TrustedHostMiddleware Doesn't handle IPv6 properly

[gopackgo90]

Say I have the below Starlette app,

# main.py
from starlette.applications import Starlette
from starlette.middleware import Middleware
from starlette.middleware.trustedhost import TrustedHostMiddleware
from starlette.responses import JSONResponse
from starlette.routing import Route


async def homepage(request):
    return JSONResponse({'hello': 'world'})

routes = [
    Route("/", endpoint=homepage)
]

middleware = [
    Middleware(TrustedHostMiddleware, allowed_hosts=["[::1]"])
]

app = Starlette(debug=True, routes=routes, middleware=middleware)

and run it with uvicorn main:app --host '::1'. When I go to http://[::1]:8000 in my browser, I get the "Invalid host header" response. This appears to be because Starlette is thinking the host is "[" based on the splitting logic in the middleware,

starlette/starlette/middleware/trustedhost.py

Line 40 in 70a3bd4

host = headers.get("host", "").split(":")[0]

.
When I remove the TrustedHostMiddleware, I get the hello world response as expected.