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feat(linter): add no-unused-types rule to warn on unused type declarations #20035

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feat(linter): add no-unused-types rule to warn on unused type declarations #20035

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e6725b8
feat(linter): add no-unused-types rule to warn on unused type declara…
myaschmitz Jul 9, 2026
dc33fa7
test(linter): fix baselines and type-stringifier tests for no-unused-…
myaschmitz Jul 9, 2026
2519bbd
test(linter): update UserDefinedTypeTests for no-unused-types warnings
myaschmitz Jul 9, 2026
1f2c599
Merge main into myaschmitz/no-unused-types-linter-rule
myaschmitz Jul 14, 2026
e47a870
test(linter): verify no-unused-types code fix removes unused type
myaschmitz Jul 15, 2026
98bd31b
docs(linter): add clarifying comments to no-unused-types rule
myaschmitz Jul 16, 2026
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19 changes: 11 additions & 8 deletions src/Bicep.Core.IntegrationTests/UserDefinedTypeTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,7 @@ public void Masked_types_still_accessible_via_qualified_reference()
");

result.Should().HaveDiagnostics(new[] {
("no-unused-types", DiagnosticLevel.Warning, "Type \"string\" is declared but never used."),
("no-unused-params", DiagnosticLevel.Warning, "Parameter \"stringParam\" is declared but never used."),
});
}
Expand Down Expand Up @@ -153,8 +154,10 @@ param intParam constrainedInt
result.Should().HaveDiagnostics(new[] {
("BCP308", DiagnosticLevel.Error, "The decorator \"minLength\" may not be used on statements whose declared type is a reference to a user-defined type."),
("BCP308", DiagnosticLevel.Error, "The decorator \"maxLength\" may not be used on statements whose declared type is a reference to a user-defined type."),
("no-unused-types", DiagnosticLevel.Warning, "Type \"constrainedStringAlias\" is declared but never used."),
("BCP308", DiagnosticLevel.Error, "The decorator \"minValue\" may not be used on statements whose declared type is a reference to a user-defined type."),
("BCP308", DiagnosticLevel.Error, "The decorator \"maxValue\" may not be used on statements whose declared type is a reference to a user-defined type."),
("no-unused-types", DiagnosticLevel.Warning, "Type \"constrainedIntAlias\" is declared but never used."),
("BCP308", DiagnosticLevel.Error, "The decorator \"minLength\" may not be used on statements whose declared type is a reference to a user-defined type."),
("BCP308", DiagnosticLevel.Error, "The decorator \"maxLength\" may not be used on statements whose declared type is a reference to a user-defined type."),
("BCP308", DiagnosticLevel.Error, "The decorator \"secure\" may not be used on statements whose declared type is a reference to a user-defined type."),
Expand Down Expand Up @@ -529,7 +532,7 @@ param constrainedString string?
param sealedObject {}?
");

result.Should().NotHaveAnyDiagnostics();
result.ExcludingLinterDiagnostics().Should().NotHaveAnyDiagnostics();
}

[TestMethod]
Expand Down Expand Up @@ -746,7 +749,7 @@ public void Union_types_with_single_normalized_member_compile_without_error()
type union = 'a' | 'a'
""");

result.Should().NotHaveAnyDiagnostics();
result.ExcludingLinterDiagnostics().Should().NotHaveAnyDiagnostics();

result.Template.Should().NotBeNull();
result.Template!.Should().HaveValueAtPath("definitions.union", JToken.Parse("""
Expand All @@ -765,7 +768,7 @@ public void Nullable_union_types_do_not_include_null_in_allowed_values_constrain
type unionWithOneMember = null | 'a'
""");

result.Should().NotHaveAnyDiagnostics();
result.ExcludingLinterDiagnostics().Should().NotHaveAnyDiagnostics();

result.Template.Should().NotBeNull();
result.Template!.Should().HaveValueAtPath("definitions.union", JToken.Parse("""
Expand Down Expand Up @@ -1201,7 +1204,7 @@ public void Invalid_type_property_access_raises_diagnostic(string accessExpressi
type test2 = {{accessExpression}}
""");

result.Should().HaveDiagnostics(new[]
result.ExcludingLinterDiagnostics().Should().HaveDiagnostics(new[]
{
(expectedErrorCode, DiagnosticLevel.Error, expectedErrorMessage),
});
Expand Down Expand Up @@ -1308,7 +1311,7 @@ public void Invalid_type_index_access_raises_diagnostic(string accessExpression,
type test2 = {{accessExpression}}
""");

result.Should().HaveDiagnostics(new[]
result.ExcludingLinterDiagnostics().Should().HaveDiagnostics(new[]
{
(expectedErrorCode, DiagnosticLevel.Error, expectedErrorMessage),
});
Expand Down Expand Up @@ -1377,7 +1380,7 @@ public void Invalid_additional_properties_access_raises_diagnostic(string access
type test2 = {{accessExpression}}
""");

result.Should().HaveDiagnostics(new[]
result.ExcludingLinterDiagnostics().Should().HaveDiagnostics(new[]
{
(expectedErrorCode, DiagnosticLevel.Error, expectedErrorMessage),
});
Expand Down Expand Up @@ -1487,7 +1490,7 @@ public void Invalid_type_items_access_raises_diagnostic(string accessExpression,
type test2 = {{accessExpression}}
""");

result.Should().HaveDiagnostics(new[]
result.ExcludingLinterDiagnostics().Should().HaveDiagnostics(new[]
{
(expectedErrorCode, DiagnosticLevel.Error, expectedErrorMessage),
});
Expand Down Expand Up @@ -1654,7 +1657,7 @@ public void Parameterized_types_should_require_parameterization()
new ServiceBuilder().WithFeatureOverrides(new(TestContext)),
"""type t = resourceInput""");

result.Should().HaveDiagnostics([
result.ExcludingLinterDiagnostics().Should().HaveDiagnostics([
("BCP384", DiagnosticLevel.Error, """The "resourceInput<ResourceTypeIdentifier>" type requires 1 argument(s)."""),
]);
}
Expand Down
1 change: 1 addition & 0 deletions src/Bicep.Core.Samples/Files/baselines/Imports_LF/main.diagnostics.bicep
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ var aliasedBar = mod2.foo
//@[04:14) [no-unused-vars (Warning)] Variable "aliasedBar" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-vars) |aliasedBar|

type fizzes = fizz[]
//@[05:11) [no-unused-types (Warning)] Type "fizzes" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |fizzes|

param fizzParam mod2.fizz
//@[06:15) [no-unused-params (Warning)] Parameter "fizzParam" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-params) |fizzParam|
Expand Down
20 changes: 20 additions & 0 deletions src/Bicep.Core.Samples/Files/baselines/InvalidResourceDerivedTypes_LF/main.diagnostics.bicep
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Original file line number Diff line number Diff line change
@@ -1,45 +1,60 @@
type invalid1 = resourceInput
//@[005:013) [no-unused-types (Warning)] Type "invalid1" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid1|
//@[016:029) [BCP384 (Error)] The "resourceInput<ResourceTypeIdentifier>" type requires 1 argument(s). (bicep https://aka.ms/bicep/core-diagnostics#BCP384) |resourceInput|

type invalid2 = resourceInput<>
//@[005:013) [no-unused-types (Warning)] Type "invalid2" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid2|
//@[029:031) [BCP071 (Error)] Expected 1 argument, but got 0. (bicep https://aka.ms/bicep/core-diagnostics#BCP071) |<>|

type invalid3 = resourceInput<'abc', 'def'>
//@[005:013) [no-unused-types (Warning)] Type "invalid3" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid3|
//@[029:043) [BCP071 (Error)] Expected 1 argument, but got 2. (bicep https://aka.ms/bicep/core-diagnostics#BCP071) |<'abc', 'def'>|
type invalid4 = resourceInput<hello>
//@[005:013) [no-unused-types (Warning)] Type "invalid4" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid4|
//@[030:035) [BCP070 (Error)] Argument of type "{ bar: Astronomer.Astro/organizations }" is not assignable to parameter of type "string". (bicep https://aka.ms/bicep/core-diagnostics#BCP070) |hello|
type invalid5 = resourceInput<'Microsoft.Storage/storageAccounts'>
//@[005:013) [no-unused-types (Warning)] Type "invalid5" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid5|
//@[030:065) [BCP029 (Error)] The resource type is not valid. Specify a valid resource type of format "<type-name>@<apiVersion>". (bicep https://aka.ms/bicep/core-diagnostics#BCP029) |'Microsoft.Storage/storageAccounts'|
type invalid6 = resourceInput<'Microsoft.Storage/storageAccounts@'>
//@[005:013) [no-unused-types (Warning)] Type "invalid6" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid6|
//@[030:066) [BCP029 (Error)] The resource type is not valid. Specify a valid resource type of format "<type-name>@<apiVersion>". (bicep https://aka.ms/bicep/core-diagnostics#BCP029) |'Microsoft.Storage/storageAccounts@'|
type invalid7 = resourceInput<'Microsoft.Storage/storageAccounts@hello'>
//@[005:013) [no-unused-types (Warning)] Type "invalid7" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid7|
//@[030:071) [BCP029 (Error)] The resource type is not valid. Specify a valid resource type of format "<type-name>@<apiVersion>". (bicep https://aka.ms/bicep/core-diagnostics#BCP029) |'Microsoft.Storage/storageAccounts@hello'|
type invalid8 = resourceInput<'notARealNamespace:Microsoft.Storage/storageAccounts@2022-09-01'>
//@[005:013) [no-unused-types (Warning)] Type "invalid8" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid8|
//@[030:094) [BCP208 (Error)] The specified namespace "notARealNamespace" is not recognized. Specify a resource reference using one of the following namespaces: "az", "sys". (bicep https://aka.ms/bicep/core-diagnostics#BCP208) |'notARealNamespace:Microsoft.Storage/storageAccounts@2022-09-01'|
type invalid9 = resourceInput<':Microsoft.Storage/storageAccounts@2022-09-01'>
//@[005:013) [no-unused-types (Warning)] Type "invalid9" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid9|
//@[030:077) [BCP029 (Error)] The resource type is not valid. Specify a valid resource type of format "<type-name>@<apiVersion>". (bicep https://aka.ms/bicep/core-diagnostics#BCP029) |':Microsoft.Storage/storageAccounts@2022-09-01'|
type invalid10 = resourceInput<'abc' 'def'>
//@[005:014) [no-unused-types (Warning)] Type "invalid10" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid10|
//@[030:043) [BCP071 (Error)] Expected 1 argument, but got 2. (bicep https://aka.ms/bicep/core-diagnostics#BCP071) |<'abc' 'def'>|
//@[037:037) [BCP236 (Error)] Expected a new line or comma character at this location. (bicep https://aka.ms/bicep/core-diagnostics#BCP236) ||
type invalid11 = resourceInput<123>
//@[005:014) [no-unused-types (Warning)] Type "invalid11" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid11|
//@[031:034) [BCP070 (Error)] Argument of type "123" is not assignable to parameter of type "string". (bicep https://aka.ms/bicep/core-diagnostics#BCP070) |123|
type invalid12 = resourceInput<resourceGroup()>
//@[005:014) [no-unused-types (Warning)] Type "invalid12" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |invalid12|
//@[030:047) [BCP071 (Error)] Expected 1 argument, but got 2. (bicep https://aka.ms/bicep/core-diagnostics#BCP071) |<resourceGroup()>|
//@[044:044) [BCP236 (Error)] Expected a new line or comma character at this location. (bicep https://aka.ms/bicep/core-diagnostics#BCP236) ||
//@[045:045) [BCP243 (Error)] Parentheses must contain exactly one expression. (bicep https://aka.ms/bicep/core-diagnostics#BCP243) ||

type thisIsWeird = resourceInput</*
//@[005:016) [no-unused-types (Warning)] Type "thisIsWeird" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |thisIsWeird|
//@[019:098) [BCP394 (Error)] Resource-derived type expressions must dereference a property within the resource body. Using the entire resource body type is not permitted. (bicep https://aka.ms/bicep/core-diagnostics#BCP394) |resourceInput</*\n*/'Astronomer.Astro/organizations@2023-08-01-preview'\n/// >\n>|
*/'Astronomer.Astro/organizations@2023-08-01-preview'
/// >
>

type interpolated = resourceInput<'Microsoft.${'Storage'}/storageAccounts@2022-09-01'>
//@[005:017) [no-unused-types (Warning)] Type "interpolated" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |interpolated|
//@[034:085) [BCP032 (Error)] The value must be a compile-time constant. (bicep https://aka.ms/bicep/core-diagnostics#BCP032) |'Microsoft.${'Storage'}/storageAccounts@2022-09-01'|

@sealed()
//@[000:009) [BCP386 (Error)] The decorator "sealed" may not be used on statements whose declared type is a reference to a resource-derived type. (bicep https://aka.ms/bicep/core-diagnostics#BCP386) |@sealed()|
type shouldNotBeSealable = resourceInput<'Microsoft.Storage/storageAccounts@2022-09-01'>
//@[005:024) [no-unused-types (Warning)] Type "shouldNotBeSealable" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |shouldNotBeSealable|
//@[027:088) [BCP394 (Error)] Resource-derived type expressions must dereference a property within the resource body. Using the entire resource body type is not permitted. (bicep https://aka.ms/bicep/core-diagnostics#BCP394) |resourceInput<'Microsoft.Storage/storageAccounts@2022-09-01'>|

type hello = {
Expand All @@ -50,14 +65,19 @@ type hello = {
}

type typoInPropertyName = resourceInput<'Microsoft.Storage/storageAccounts@2023-01-01'>.nom
//@[005:023) [no-unused-types (Warning)] Type "typoInPropertyName" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |typoInPropertyName|
//@[088:091) [BCP053 (Error)] The type "Microsoft.Storage/storageAccounts" does not contain property "nom". Available properties include "apiVersion", "asserts", "dependsOn", "eTag", "extendedLocation", "id", "identity", "kind", "location", "managedBy", "managedByExtended", "name", "plan", "properties", "scale", "sku", "tags", "type", "zones". (bicep https://aka.ms/bicep/core-diagnostics#BCP053) |nom|
type typoInPropertyName2 = resourceInput<'Microsoft.KeyVault/vaults@2022-07-01'>.properties.accessPolicies[*].tenatId
//@[005:024) [no-unused-types (Warning)] Type "typoInPropertyName2" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |typoInPropertyName2|
//@[110:117) [BCP083 (Error)] The type "AccessPolicyEntry" does not contain property "tenatId". Did you mean "tenantId"? (bicep https://aka.ms/bicep/core-diagnostics#BCP083) |tenatId|
type typoInPropertyName3 = resourceInput<'Microsoft.KeyVault/vaults@2022-07-01'>.properties[*].accessPolicies.tenantId
//@[005:024) [no-unused-types (Warning)] Type "typoInPropertyName3" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |typoInPropertyName3|
//@[091:094) [BCP390 (Error)] The array item type access operator ('[*]') can only be used with typed arrays. (bicep https://aka.ms/bicep/core-diagnostics#BCP390) |[*]|
type typoInPropertyName4 = resourceInput<'Microsoft.Web/customApis@2016-06-01'>.properties.connectionParameters.*.tyype
//@[005:024) [no-unused-types (Warning)] Type "typoInPropertyName4" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |typoInPropertyName4|
//@[114:119) [BCP083 (Error)] The type "ConnectionParameter" does not contain property "tyype". Did you mean "type"? (bicep https://aka.ms/bicep/core-diagnostics#BCP083) |tyype|
type typoInPropertyName5 = resourceInput<'Microsoft.Web/customApis@2016-06-01'>.properties.*.connectionParameters.type
//@[005:024) [no-unused-types (Warning)] Type "typoInPropertyName5" is declared but never used. (bicep core linter https://aka.ms/bicep/linter-diagnostics#no-unused-types) |typoInPropertyName5|
//@[091:092) [BCP389 (Error)] The type "CustomApiPropertiesDefinition" does not declare an additional properties type. (bicep https://aka.ms/bicep/core-diagnostics#BCP389) |*|

module mod 'modules/mod.json' = {
Expand Down
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