Use ValueText to handle escaped identifiers and add tests.

src/Compilers/CSharp/Portable/Symbols/FunctionPointers/FunctionPointerMethodSymbol.cs

@@ -119,10 +119,10 @@ static CallingConvention getCallingConvention(FunctionPointerCallingConventionSy
                             case { CallingConventions: { Count: 1 } specifiers }:
                                 return specifiers[0].Name switch
                                 {
-                                    { Text: "Cdecl" } => CallingConvention.CDecl,
-                                    { Text: "Stdcall" } => CallingConvention.Standard,
-                                    { Text: "Thiscall" } => CallingConvention.ThisCall,
-                                    { Text: "Fastcall" } => CallingConvention.FastCall,
+                                    { ValueText: "Cdecl" } => CallingConvention.CDecl,
+                                    { ValueText: "Stdcall" } => CallingConvention.Standard,
+                                    { ValueText: "Thiscall" } => CallingConvention.ThisCall,
+                                    { ValueText: "Fastcall" } => CallingConvention.FastCall,
                                     // PROTOTYPE(func-ptr): Handle unrecognized specifiers
                                     var name => reportBadConventionAndReturn(name.Text, name, diagnostics)
                                 };

src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenFunctionPointersTests.cs

@@ -68,6 +68,10 @@ private CSharpCompilation CreateCompilationWithFunctionPointersAndIl(string sour
         [InlineData("unmanaged[Thiscall]", CallingConvention.ThisCall)]
         [InlineData("unmanaged[Stdcall]", CallingConvention.Standard)]
         [InlineData("unmanaged[Fastcall]", CallingConvention.FastCall)]
+        [InlineData("unmanaged[@Cdecl]", CallingConvention.CDecl)]
+        [InlineData("unmanaged[@Thiscall]", CallingConvention.ThisCall)]
+        [InlineData("unmanaged[@Stdcall]", CallingConvention.Standard)]
+        [InlineData("unmanaged[@Fastcall]", CallingConvention.FastCall)]
         // PROTOTYPE(func-ptr): Update SRM so it can decode the convention correctly
         //[InlineData("unmanaged", CallingConvention.Unmanaged)]
         internal void CallingConventions(string conventionString, CallingConvention expectedConvention)
@@ -116,11 +120,6 @@ public void M()
             );
         }
 
-        [Fact]
-        public void UnrecognizedCallingConventions()
-        {
-        }
-
         [Fact]
         public void RefParameters()
         {