No, that match will fail as soon as you pass something into the function that is not a map, or if it is a map and does not have a key :name.

iex(1)> defmodule Greeter1 do
...(1)>   def hello(%{name: person_name}) do
...(1)>     IO.puts "Hello, " <> person_name
...(1)>   end
...(1)> end
{:module, Greeter1,
 <<70, 79, 82, 49, 0, 0, 4, 248, 66, 69, 65, 77, 65, 116, 85, 56, 0, 0, 0, 162,
   0, 0, 0, 18, 15, 69, 108, 105, 120, 105, 114, 46, 71, 114, 101, 101, 116,
   101, 114, 49, 8, 95, 95, 105, 110, 102, 111, ...>>, {:hello, 1}}
iex(2)> Greeter1.hello(1)
** (FunctionClauseError) no function clause matching in Greeter1.hello/1

    The following arguments were given to Greeter1.hello/1:

        # 1
        1

    iex:2: Greeter1.hello/1
iex(2)> Greeter1.hello(%{})
** (FunctionClauseError) no function clause matching in Greeter1.hello/1

    The following arguments were given to Greeter1.hello/1:

        # 1
        %{}

    iex:2: Greeter1.hello/1
iex(2)> Greeter1.hello(%{sur_name: "Random"})
** (FunctionClauseError) no function clause matching in Greeter1.hello/1

    The following arguments were given to Greeter1.hello/1:

        # 1
        %{sur_name: "Random"}

    iex:2: Greeter1.hello/1
iex(2)> Greeter1.hello(%{name: "Random"})
Hello, Random
:ok
iex(3)> Greeter1.hello(%{name: "Random", sur_name: "Guy"})
Hello, Random
:ok