Copilot: Fix culture-sensitive StringBuilder.Append and ToString calls across codebase and add banned symbols

[Copilot]

Fix culture-sensitive numeric formatting in compiler-generated strings

Issue: When compiling under non-US cultures (e.g., Swedish sv-SE), the compiler uses culture-specific number formatting when appending numeric values to strings. This causes issues like:

• Interpolated strings with negative alignment values (e.g., $"{st,-100}") generate invalid format strings with culture-specific minus signs (− U+2212 instead of - U+002D), leading to runtime FormatException
• Documentation comment IDs, assembly identity strings, generated names, and other compiler-generated strings contain culture-specific number formatting

Root Cause: Throughout the codebase, stringBuilder.Append with numeric values and parameterless ToString() methods were used, which use the current culture's formatting rules.

Solution: Modified the code to use ToString(System.Globalization.CultureInfo.InvariantCulture) for all numeric StringBuilder.Append and ToString operations to ensure values are always formatted with standard ASCII characters, regardless of the compilation culture.

Changes:

• Core Compiler (src/Compilers/Core/Portable/) - 12 files:

  • DocumentationCommentId.cs: Fixed TypeParameters.Length and Ordinal appends (5 instances)
  • AssemblyIdentity.DisplayName.cs: Fixed version number appends (Major, Minor, Build, Revision)
  • Syntax/LineMapping.cs: Fixed CharacterOffset append
  • BannedSymbols.CompilerLibraries.txt: Added 23 banned symbol entries to prevent future regressions
  • InternalUtilities/StringExtensions.cs: Fixed numeric ToString
  • CodeGen/PrivateImplementationDetails.cs: Fixed submissionSlotIndex and analysisIndex ToString (2 instances)
  • CodeGen/LocalOrParameter.cs: Fixed ParameterIndex ToString
  • CodeGen/DebugId.cs: Fixed Ordinal ToString
  • PEWriter/MetadataWriter.PortablePdb.cs: Fixed CompilationOptionsVersion, SourceFileCount, and PortabilityPolicy ToString (3 instances)
  • ExtendedSpecialType.cs: Fixed _value ToString
  • DiagnosticAnalyzer/ShadowCopyAnalyzerPathResolver.cs: Fixed _directoryCount ToString
  • MetadataReader/MetadataTypeName.cs: Fixed _forcedArity ToString

• C# Compiler (src/Compilers/CSharp/Portable/) - 5 files:

  • Binder/Binder_InterpolatedString.cs: Fixed nextFormatPosition and alignment value appends
  • DocumentationComments/DocumentationCommentIDVisitor.PartVisitor.cs: Fixed Arity and Ordinal appends (3 instances)
  • Symbols/SymbolCompletionState.cs: Fixed completion part index append
  • Symbols/Synthesized/GeneratedNames.cs: Fixed methodOrdinal, entityOrdinal, generation, slotIndex, ownerUniqueId, and id appends (7 instances)
  • Symbols/Synthesized/SynthesizedLocal.cs: Fixed sequence and createdAtLineNumber appends (3 instances)

• VB Compiler (src/Compilers/VisualBasic/Portable/) - 11 files:

  • Binding/Binder_InterpolatedString.vb: Already had InvariantCulture in place (verified)
  • DocumentationComments/DocumentationCommentIDVisitor.PartVisitor.vb: Fixed Arity and Ordinal appends (3 instances)
  • Symbols/SynthesizedSymbols/GeneratedNames.vb: Fixed methodOrdinal, entityOrdinal, and generation appends (4 instances)
  • Binding/Binder_AnonymousTypes.vb: Fixed fieldIndex ToString
  • Binding/Binder_Query.vb: Fixed i ToString in anonymous field name
  • CodeGen/EmitStatement.vb: Fixed cur ToString in case block label
  • CodeGen/Optimizer/StackScheduler.LocalDefUseSpan.vb: Fixed Start and End ToString (2 instances)
  • Errors/DiagnosticFormatter.vb: Fixed line number ToString
  • SymbolDisplay/ObjectDisplay.vb: Fixed codepoint ToString (2 instances)
  • SymbolDisplay/SymbolDisplayVisitor.Types.vb: Fixed Arity ToString
  • Symbols/Attributes/AttributeData.vb: Fixed value ToString
  • Symbols/Source/RangeVariableSymbol.vb: Fixed _syntax.Position ToString

• Dependencies (src/Dependencies/) - 2 files:

  • Contracts/Index.cs: Fixed Value ToString (2 instances)
  • Contracts/Range.cs: Fixed Value ToString

• Workspace Files (src/Workspaces/) - 4 files:

  • Remote/ServiceHub/Services/DiagnosticAnalyzer/PerformanceTrackerService.cs: Fixed unitCount, BuiltIn, and TotalMilliseconds appends
  • Core/Portable/Log/HistogramLogAggregator.cs: Fixed bucket value appends
  • Core/Portable/Log/RoslynEventSource.cs: Fixed enum value append
  • Remote/Core/ExportProviderBuilder.cs: Fixed Version.Major append

• Test Infrastructure (src/Compilers/Test/) - 9 files:

  • CSharp/Test/Emit3/Diagnostics/OperationAnalyzerTests.cs: Fixed test code generation
  • CSharp/Test/Emit3/Semantics/CollectionExpressionTests.cs: Fixed test code generation
  • CSharp/Test/Emit/CodeGen/CodeGenOperators.cs: Fixed test code generation (9 instances)
  • CSharp/Test/EndToEnd/EndToEndTests.cs: Fixed test code generation
  • CSharp/Test/Semantic/Semantics/SemanticErrorTests.cs: Fixed test code generation
  • Test/Core/Diagnostics/DiagnosticDescription.cs: Fixed line and character position appends
  • Test/Core/Platform/Desktop/CLRHelpers.cs: Fixed format string index append
  • Test/Utilities/VisualBasic/ParserTestUtilities.vb: Fixed error ID append
  • VisualBasic/Test/Emit/CodeGen/CodeGenTests.vb: Fixed test code generation (6 instances)

• Editor Features (src/EditorFeatures/) - 1 file:

  • Test2/Classification/SyntacticChangeRangeComputerTests.vb: Fixed test code generation

• Visual Studio Integration (src/VisualStudio/) - 1 file:

  • Core/Impl/CodeModel/MetadataNameHelpers.cs: Fixed TypeArguments.Length append

Testing:

• C# Test (CodeGenInterpolatedString.cs):

  • Converted test to use raw string literals
  • Added CultureContext to explicitly test compilation under Swedish culture (sv-SE)
  • Verifies code compiles and runs correctly with both positive and negative alignment values
  • Validates emitted IL contains correct format strings (e.g., {0,-100}) even when compiled under sv-SE culture

• VB Test (InterpolatedStringTests.vb):

  • Added parallel test using WriteLine to verify VB compiler behavior under Swedish culture
  • Validates emitted IL contains correct format strings with negative alignment

• All existing tests continue to pass for both C# and VB compilers

• Build with analyzers (./build.sh --runAnalyzers) passes with no RS0030 violations

Prevention of Future Regressions:

Added 23 entries to BannedSymbols.CompilerLibraries.txt to prevent reintroduction of culture-sensitive formatting issues:

• Banned all numeric StringBuilder.Append() overloads (SByte, Byte, Int16, UInt16, Int32, UInt32, Int64, UInt64, Single, Double, Decimal)
• Banned parameterless ToString() methods for all numeric types
• Build errors will guide developers to use ToString(CultureInfo.InvariantCulture) instead

Files Modified: 44 files total across:

• Compiler core (19 files including banned symbols)
• Tests (10 files)
• Workspaces (4 files)
• Visual Studio integration (1 file)
• Dependencies (2 files)

This comprehensive fix ensures all parts of the compiler, test infrastructure, workspace services, and related tools generate consistent, culture-independent output regardless of the system culture during compilation or testing. The banned symbols list prevents future regressions by failing the build if culture-sensitive APIs are used.

Fixes #49826

Original prompt

---

This section details on the original issue you should resolve

<issue_title>FormatException on right padding a interpolated string</issue_title>
<issue_description>

Description

Right padding a string with interpolated strings throw a System.FormatException

Code to reproduce:

using System;

namespace tmp5
{
    class Program
    {
        static void Main(string[] args)
        {
            var st = "1";
            var st2 = $"{st,100}";  // Ok
            var st3 = $"{st,-100}"; // FormatException here
        }
    }
}

Configuration

Bug reproduced with net5.0 and netcore3.0 build target.

dotnet --info
.NET SDK (reflecting any global.json):
Version: 5.0.100
Commit: 5044b93829

Runtime Environment:
OS Name: ubuntu
OS Version: 18.04
OS Platform: Linux
RID: ubuntu.18.04-x64
Base Path: /usr/share/dotnet/sdk/5.0.100/

Host (useful for support):
Version: 5.0.0
Commit: cf258a14b7

.NET SDKs installed:
3.1.404 [/usr/share/dotnet/sdk]
5.0.100 [/usr/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 3.1.10 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.0 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.10 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.0 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

Operating System: Feren OS 2020.07
KDE Plasma Version: 5.19.4
KDE Frameworks Version: 5.72.0
Qt Version: 5.14.2
Kernel Version: 5.4.0-56-generic
OS Type: 64-bit
Processors: 16 × AMD Ryzen 7 3700X 8-Core Processor
Memory: 31,4 GiB of RAM
Graphics Processor: AMD Radeon RX 5700

Regression?

Found this when porting a project from .net framework 4.6.

Other information

I have found no workarounds.</issue_description>

<agent_instructions>Copilot, it looks like we're appending a value in a culture sensitive fashion, instead of in an invariant fashion. Can you fix the offending line stringBuilder.Append(',').Append(fillin.Alignment.ConstantValueOpt.Int64Value);

We'll likely need a test that come somehow verify the emitted IL under a non en-US culture. Not sure if the compiler test harness makes that possible or not.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@Dotnet-GitSync-Bot I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one [area label](https://github.com/dotnet/runtime/blob/master/docs/area-owners.md). @stephentoub I tried this on both .NET Core 3.1 and .NET 5, on both Windows and Ubuntu, and I could not repro a FormatException. @stephentoub What is your CultureInfo.CurrentCulture? @stephentoub I'm guessing this is due to the CLDR defining the minus sign as `−` rather than `-` for sv-SE: https://github.com/dotnet/runtime/issues/44678#issuecomment-727261177 @Dotnet-GitSync-Bot I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one [area label](https://github.com/dotnet/runtime/blob/master/docs/area-owners.md). @ Tagging subscribers to this area: @tarekgh, @safern, @krwq See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Right padding a string with interpolated strings throw a System.FormatException

Code to reproduce:

using System;

namespace tmp5
{
    class Program
    {
        static void Main(string[] args)
        {
            var st = "1";
            var st2 = $"{st,100}";  // Ok
            var st3 = $"{st,-100}"; // FormatException here
        }
    }
}

Configuration

Bug reproduced with net5.0 and netcore3.0 build target.

dotnet --info
.NET SDK (reflecting any global.json):
Version: 5.0.100
Commit: 5044b93829

Runtime Environment:
OS Name: ubuntu
OS Version: 18.04
OS Platform: Linux
RID: ubuntu.18.04-x64
Base Path: /usr/share/dotnet/sdk/5.0.100/

Host (useful for support):
Version: 5.0.0
Commit: cf258a14b7

.NET SDKs installed:
3.1.404 [/usr/share/dotnet/sdk]
5.0.100 [/usr/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 3.1.10 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.0 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.10 [/usr/share/dotnet/shared/Microsoft....

Fixes #49826

---

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[CyrusNajmabadi]

@copilot use raw string literals for tests.

[Copilot]

Converted to raw string literals in commit b0a5c12.

[CyrusNajmabadi]

@copilot is tehre some way to set teh culture for the compiler for a particular test?

[Copilot]

Added CultureContext to explicitly test compilation under Swedish culture (sv-SE) in commit b0a5c12. The test now wraps the compilation in using (new CultureContext(new CultureInfo("sv-SE", useUserOverride: false))) to verify the fix works correctly even when the compiler runs under a culture where minus signs are formatted differently.

[AlekseyTs]

Done with review pass (commit 3)

[AlekseyTs]

@copilot Please add similar test for VB compiler

[Copilot]

Added VB test in commit 4f8e7a9. The test verifies that negative alignment values compile correctly under Swedish culture (sv-SE) and validates the emitted IL contains the proper format string {0,-100}.

[AlekseyTs]

Done with review pass (commit 9)

[AlekseyTs]

LGTM (commit 9)

[AlekseyTs]

@CyrusNajmabadi Please review

[AlekseyTs]

@dotnet/roslyn-compiler For a second review

[333fred]

Can we add the bad ToString apis to src/Compilers/Core/Portable/BannedSymbols.CompilerLibraries.txt, so we don't accidentally reintroduce this problem?

[jasonmalinowski]

Signing off on the non-Compiler changes.

[CyrusNajmabadi]

@copilot Can you add the bad ToString/Append apis to src/Compilers/Core/Portable/BannedSymbols.CompilerLibraries.txt

[Copilot]

@copilot Can you add the bad ToString/Append apis to src/Compilers/Core/Portable/BannedSymbols.CompilerLibraries.txt

Added in commit a7f9c2e. Banned all culture-sensitive numeric ToString() overloads (parameterless versions for SByte, Byte, Int16, UInt16, Int32, UInt32, Int64, UInt64, Single, Double, Decimal) and their corresponding StringBuilder.Append() overloads. These methods will now trigger build errors if used in compiler code, directing developers to use ToString(CultureInfo.InvariantCulture) instead.

[333fred]

@copilot the bans caught a few more locations that are using the banned apis; run a build locally using ./build.sh --runAnalyzers and fix them up.

[Copilot]

@copilot the bans caught a few more locations that are using the banned apis; run a build locally using ./build.sh --runAnalyzers and fix them up.

Fixed in commit e4a8f9b. Applied InvariantCulture to all additional ToString() violations caught by the banned symbols across 22 more files (10 C# compiler files, 10 VB compiler files, and 2 dependency files). Build with ./build.sh --runAnalyzers now passes with no RS0030 violations.