typescript syntax highlighting fails when newline in function arg list and common in return type

[Naddiseo]

Issue Type: Bug

Summary: The syntax highlighting for typescript fails when there's a newline in the function parameters AND the return type has 3 levels of generics where one of them has two parameters.

The best minimal test case I can provide is the following:

type Union<A,B> = A|B;

const fn = (
// newline here
): Array<Union<Array<number>, string>>=>{
    try {
        return [[1]]
    } catch (e){
        return [[1]]
    }
}

Changing the return type's nesting seems to make it work again, but it seems that the presence of the "," and the newline in the argument list makes the coloring for the function body fail.

screenshot:

VS Code version: Code - Insiders 1.51.0-insider (f5d3ba4d61146b78f0c75c82f3f85232d3409bc1, 2020-10-09T05:34:46.257Z)
OS version: Linux x64 5.4.0-42-generic

System Info

Item	Value
CPUs	AMD Ryzen 7 2700 Eight-Core Processor (16 x 1377)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: disabled_off opengl: enabled_on protected_video_decode: unavailable_off rasterization: disabled_software skia_renderer: enabled_on video_decode: unavailable_off vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	2, 1, 1
Memory (System)	31.38GB (5.38GB free)
Process Argv	--no-sandbox
Screen Reader	no
VM	0%
DESKTOP_SESSION	gnome
XDG_CURRENT_DESKTOP	GNOME
XDG_SESSION_DESKTOP	gnome
XDG_SESSION_TYPE	wayland

Extensions: none