Disable Obsolete checks for project level imports.

Fixes #4903.

src/Compilers/VisualBasic/Portable/Binding/ProjectImportsBinder.vb

@@ -33,6 +33,15 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         Public Overrides Function GetSyntaxReference(node As VisualBasicSyntaxNode) As SyntaxReference
             Return _tree.GetReference(node)
         End Function
+
+        Friend Overrides ReadOnly Property SuppressObsoleteDiagnostics As Boolean
+            Get
+                ' Obsolete diagnostics is not reported for project level imports. This is VS2013 behavior.
+                ' This also ensures that we don't get into circularity while binding imports because we are 
+                ' remapping diagnostics in SourceModuleSymbol.BindImports
+                Return True
+            End Get
+        End Property
     End Class
 
 End Namespace

src/Compilers/VisualBasic/Portable/Symbols/Source/SourceModuleSymbol.vb

@@ -369,6 +369,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                     binder.BindImportClause(globalImport.Clause, data, diagBagForThisImport)
 
                     ' Map diagnostics to new ones.
+                    ' Note, it is safe to resolve diagnostics here because we suppress obsolete diagnostics
+                    ' in ProjectImportsBinder.
                     For Each d As Diagnostic In diagBagForThisImport.AsEnumerable()
                         ' NOTE: Dev10 doesn't report 'ERR_DuplicateImport1' for project level imports. 
                         If d.Code <> ERRID.ERR_DuplicateImport1 Then

src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/SymbolErrorTests.vb

@@ -23618,5 +23618,60 @@ BC40012: event 'E2' implicitly declares 'remove_E2', which conflicts with a memb
             CompilationUtils.AssertTheseDeclarationDiagnostics(compilation1, expectedErrors1)
         End Sub
 
+        <Fact>
+        Public Sub NoObsoleteDiagnosticsForProjectLevelImports_01()
+            Dim options = TestOptions.ReleaseDll.WithGlobalImports(GlobalImport.Parse({"GlobEnumsClass"}))
+            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib(
+    <compilation>
+        <file name="a.vb"><![CDATA[
+<System.Serializable><System.Obsolete()> 
+Class GlobEnumsClass
+
+    Public Enum xEmailMsg
+        Option1
+        Option2
+    End Enum
+
+End Class
+
+Class Account
+    Property Status() As xEmailMsg
+End Class
+        ]]></file>
+    </compilation>, options)
+
+            CompileAndVerify(compilation).VerifyDiagnostics()
+        End Sub
+
+        <Fact>
+        Public Sub NoObsoleteDiagnosticsForProjectLevelImports_02()
+            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib(
+    <compilation>
+        <file name="a.vb"><![CDATA[
+Imports GlobEnumsClass
+
+<System.Serializable><System.Obsolete()> 
+Class GlobEnumsClass
+
+    Public Enum xEmailMsg
+        Option1
+        Option2
+    End Enum
+
+End Class
+
+Class Account
+    Property Status() As xEmailMsg
+End Class
+        ]]></file>
+    </compilation>, TestOptions.ReleaseDll)
+
+            compilation.AssertTheseDiagnostics(<expected>
+BC40008: 'GlobEnumsClass' is obsolete.
+Imports GlobEnumsClass
+        ~~~~~~~~~~~~~~
+                                               </expected>)
+        End Sub
+
     End Class
 End Namespace