Handle single-member unions imported from JSON templates

[jeskew]

Potentially a resolution to #13462

When importing a type from an ARM template, we convert the ARM schema into a Bicep IR representation so that it can be injected into the importing template. This conversion process didn't account for scenarios where the ARM allowedValues constraint was present but only allows a single value, which the Bicep type system converts to a singular literal type rather than a union.

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 8068152000)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 8068152000

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 8068152000"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 8068152000

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 8068152000"

[github-actions]

Test Results

    65 files   -     34      65 suites   - 34   22m 51s ⏱️ - 20m 43s
10 646 tests  -     19  10 645 ✅  -     19  1 💤 ±0  0 ❌ ±0 
25 182 runs   - 12 584  25 180 ✅  - 12 583  2 💤  - 1  0 ❌ ±0 

Results for commit d3269f8. ± Comparison against base commit f316152.

♻️ This comment has been updated with latest results.