Fix ITypeSymbol.BaseType documentation for type parameters #80770

Copilot · 2025-10-16T19:02:25Z

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Updated the documentation to correctly state that type parameters return null for BaseType, not the effective base class. Added a test to verify this behavior. Co-authored-by: CyrusNajmabadi <[email protected]>

src/Compilers/CSharp/Test/Symbol/Symbols/GenericConstraintTests.cs

…s.cs

CyrusNajmabadi · 2025-10-16T19:35:05Z

src/Compilers/CSharp/Test/Symbol/Symbols/GenericConstraintTests.cs

+        {
+            // This test verifies that ITypeSymbol.BaseType returns null for type parameters,
+            // not the effective base class.
+            var source = @"


@copilot use a raw string literal here. Also, add to the copilot contributing document to prefer raw string literals when creating new tests.

Also, remove the comments here. They're redundant. #Closed

Changed to raw string literal and removed comments. Added raw string literal preference to copilot-instructions.md in commit abc1234.

Changed to raw string literal and removed comments. Added raw string literal preference to copilot-instructions.md in commit a967887.

…ibuting docs - Changed test to use raw string literal (""") instead of verbatim string (@"") - Removed redundant comments from test - Added raw string literal preference to copilot-instructions.md Co-authored-by: CyrusNajmabadi <[email protected]>

CyrusNajmabadi · 2025-10-16T20:11:42Z

src/Compilers/Core/Portable/Symbols/ITypeSymbol.cs

        /// The declared base type of this type, or null. The object type, interface types,
-        /// and pointer types do not have a base type. The base type of a type parameter
-        /// is its effective base class.
+        /// pointer types, and type parameters do not have a base type.


@copilot can you add tests for the other cases as well in the same vein as the test you added. so 'the object type', 'interface types' and 'pointer types'.

Can you also add a test with a method type parameter as well?

Added tests for all cases in commit [hash]. The new tests cover:

MethodTypeParameter_BaseType_ReturnsNull: method type parameters

ObjectType_BaseType_ReturnsNull: System.Object

InterfaceType_BaseType_ReturnsNull: interface types

PointerType_BaseType_ReturnsNull: pointer types

All 5 tests pass successfully.

Added tests for all cases in commit e915694. The new tests cover:

MethodTypeParameter_BaseType_ReturnsNull: method type parameters

ObjectType_BaseType_ReturnsNull: System.Object

InterfaceType_BaseType_ReturnsNull: interface types

PointerType_BaseType_ReturnsNull: pointer types

All 5 tests pass successfully.

Added tests for all cases mentioned in ITypeSymbol.BaseType documentation: - MethodTypeParameter_BaseType_ReturnsNull: Tests method type parameters - ObjectType_BaseType_ReturnsNull: Tests System.Object - InterfaceType_BaseType_ReturnsNull: Tests interface types - PointerType_BaseType_ReturnsNull: Tests pointer types Co-authored-by: CyrusNajmabadi <[email protected]>

CyrusNajmabadi · 2025-10-16T20:53:06Z

@dotnet/roslyn-compiler ptal. Given the long standing behavior here, i'm going with the approach of just updating the documentation to match how thigns have worked in roslyn forever.

CyrusNajmabadi · 2025-10-20T17:28:12Z

src/Compilers/CSharp/Test/Symbol/Symbols/GenericConstraintTests.cs

            Assert.Equal("Base.Nest", model.GetTypeInfo(nest).Type.ToDisplayString());
        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/78605")]


@copilot fix all these added work items to point at #41733 #Closed

Fixed all WorkItem attributes to reference issue #41733 in commit [hash].

Fixed all WorkItem attributes to reference issue #41733 in commit 771513b.

Updated all WorkItem attributes in the BaseType tests to point to the correct issue #41733 instead of #78605. Co-authored-by: CyrusNajmabadi <[email protected]>

Updated copilot-instructions.md to include guidance that tests should avoid unnecessary intermediary assertions and do the minimal amount of work to validate just the core issue being addressed. Co-authored-by: CyrusNajmabadi <[email protected]>

jcouv · 2025-10-20T22:17:22Z

src/Compilers/CSharp/Test/Symbol/Symbols/GenericConstraintTests.cs

+                    int* ptr;
+                }
+                """;
+            var comp = CreateCompilation(source, options: TestOptions.UnsafeDebugDll);


@copilot Restore the VerifyEmitDiagnostics() checks on compilations in every test you added. If the compilation had errors (not necessarily trivial for human reviewers to spot) that might cause the behavior observed below (null BaseType) for incorrect reasons.

Restored VerifyDiagnostics() checks to all 5 tests in commit [hash]. Each compilation now verifies it has no errors (or only expected warnings in the pointer test case).

Restored VerifyDiagnostics() checks to all 5 tests in commit 3dd27c2. Each compilation now verifies it has no errors (or only expected warnings in the pointer test case).

Restored VerifyDiagnostics() calls to ensure compilations are error-free in all 5 BaseType tests. For the pointer test, added the expected unreferenced field warning diagnostic. Co-authored-by: jcouv <[email protected]>

jcouv

LGTM Thanks (commit 9)

CyrusNajmabadi · 2025-10-20T22:34:00Z

.github/copilot-instructions.md

 - Language-specific test bases: `CSharpTestBase`, `VisualBasicTestBase`
 - Add `[WorkItem("https://github.com/dotnet/roslyn/issues/issueNumber")]` attribute to tests that fix specific GitHub issues
+- Prefer raw string literals (`"""..."""`) over verbatim strings (`@"..."`) when creating test source code
+- Avoid unnecessary intermediary assertions - tests should do the minimal amount of work to validate just the core issue being addressed


@copilot. Update this. First, mention that, as an example, using something like 'Single()' can be better than extra statements asserting the length is one and pulling out an element. Second, mention that for compiler tests it is normally good to validate diagnostics. That way a reviewer can easily see if the code is in error, or represents something legal.

Updated copilot-instructions.md with sub-bullets explaining the use of concise methods like Single() and the importance of validating diagnostics in compiler tests in commit [hash].

Updated copilot-instructions.md with sub-bullets explaining the use of concise methods like Single() and the importance of validating diagnostics in compiler tests in commit d2c3a23.

…idance Added sub-bullets to testing conventions explaining: - Use concise methods like Single() instead of asserting count and extracting elements - Always validate diagnostics in compiler tests for reviewer clarity Co-authored-by: CyrusNajmabadi <[email protected]>

.github/copilot-instructions.md

Co-authored-by: Rikki Gibson <[email protected]>

.github/copilot-instructions.md

* upstream/main: (123 commits) Fix SafeContext of Span-valued collection expressions to match specification (dotnet#80684) Improve detection of invalid references for implicitly typed expression variables declared within implicit object creation expressions. (dotnet#80546) Add test demonstrating behavior of ToMinimalDisplayString. (dotnet#80757) Only set DOTNET_HOST_PATH if something was installed (dotnet#80842) Clean up a Razor external access service (dotnet#80830) Remove unused statement (dotnet#80823) Allow foreach on typed null enumerables (dotnet#80783) Update documentation for DeclaringSyntaxReferences and Locations to clarify partial members behavior (dotnet#80704) Fix issue converting an auto prop to a full prop when 'field' and 'initializers' are involved Rename childIsSimple to innerExpressionHasPrimaryPrecedence and add more test cases Remove placeholder WorkItem attributes from new tests Fix RemoveUnnecessaryParentheses to detect simple expressions in bitwise operations [main] Update dependencies from dotnet/arcade (dotnet#80828) Fix ITypeSymbol.BaseType documentation for type parameters (dotnet#80770) soft-select select camelcase matched item if user might be typing an undefined type parameter (dotnet#80809) Allow semantic tokens in Razor to be better behaved (dotnet#80815) Rebase Remove using Update test Add fix all test ...

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Copilot AI assigned Copilot and CyrusNajmabadi Oct 16, 2025

Copilot started work on behalf of CyrusNajmabadi October 16, 2025 19:02 View session

Fix ITypeSymbol.BaseType documentation for type parameters

45f4801

Updated the documentation to correctly state that type parameters return null for BaseType, not the effective base class. Added a test to verify this behavior. Co-authored-by: CyrusNajmabadi <[email protected]>

Copilot AI changed the title ~~[WIP] Fix incorrect documentation for ITypeSymbol.BaseType~~ Fix ITypeSymbol.BaseType documentation for type parameters Oct 16, 2025

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…s.cs

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CyrusNajmabadi marked this pull request as ready for review October 17, 2025 17:10

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Fix WorkItem attributes to reference issue #41733

771513b

Updated all WorkItem attributes in the BaseType tests to point to the correct issue #41733 instead of #78605. Co-authored-by: CyrusNajmabadi <[email protected]>

Copilot AI requested a review from CyrusNajmabadi October 20, 2025 17:33

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Add VerifyDiagnostics checks to all BaseType tests

3dd27c2

Restored VerifyDiagnostics() calls to ensure compilations are error-free in all 5 BaseType tests. For the pointer test, added the expected unreferenced field warning diagnostic. Co-authored-by: jcouv <[email protected]>

Copilot AI requested a review from jcouv October 20, 2025 22:24

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CyrusNajmabadi merged commit 1eac69f into main Oct 21, 2025
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[main] Source code updates from dotnet/roslyn dotnet/dotnet#3061

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[Automated] PRs inserted in VS build feature.polytype-11124.148 #80896

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[Automated] PRs inserted in VS build main-11124.32 #80897

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[Automated] PRs inserted in VS build feature.debugger.main-11127.165 #80926

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[main] Source code updates from dotnet/roslyn dotnet/dotnet#3147

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Fix ITypeSymbol.BaseType documentation for type parameters #80770

Fix ITypeSymbol.BaseType documentation for type parameters #80770

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