Compiler "assertion failed" when using unknown type

[vincent-tr]

Expected behavior

Get a clear error that the type is unknown. Possibly other related errors when using the type.

Steps to reproduce

Compile the following code:

class MyClass {
  get value(): UnknownType {
  }
}

export function test(obj: MyClass): void {
  obj.value;
}

On the playground https://www.assemblyscript.org/editor.html I get the "assertion failed" in the browser's console:

AssertionError: assertion failed
    at i.assert (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:722100)
    at f.compilePropertyAccessExpression (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:317653)
    at f.compileExpression (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:236891)
    at f.compileExpressionStatement (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:225012)
    at f.compileStatement (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:221342)
    at f.compileStatements (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:222370)
    at f.compileFunctionBody (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:211588)
    at f.compileFunction (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:210572)
    at f.compileElement (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:202495)
    at f.compileExports (https://cdn.jsdelivr.net/npm/assemblyscript@0.18.12/dist/assemblyscript.js:7:203235)

[dcodeIO]

Thanks, should be fixed :)