MA0185: Add tests and docs for literal-only interpolated strings

[Copilot]

MA0185 already detects string.Create(CultureInfo.InvariantCulture, $"literal") with no interpolations, but this wasn't explicitly documented or comprehensively tested.

Changes:

• Added test coverage for empty ($"") and multi-word literal strings
• Updated docs to explicitly list "no parameters at all" as a detected case
• Added example matching the issue scenario

Example:

// Already detected and reported by MA0185
var x = string.Create(CultureInfo.InvariantCulture, $"string without parameters.");

// Suggested fix
var x = $"string without parameters.";

All 11 MA0185 tests pass (2 new, 9 existing).

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• 1s1vsblobprodcus386.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/Meziantou.Analyzer.slnx --packages /home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true -l t tion.cs cal/bin/grep t lAnalyzer.cs ndor/bin/grep grep (dns block)
• pdfvsblobprodcus380.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/Meziantou.Analyzer.Test.csproj --packages /home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true -l t tion.cs tnet/tools/grep t s /usr/bin/grep grep (dns block)
• st8vsblobprodcus339.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/Meziantou.Analyzer.slnx --packages /home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true -l t tion.cs cal/bin/grep t lAnalyzer.cs ndor/bin/grep grep (dns block)
  • Triggering command: /usr/share/dotnet/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Meziantou.Analyzer/Meziantou.Analyzer/tests/Meziantou.Analyzer.Test/Meziantou.Analyzer.Test.csproj --packages /home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/Meziantou.Analyzer/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true -l t tion.cs tnet/tools/grep t s /usr/bin/grep grep (dns block)

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>Report diagnostic for passing a literal string without parameters as interpolated string argument</issue_title>
<issue_description>There's no analyzer rule (anywhere, that I know of) that reports a diagnostic when a string literal without parameters is passed as value for an argument that is an interpolated string handler.

var x = string.Create(CultureInfo.InvariantCulture, $"string without parameters."); // NOK
var x = string.Create(CultureInfo.InvariantCulture, $"Current time is {DateTime.Now:D}."); // OK
```</issue_description>

<agent_instructions>Can you update MA0185 to detect string.Create with string interpolation that doesn't contains any parts</agent_instructions>

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

<comments>
</comments>

• Fixes Report diagnostic for passing a literal string without parameters as interpolated string argument #982

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