feat(linter): add no-unused-types rule to warn on unused type declarations

[myaschmitz]

Description

Adds a new linter rule no-unused-types that emits a warning when a user-defined type is declared but never referenced, mirroring the existing no-unused-vars and no-unused-params rules. Types marked with @export() are excluded, and a Remove unused type quick-fix is provided.

Fixes #11876

Example Usage

Given the following Bicep file:

type usedType = {
  name: string
}

type unusedType = string   // warning: Type "unusedType" is declared but never used.

param person usedType
output personName string = person.name

The linter reports:

main.bicep(5,6) : Warning no-unused-types: Type "unusedType" is declared but never used. [https://aka.ms/bicep/linter-diagnostics#no-unused-types]

The rule defaults to warning level and can be configured in bicepconfig.json.

Changes

• NoUnusedTypesRule.cs - new rule (auto-discovered via the linter rule source generator).
• CoreResources.resx / .Designer.cs - description and message resource strings.
• bicepconfig.schema.json - schema entry so the rule is configurable with IntelliSense.
• NoUnusedTypesRuleTests.cs - unit tests (used/unused/exported/type-alias-chain/syntax-error cases).

Note: Documentation lives in the separate Microsoft Learn docs repo (the aka.ms/bicep/linter-diagnostics#no-unused-types anchor). Companion docs PR (internal): MicrosoftDocs/azure-docs-pr#318158 - adds the linter-rule-no-unused-types.md page, the linter.md table row, and the toc.yml entry.

Checklist

• I have read and adhere to the contribution guide.

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 29538039388)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 29538039388

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 29538039388"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 29538039388

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 29538039388"

[anthony-c-martin]

Could you also add a test to verify the code fix works?

See

bicep/src/Bicep.Core.UnitTests/Diagnostics/LinterRuleTests/NoModuleNameRuleTests.cs

Lines 52 to 62 in 1f2c599

	[TestMethod]
	public void Codefix_removes_name_property() => AssertCodeFix("""
	module foo 'br/public:avm/res/network/virtual-network:0.1.8' = {
	na|me: 'foo'
	params: {}
	}
	""", """
	module foo 'br/public:avm/res/network/virtual-network:0.1.8' = {
	params: {}
	}
	""");

for an example of how to do this.