Respond to PR feedback

src/Compilers/Core/Portable/FileSystem/FileUtilities.cs

@@ -361,5 +361,30 @@ internal static DateTime GetFileTimeStamp(string fullPath)
                 throw new IOException(e.Message);
             }
         }
+
+        internal static Stream OpenFileStream(string path)
+        {
+            try
+            {
+                return PortableShim.File.OpenRead(path);
+            }
+            catch (ArgumentException)
+            {
+                throw;
+            }
+            catch (IOException e)
+            {
+                if (e.GetType().Name == "DirectoryNotFoundException")
+                {
+                    throw new FileNotFoundException(e.Message, path, e);
+                }
+
+                throw;
+            }
+            catch (Exception e)
+            {
+                throw new IOException(e.Message, e);
+            }
+        }
     }
 }

src/Compilers/Core/Portable/MetadataReference/MetadataReference.cs

@@ -228,7 +228,7 @@ public MetadataReference WithProperties(MetadataReferenceProperties properties)
             MetadataReferenceProperties properties = default(MetadataReferenceProperties),
             DocumentationProvider documentation = null)
         {
-            var peStream = PortableShim.File.OpenRead(path);
+            var peStream = FileUtilities.OpenFileStream(path);
 
             // prefetch image, close stream to avoid locking it:
             var module = ModuleMetadata.CreateFromStream(peStream, PEStreamOptions.PrefetchEntireImage);
@@ -295,7 +295,7 @@ public static MetadataReference CreateFromAssembly(Assembly assembly)
             }
 
             string location = AssemblyLocationLightUp.GetAssemblyLocation(assembly);
-            Stream peStream = PortableShim.File.OpenRead(location);
+            Stream peStream = FileUtilities.OpenFileStream(location);
 
             // The file is locked by the CLR assembly loader, so we can create a lazily read metadata, 
             // which might also lock the file until the reference is GC'd.

src/Compilers/Core/Portable/MetadataReference/ModuleMetadata.cs

@@ -186,7 +186,7 @@ public static ModuleMetadata CreateFromStream(Stream peStream, PEStreamOptions o
         /// <exception cref="NotSupportedException">Reading from a file path is not supported by the platform.</exception>
         public static ModuleMetadata CreateFromFile(string path)
         {
-            return CreateFromStream(PortableShim.File.OpenRead(path));
+            return CreateFromStream(FileUtilities.OpenFileStream(path));
         }
 
         /// <summary>

src/Compilers/Core/Portable/PortableShim.cs

@@ -259,7 +259,7 @@ internal static class FileStream
             internal const string TypeName = "System.IO.FileStream";
 
             internal static readonly Type Type = ReflectionUtil.GetTypeFromEither(
-                contractName: $"${TypeName}, ${CoreNames.System_IO_FileSystem}",
+                contractName: $"{TypeName}, {CoreNames.System_IO_FileSystem}",
                 desktopName: TypeName);
 
             internal static readonly PropertyInfo Name = Type
@@ -347,7 +347,7 @@ internal static class Thread
             internal const string TypeName = "System.Threading.Thread";
 
             internal static readonly Type Type = ReflectionUtil.GetTypeFromEither(
-                contractName: $"${TypeName}, ${CoreNames.System_Threading_Thread}",
+                contractName: $"{TypeName}, {CoreNames.System_Threading_Thread}",
                 desktopName: TypeName);
 
             internal static readonly PropertyInfo CurrentThread = Type
@@ -364,7 +364,7 @@ internal static class RuntimeHelpers
             internal const string TypeName = "System.Runtime.CompilerServices.RuntimeHelpers";
 
             internal static readonly Type Type = ReflectionUtil.GetTypeFromEither(
-                contractName: $"${TypeName}, ${CoreNames.System_Runtime}",
+                contractName: $"{TypeName}, {CoreNames.System_Runtime}",
                 desktopName: TypeName);
 
             internal static readonly Action EnsureSufficientExecutionStack = Type
@@ -399,8 +399,8 @@ internal static class Extensions
                 internal const string TypeName = "System.Xml.XPath.Extensions";
 
                 internal static readonly Type Type = ReflectionUtil.GetTypeFromEither(
-                    contractName: $"${TypeName}, ${CoreNames.System_Runtime}",
-                    desktopName: $"${TypeName}, ${DesktopNames.System_Xml_Linq}");
+                    contractName: $"{TypeName}, {CoreNames.System_Runtime}",
+                    desktopName: $"{TypeName}, {DesktopNames.System_Xml_Linq}");
 
                 internal static readonly Func<XNode, string, IEnumerable<XElement>> XPathSelectElements = Type
                     .GetTypeInfo()