Supporting constructing Maps from Lists of key/value pairs

[DartBot]

This issue was originally filed by @MarkBennett

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What steps will reproduce the problem?

1. Generate a List of key/value pairs (such as by parsing a query string)
2. Attempt to create a new Map from the list.
3. Fail.

What is the expected output? What do you see instead?

    I would expect the Map to include a constructor that could construct a Map from a List of key/value pairs similair to the Hash constructor in Ruby (http://rdoc.info/stdlib/core/1.9.3/Hash.%5B%5D)

What version of the product are you using? On what operating system?

Version 0.1.0.201204121423, Build 6479
Dart SDK version 6478, Dartium version

Please provide any additional information below.

[madsager]

Added Area-Library, Triaged labels.

[DartBot]

This comment was originally written by @seaneagan

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This would involve introducing some sort of Pair<K, V> interface, so this could then be done by having Map<K, V> extend Collection<Pair<K, V>> (see issue #326 discussion), and then changing the parameter type of the Map.from constructor:

Map.from(Collection<Pair<K, V>>);

[DartBot]

This comment was originally written by ladicek@gmail.com

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This would involve introducing some sort of Pair<K, V>

Not necessarily. I think that the original poster wants (and the link to RDoc confirms) a constructor that takes a list, which contains keys and values interleaved, like this:

Map<int, String> m = new Map.fromInterleaved(1, "a", 2, "b");

"fromInterleaved" isn't exactly the best name, but I think that it also isn't the best idea -- especially when full Map literals come (the current limitation to String keys is kinda annoying, really).

[lrhn]

We don't particularly want to introduce pairs of keys/values.
We have Map.fromIterable which would work:
  new Map.fromIterable(pairList, (p) => p.first, (p) => p.second)
or if you don't keep the key and value in the same list:
  new Map.fromIterables(keys, values)

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Added NotPlanned label.