Allow char constants in C# interpolated strings

dotnet · Mar 20, 2024 · d7d542f · d7d542f
1 parent c0d7b49
commit d7d542f
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Showing 2 changed files with 29 additions and 3 deletions.
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_InterpolatedString.cs b/src/Compilers/CSharp/Portable/Binder/Binder_InterpolatedString.cs
@@ -141,14 +141,17 @@ private BoundExpression BindInterpolatedString(InterpolatedStringExpressionSynta
  if (!isResultConstant ||
  value.ConstantValueOpt == null ||
  !(interpolation is { FormatClause: null, AlignmentClause: null }) ||
- !(value.ConstantValueOpt is { IsString: true, IsBad: false }))
+ !(value.ConstantValueOpt is { IsBad: false } and ({ IsString: true } or { IsChar: true })))
  {
  isResultConstant = false;
  continue;
  }
+ ConstantValue valueConstantValueOpt = value.ConstantValueOpt.IsChar
+ ? ConstantValue.Create(value.ConstantValueOpt.CharValue.ToString())
+ : value.ConstantValueOpt;
  resultConstant = (resultConstant is null)
- ? value.ConstantValueOpt
- : FoldStringConcatenation(BinaryOperatorKind.StringConcatenation, resultConstant, value.ConstantValueOpt);
+ ? valueConstantValueOpt
+ : FoldStringConcatenation(BinaryOperatorKind.StringConcatenation, resultConstant, valueConstantValueOpt);
  continue;
  }
  case SyntaxKind.InterpolatedStringText:

diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/InterpolationTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/InterpolationTests.cs
@@ -18478,6 +18478,29 @@ .maxstack 1
  IL_0005: call ""void System.Console.Write(string)""
  IL_000a: ret
 }}
+");
+ }
+ [Theory]
+ [InlineData(@"$""{'c'}""", "c")]
+ [InlineData(@"$""{$""{'c'}h""}ar""", "char")]
+ public void CharConstantToConstString(string expression, string output)
+ {
+ var code = @"
+const string expression = " + expression + @";
+System.Console.Write(expression);";
+
+ var comp = CreateCompilation(new[] { code, GetInterpolatedStringHandlerDefinition(includeSpanOverloads: false, useDefaultParameters: false, useBoolReturns: false) });
+
+ var verifier = CompileAndVerify(comp, expectedOutput: output);
+
+ verifier.VerifyIL("<top-level-statements-entry-point>", @$"
+{{
+ // Code size 11 (0xb)
+ .maxstack 1
+ IL_0000: ldstr ""{output}""
+ IL_0005: call ""void System.Console.Write(string)""
+ IL_000a: ret
+}}
 ");
  }
  }