"pub get" enters endless loop

[DartBot]

Originally opened as dart-lang/sdk#21522

This issue was originally filed by [email protected]

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What steps will reproduce the problem?

1. Create a new Dart project
2. Add the following dependencies to pubspec.yaml:
     polymer: ">=0.15.1+3 <0.16.0"
     paper_elements: ">=0.5.0 <0.6.0"
     args: any
     crypto: ">=0.9.0 <0.10.0"
     file_utils: ">=0.0.22 <0.1.0"
     logging: ">=0.9.1+1 <0.10.0"
     mongo_dart: ">=0.1.42 <0.2.0"
     objectory: ">=0.3.21 <0.4.0"
     shelf: any
     stack_trace: any
     watcher: ">=0.9.2 <0.10.0"
     redstone: any
3. Run "pub get"

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

Pub should get all dependencies, but instead it enters an endless loop while matching dependencies.

SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select matcher 0.11.1 from hosted
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select more 1.3.2 from hosted
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select fixnum 0.9.0 from hosted
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | selection args 0.12.1 from hosted does not match >=0.11.0 <0.12.0
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | backjump to di
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select di 3.3.1 from hosted
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | add implicit >=0.13.0 <0.15.3 pub dependency on barback
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | add implicit >=1.0.0 <2.0.0 pub dependency on source_span
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | add implicit >=0.9.1 <2.0.0 pub dependency on stack_trace
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select http 0.11.1+1 from hosted
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select http_parser 0.0.2+5 from hosted
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select matcher 0.11.1 from hosted
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select more 1.3.2 from hosted
SLVR: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * select fixnum 0.9.0 from hosted

If I add/change the following dependencies then it works just fine:
  analyzer: ">=0.15.6 <0.22.0"
  args: ">=0.11.0 <0.12.0"

What version of the product are you using?
1.7.2 and 1.8.0_dev2

On what operating system?
MacOS 10.10

What browser (if applicable)?

Please provide any additional information below.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2156198?v=3" align="left" width="48" height="48"hspace="10"> Comment by kasperl

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Added Area-Pub, Triaged labels.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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This isn't actually an endless loop, it's just the version resolution algorithm going pathological.

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Added Duplicate label.
Marked as being merged into #912.