.md