Variable extraction changes outcome when inserting into dictionary

bug.gd

extends Node

func _ready() -> void:
	var values

  # Bad setup: prints {a:40, b:42}
	values = { "a": 0, "b": 0 }
	for idx in range(0, 100):
		values["a" if randf() > 0.9 else "b"] += 1
	print(values)

  # Good setup: prints {a:8, b:92}
	values = { "a": 0, "b": 0 }
	for idx in range(0, 100):
		var value = "a" if randf() > 0.9 else "b"
		values[value] += 1
	print(values)