Avoid problems with string to ReadOnlySpan<T>

dotnet · Jul 15, 2024 · 5b0ace4 · 5b0ace4
1 parent c9f6e1b
commit 5b0ace4
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Showing 3 changed files with 18 additions and 4 deletions.
diff --git a/src/Compilers/CSharp/Test/Emit3/FirstClassSpanTests.cs b/src/Compilers/CSharp/Test/Emit3/FirstClassSpanTests.cs
@@ -1981,7 +1981,9 @@ public static void R(Expression<Action> e) { }
                 public static void M({{type}}<string> x) { }
             }
             """;
-        var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.Regular.WithLanguageVersion(langVersion));
+        var comp = CreateCompilationWithSpanAndMemoryExtensions(source,
+            parseOptions: TestOptions.Regular.WithLanguageVersion(langVersion),
+            noStringToReadOnlySpanConversionInSource: true);
         var verifier = CompileAndVerify(comp).VerifyDiagnostics();
         verifier.VerifyIL("<top-level-statements-entry-point>", $$"""
             {

diff --git a/src/Compilers/Test/Utilities/CSharp/CSharpTestBase.cs b/src/Compilers/Test/Utilities/CSharp/CSharpTestBase.cs
@@ -2575,15 +2575,16 @@ protected static CSharpCompilation CreateCompilationWithIndexAndRangeAndSpan(CSh
                 parseOptions: parseOptions);
         }
 
-        protected static CSharpCompilation CreateCompilationWithSpanAndMemoryExtensions(CSharpTestSource text, CSharpCompilationOptions options = null, CSharpParseOptions parseOptions = null, TargetFramework targetFramework = TargetFramework.NetCoreApp)
+        protected static CSharpCompilation CreateCompilationWithSpanAndMemoryExtensions(CSharpTestSource text, CSharpCompilationOptions options = null, CSharpParseOptions parseOptions = null, TargetFramework targetFramework = TargetFramework.NetCoreApp, bool noStringToReadOnlySpanConversionInSource = false)
         {
             if (ExecutionConditionUtil.IsCoreClr)
             {
                 return CreateCompilation(text, targetFramework: targetFramework, options: options, parseOptions: parseOptions);
             }
             else
             {
-                var reference = CreateCompilation(new[] { TestSources.Span, TestSources.MemoryExtensions }, options: TestOptions.UnsafeReleaseDll).VerifyDiagnostics();
+                var spanSource = noStringToReadOnlySpanConversionInSource ? TestSources.SpanWithoutStringConversion : TestSources.Span;
+                var reference = CreateCompilation(new[] { spanSource, TestSources.MemoryExtensions }, options: TestOptions.UnsafeReleaseDll).VerifyDiagnostics();
 
                 return CreateCompilation(
                     text,

diff --git a/src/Compilers/Test/Utilities/CSharp/TestSources.cs b/src/Compilers/Test/Utilities/CSharp/TestSources.cs
@@ -8,6 +8,11 @@ namespace Microsoft.CodeAnalysis.CSharp.Test.Utilities
 {
     internal static class TestSources
     {
+        private const string StringToReadOnlySpanConversion = """
+            // NOTE: This is defined on String in the BCL (and the target type is non-generic ReadOnlySpan<char>).
+            public static implicit operator ReadOnlySpan<T>(string stringValue) => string.IsNullOrEmpty(stringValue) ? default : new ReadOnlySpan<T>((T[])(object)stringValue.ToCharArray());
+            """;
+
         internal const string Span = @"
 namespace System
 {
@@ -164,7 +169,7 @@ public ref readonly T Current
 
         public static implicit operator ReadOnlySpan<T>(T[] array) => array == null ? default : new ReadOnlySpan<T>(array);
 
-        public static implicit operator ReadOnlySpan<T>(string stringValue) => string.IsNullOrEmpty(stringValue) ? default : new ReadOnlySpan<T>((T[])(object)stringValue.ToCharArray());
+        " + StringToReadOnlySpanConversion + @"
 
         public ReadOnlySpan<T> Slice(int offset, int length) => new ReadOnlySpan<T>(this.arr, offset, length);
     }
@@ -239,6 +244,12 @@ public static T[] ToArray<T>(void* ptr, int count)
     }
 }";
 
+        /// <summary>
+        /// Use if the non-standardly defined string-to-ReadOnlySpan conversion causes problems
+        /// (e.g., when converting from null to ReadOnlySpan you would get an ambiguity for the user-defined conversion).
+        /// </summary>
+        internal static readonly string SpanWithoutStringConversion = Span.Replace(StringToReadOnlySpanConversion, "");
+
         internal const string Index = @"
 
 namespace System