Braces need escaping in raw string interpolation on net472

[jcouv]

The following test fails on net472 with System.FormatException : Input string was not in a correct format..
The problem is with the format string passed to string.Format, where the open brace (first character) isn't escaped: IL_000a: ldstr "{\r\n // Code size ....

        [Fact]
        public void TODO2()
        {
            int count = 31;
            string op = "shl";
            var value = $$"""
{
  // Code size        5 (0x5)
  .maxstack  2
  IL_0000:  ldarg.0
  IL_0001:  ldc.i4.s   {{count}}
  IL_0003:  {{op}}
  IL_0004:  ret
}
""";
        }

Message: 
System.FormatException : Input string was not in a correct format.

  Stack Trace: 
StringBuilder.AppendFormatHelper(IFormatProvider provider, String format, ParamsArray args)
String.FormatHelper(IFormatProvider provider, String format, ParamsArray args)
String.Format(String format, Object arg0, Object arg1)
NativeIntegerTests.TODO2() line 14939

.method public hidebysig 
	instance void TODO2 () cil managed 
{
	.custom instance void [xunit.core]Xunit.FactAttribute::.ctor() = (
		01 00 00 00
	)
	// Method begins at RVA 0x24f4fc
	// Code size 29 (0x1d)
	.maxstack 3
	.locals init (
		[0] int32 count,
		[1] string op,
		[2] string 'value'
	)

	// {
	IL_0000: nop
	// int num = 31;
	IL_0001: ldc.i4.s 31
	IL_0003: stloc.0
	// string arg = "shl";
	IL_0004: ldstr "shl"
	IL_0009: stloc.1
	// string text = string.Format("{\r\n  // Code size        5 (0x5)\r\n  .maxstack  2\r\n  IL_0000:  ldarg.0\r\n  IL_0001:  ldc.i4.s   {0}\r\n  IL_0003:  {1}\r\n  IL_0004:  ret\r\n}", num, arg);
	IL_000a: ldstr "{\r\n  // Code size        5 (0x5)\r\n  .maxstack  2\r\n  IL_0000:  ldarg.0\r\n  IL_0001:  ldc.i4.s   {0}\r\n  IL_0003:  {1}\r\n  IL_0004:  ret\r\n}"
	IL_000f: ldloc.0
	IL_0010: box [mscorlib]System.Int32
	IL_0015: ldloc.1
	IL_0016: call string [mscorlib]System.String::Format(string, object, object)
	IL_001b: stloc.2
	// }
	IL_001c: ret
} // end of method NativeIntegerTests::TODO2

Relates to test plan #55306

[CyrusNajmabadi]

Looking now.

[CyrusNajmabadi]

This may be a dupe of #59607. @jcouv do you repro this on latest builds?

[jcouv]

From offline investigation with @CyrusNajmabadi, we found the problem was using an old toolset compiler (Compiler version: '4.2.0-1.22108.11 (a29b6ae8)'). We couldn't repro with new bits (in unittest).
Closing