avoid unnecessary O(n^2) work in localuse (#768)

Co-authored-by: WebFreak001 <gh@webfreak.org>

src/dcd/server/autocomplete/localuse.d

@@ -57,20 +57,21 @@ public AutocompleteResponse findLocalUse(AutocompleteRequest request,
 	config.fileName = "";
 	const(Token)[] tokenArray = getTokensForParser(cast(ubyte[]) request.sourceCode,
 			config, &cache);
+	auto sortedTokens = assumeSorted(tokenArray);
+	ScopeSymbolPair pair = generateAutocompleteTrees(tokenArray,
+		&rba, request.cursorPosition, moduleCache);
+	scope(exit) pair.destroy();
+
 	SymbolStuff getSymbolsAtCursor(size_t cursorPosition)
 	{
-		auto sortedTokens = assumeSorted(tokenArray);
 		auto beforeTokens = sortedTokens.lowerBound(cursorPosition);
-		ScopeSymbolPair pair = generateAutocompleteTrees(tokenArray,
-			&rba, request.cursorPosition, moduleCache);
 		auto expression = getExpression(beforeTokens);
 		return SymbolStuff(getSymbolsByTokenChain(pair.scope_, expression,
 			cursorPosition, CompletionType.location), pair.symbol, pair.scope_);
 	}
 
 	// gets the symbol matching to cursor pos
 	SymbolStuff stuff = getSymbolsAtCursor(cast(size_t)request.cursorPosition);
-	scope(exit) stuff.destroy();
 
 	// starts searching only if no ambiguity with the symbol
 	if (stuff.symbols.length == 1)
@@ -100,7 +101,6 @@ public AutocompleteResponse findLocalUse(AutocompleteRequest request,
 			{
 				size_t pos = cast(size_t) t.index + 1; // place cursor inside the token
 				SymbolStuff candidate = getSymbolsAtCursor(pos);
-				scope(exit) candidate.destroy();
 				if (candidate.symbols.length == 1 &&
 					candidate.symbols[0].location == sourceSymbol.location &&
 					candidate.symbols[0].symbolFile == sourceSymbol.symbolFile)