Assignment to built-in function crashes the compiler #2202

▌ Whoops, the AssemblyScript compiler has crashed during compile :-(
▌ 
▌ Here is the stack trace hinting at the problem, perhaps it's useful?
▌ 
▌ AssertionError: assertion failed
▌     at assert (D:\assemblyscript\std\portable\index.js:200:11)
▌     at Compiler.ensureRuntimeFunction (D:\assemblyscript\src\compiler.ts:2074:5)
▌     at Compiler.compileIdentifierExpression (D:\assemblyscript\src\compiler.ts:7866:27)
▌     at Compiler.compileExpression (D:\assemblyscript\src\compiler.ts:3511:21)
▌     at Compiler.compileGlobal (D:\assemblyscript\src\compiler.ts:1180:25)
▌     at Compiler.compileTopLevelStatement (D:\assemblyscript\src\compiler.ts:2140:20)
▌     at Compiler.compileFile (D:\assemblyscript\src\compiler.ts:1111:12)
▌     at Compiler.compile (D:\assemblyscript\src\compiler.ts:486:14)
▌     at Object.compile (D:\assemblyscript\src\index.ts:280:32)
▌     at D:\assemblyscript\cli\asc.js:902:31
▌     at measure (D:\assemblyscript\cli\asc.js:1409:3)
▌     at Object.main (D:\assemblyscript\cli\asc.js:900:24)
▌     at runTest (D:\assemblyscript\tests\compiler.js:178:7)
▌     at Array.forEach (<anonymous>)
▌     at D:\assemblyscript\tests\compiler.js:557:16
▌ 
▌ If it refers to the dist files, try to 'npm install source-map-support' and
▌ run again, which should then show the actual code location in the sources.
▌ 
▌ If you see where the error is, feel free to send us a pull request. If not,
▌ please let us know: https://github.com/AssemblyScript/assemblyscript/issues
▌ 
▌ Thank you!