RemoveAllSyntaxTrees should preserve embedded syntax trees in Declaration Table.

Fixes #13925.

src/Compilers/VisualBasic/Portable/Compilation/VisualBasicCompilation.vb

@@ -424,6 +424,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
 
             Debug.Assert(syntaxTrees.All(Function(tree) syntaxTrees(syntaxTreeOrdinalMap(tree)) Is tree))
             Debug.Assert(syntaxTrees.SetEquals(rootNamespaces.Keys.AsImmutable(), EqualityComparer(Of SyntaxTree).Default))
+            Debug.Assert(embeddedTrees.All(Function(treeAndDeclaration) declarationTable.Contains(treeAndDeclaration.DeclarationEntry)))
 
             _options = options
             _syntaxTrees = syntaxTrees
@@ -971,7 +972,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             Return UpdateSyntaxTrees(ImmutableArray(Of SyntaxTree).Empty,
                                      ImmutableDictionary.Create(Of SyntaxTree, Integer)(),
                                      ImmutableDictionary.Create(Of SyntaxTree, DeclarationTableEntry)(),
-                                     DeclarationTable.Empty,
+                                     AddEmbeddedTrees(DeclarationTable.Empty, _embeddedTrees),
                                      referenceDirectivesChanged:=_declarationTable.ReferenceDirectives.Any())
         End Function
 

src/Compilers/VisualBasic/Portable/Declarations/DeclarationTable.vb

@@ -76,6 +76,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
             End If
         End Function
 
+        Public Function Contains(rootDeclaration As DeclarationTableEntry) As Boolean
+            Return rootDeclaration IsNot Nothing AndAlso
+                 (_allOlderRootDeclarations.Contains(rootDeclaration) OrElse _latestLazyRootDeclaration Is rootDeclaration)
+        End Function
+
         Public Function RemoveRootDeclaration(lazyRootDeclaration As DeclarationTableEntry) As DeclarationTable
             ' We can only reuse the cache if we're removing the decl that was just added.
             If _latestLazyRootDeclaration Is lazyRootDeclaration Then

src/Compilers/VisualBasic/Test/Semantic/Compilation/CompilationAPITests.vb

@@ -1961,5 +1961,52 @@ End Sub
 
             Assert.Throws(Of InvalidOperationException)(Function() CreateSubmission("?a + 1", previous:=s0))
         End Sub
+
+        <Fact>
+        <WorkItem(13925, "https://github.com/dotnet/roslyn/issues/13925")>
+        Public Sub RemoveAllSyntaxTreesAndEmbeddedTrees_01()
+            Dim compilation1 = CreateCompilationWithMscorlib(
+<compilation>
+    <file name="a.vb">
+Public Module C  
+    Sub Main()
+        System.Console.WriteLine(1)
+    End Sub
+End Module
+    </file>
+</compilation>, options:=TestOptions.ReleaseExe.WithEmbedVbCoreRuntime(True), references:={SystemRef})
+
+            compilation1.VerifyDiagnostics()
+
+            Dim compilation2 = compilation1.RemoveAllSyntaxTrees()
+            compilation2 = compilation2.AddSyntaxTrees(compilation1.SyntaxTrees)
+
+            compilation2.VerifyDiagnostics()
+            CompileAndVerify(compilation2, expectedOutput:="1")
+        End Sub
+
+        <Fact>
+        <WorkItem(13925, "https://github.com/dotnet/roslyn/issues/13925")>
+        Public Sub RemoveAllSyntaxTreesAndEmbeddedTrees_02()
+            Dim compilation1 = CreateCompilationWithMscorlibAndVBRuntime(
+<compilation>
+    <file name="a.vb">
+Public Module C  
+    Sub Main()
+        System.Console.WriteLine(1)
+    End Sub
+End Module
+    </file>
+</compilation>, options:=TestOptions.ReleaseExe.WithEmbedVbCoreRuntime(True))
+
+            compilation1.VerifyDiagnostics()
+
+            Dim compilation2 = compilation1.RemoveAllSyntaxTrees()
+            compilation2 = compilation2.AddSyntaxTrees(compilation1.SyntaxTrees)
+
+            compilation2.VerifyDiagnostics()
+            CompileAndVerify(compilation2, expectedOutput:="1")
+        End Sub
+
     End Class
 End Namespace