Map.addAll()

[munificent]

In my code, I recently found myself doing:

environment.forEach((key, value) => options.environment[key] = value);

Today, I find myself reviewing code that defines:

void mapAddAll(Map destination, Map source) =>
  source.forEach((key, value) => destination[key] = value);

Maybe Map should have an addAll() method that does this?

[DartBot]

This comment was originally written by @seaneagan

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Dupe of issue #2644

[lrhn]

Added Duplicate label.
Marked as being merged into #2644.