Use CompareExchange

jcouv · jcouv · commit 27d7a4b2baba · 2022-01-14T12:25:03.000-08:00
diff --git a/src/Compilers/CSharp/Portable/Symbols/Tuples/TupleTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Tuples/TupleTypeSymbol.cs
@@ -1051,7 +1051,11 @@ internal SmallDictionary<Symbol, Symbol> UnderlyingDefinitionToMemberMap
             {
                 get
                 {
-                    return _lazyUnderlyingDefinitionToMemberMap ??= computeDefinitionToMemberMap();
+                    if (_lazyUnderlyingDefinitionToMemberMap is null)
+                    {
+                        Interlocked.CompareExchange(ref _lazyUnderlyingDefinitionToMemberMap, computeDefinitionToMemberMap(), null);
+                    }
+                    return _lazyUnderlyingDefinitionToMemberMap;
 
                     SmallDictionary<Symbol, Symbol> computeDefinitionToMemberMap()
                     {

Original file line number	Diff line number	Diff line change
`@@ -1051,7 +1051,11 @@ internal SmallDictionary<Symbol, Symbol> UnderlyingDefinitionToMemberMap`
`1051`	`1051`	`{`
`1052`	`1052`	`get`
`1053`	`1053`	`{`
`1054`		`- return _lazyUnderlyingDefinitionToMemberMap ??= computeDefinitionToMemberMap();`
	`1054`	`+ if (_lazyUnderlyingDefinitionToMemberMap is null)`
	`1055`	`+ {`
	`1056`	`+ Interlocked.CompareExchange(ref _lazyUnderlyingDefinitionToMemberMap, computeDefinitionToMemberMap(), null);`
	`1057`	`+ }`
	`1058`	`+ return _lazyUnderlyingDefinitionToMemberMap;`
`1055`	`1059`
`1056`	`1060`	`SmallDictionary<Symbol, Symbol> computeDefinitionToMemberMap()`
`1057`	`1061`	`{`