Remove unreachable code.

src/Workspaces/Core/Portable/FindSymbols/SymbolFinder_Declarations.cs

@@ -2,6 +2,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -85,6 +86,7 @@ private SearchQuery(Func<string, bool> predicate)
                 throw new ArgumentNullException(nameof(predicate));
             }
 
+            Kind = SearchKind.Custom;
             _predicate = predicate;
         }
 
@@ -152,6 +154,10 @@ public static partial class SymbolFinder
         internal static Task<IEnumerable<ISymbol>> FindDeclarationsAsync(
             Project project, SearchQuery query, SymbolFilter filter, CancellationToken cancellationToken)
         {
+            // All entrypoints to this function are Find functions that are only searching
+            // for specific strings (i.e. they never do a custom search).
+            Debug.Assert(query.Kind != SearchKind.Custom);
+
             if (project == null)
             {
                 throw new ArgumentNullException(nameof(project));
@@ -171,6 +177,10 @@ public static partial class SymbolFinder
         private static async Task<IEnumerable<ISymbol>> FindDeclarationsAsyncImpl(
             Project project, SearchQuery query, SymbolFilter criteria, CancellationToken cancellationToken)
         {
+            // All entrypoints to this function are Find functions that are only searching
+            // for specific strings (i.e. they never do a custom search).
+            Debug.Assert(query.Kind != SearchKind.Custom);
+
             var compilation = await project.GetCompilationAsync(cancellationToken).ConfigureAwait(false);
 
             var list = new List<ISymbol>();
@@ -267,6 +277,10 @@ private static IEnumerable<ISymbol> TranslateNamespaces(List<ISymbol> symbols, C
             Solution solution, IAssemblySymbol assembly, PortableExecutableReference referenceOpt, 
             SearchQuery query, SymbolFilter filter, List<ISymbol> list, CancellationToken cancellationToken)
         {
+            // All entrypoints to this function are Find functions that are only searching
+            // for specific strings (i.e. they never do a custom search).
+            Debug.Assert(query.Kind != SearchKind.Custom);
+
             using (Logger.LogBlock(FunctionId.SymbolFinder_Assembly_AddDeclarationsAsync, cancellationToken))
             {
                 if (referenceOpt != null)

src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo.cs

@@ -82,12 +82,20 @@ internal partial class SymbolTreeInfo
         public Task<IEnumerable<ISymbol>> FindAsync(
             SearchQuery query, IAssemblySymbol assembly, SymbolFilter filter, CancellationToken cancellationToken)
         {
+            // All entrypoints to this function are Find functions that are only searching
+            // for specific strings (i.e. they never do a custom search).
+            Debug.Assert(query.Kind != SearchKind.Custom);
+
             return this.FindAsync(query, new AsyncLazy<IAssemblySymbol>(assembly), filter, cancellationToken);
         }
 
         public async Task<IEnumerable<ISymbol>> FindAsync(
             SearchQuery query, AsyncLazy<IAssemblySymbol> lazyAssembly, SymbolFilter filter, CancellationToken cancellationToken)
         {
+            // All entrypoints to this function are Find functions that are only searching
+            // for specific strings (i.e. they never do a custom search).
+            Debug.Assert(query.Kind != SearchKind.Custom);
+
             return SymbolFinder.FilterByCriteria(
                 await FindAsyncWorker(query, lazyAssembly, cancellationToken).ConfigureAwait(false),
                 filter);
@@ -95,6 +103,10 @@ internal partial class SymbolTreeInfo
 
         private Task<IEnumerable<ISymbol>> FindAsyncWorker(SearchQuery query, AsyncLazy<IAssemblySymbol> lazyAssembly, CancellationToken cancellationToken)
         {
+            // All entrypoints to this function are Find functions that are only searching
+            // for specific strings (i.e. they never do a custom search).
+            Debug.Assert(query.Kind != SearchKind.Custom);
+
             // If the query has a specific string provided, then call into the SymbolTreeInfo
             // helpers optimized for lookup based on an exact name.
             switch (query.Kind)
@@ -105,9 +117,6 @@ private Task<IEnumerable<ISymbol>> FindAsyncWorker(SearchQuery query, AsyncLazy<
                     return this.FindAsync(lazyAssembly, query.Name, ignoreCase: true, cancellationToken: cancellationToken);
                 case SearchKind.Fuzzy:
                     return this.FuzzyFindAsync(lazyAssembly, query.Name, cancellationToken);
-                case SearchKind.Custom:
-                    // Otherwise, we'll have to do a slow linear search over all possible symbols.
-                    return this.FindAsync(lazyAssembly, query.GetPredicate(), cancellationToken);
             }
 
             throw new InvalidOperationException();
@@ -162,28 +171,6 @@ private Task<IEnumerable<ISymbol>> FindAsyncWorker(SearchQuery query, AsyncLazy<
             return result;
         }
 
-        /// <summary>
-        /// Slow, linear scan of all the symbols in this assembly to look for matches.
-        /// </summary>
-        private async Task<IEnumerable<ISymbol>> FindAsync(AsyncLazy<IAssemblySymbol> lazyAssembly, Func<string, bool> predicate, CancellationToken cancellationToken)
-        {
-            var result = new List<ISymbol>();
-            IAssemblySymbol assembly = null;
-            for (int i = 0, n = _nodes.Length; i < n; i++)
-            {
-                cancellationToken.ThrowIfCancellationRequested();
-                var node = _nodes[i];
-                if (predicate(node.Name))
-                {
-                    assembly = assembly ?? await lazyAssembly.GetValueAsync(cancellationToken).ConfigureAwait(false);
-
-                    result.AddRange(Bind(i, assembly.GlobalNamespace, cancellationToken));
-                }
-            }
-
-            return result;
-        }
-
         private static StringComparer GetComparer(bool ignoreCase)
         {
             return ignoreCase ? CaseInsensitiveComparison.Comparer : StringComparer.Ordinal;