Comparing scope in case of a cache hit to avoid collisions

cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/ScopeManager.kt

@@ -76,10 +76,10 @@ class ScopeManager : ScopeProvider {
     data class Alias(var from: Name, var to: Name)
 
     /**
-     * A cache map of unique tags (computed with [Reference.buildUniqueTag]) and their respective
+     * A cache map of unique tags (computed with [Reference.uniqueTag]) and their respective
      * [ValueDeclaration]. This is used by [resolveReference] as a caching mechanism.
      */
-    private val symbolTable = mutableMapOf<ReferenceTag, ValueDeclaration>()
+    private val symbolTable = mutableMapOf<ReferenceTag, Pair<Reference, ValueDeclaration>>()
 
     /**
      * In some languages, we can define aliases for names. An example is renaming package imports in
@@ -625,16 +625,19 @@ class ScopeManager : ScopeProvider {
         // Retrieve a unique tag for the particular reference based on the current scope
         val tag = ref.uniqueTag
 
-        // If we find a match in our symbol table, we can immediately return the declaration
-        var decl = symbolTable[tag]
-        if (decl != null) {
-            return decl
+        // If we find a match in our symbol table, we can immediately return the declaration. We
+        // need to be careful about potential collisions in our tags, since they are based on the
+        // hash-code of the scope. We therefore take the extra precaution to compare the scope in
+        // case we get a hit. This should not take too much performance overhead.
+        val pair = symbolTable[tag]
+        if (pair != null && ref.scope == pair.first) {
+            return pair.second
         }
 
         val (scope, name) = extractScope(ref, startScope)
 
         // Try to resolve value declarations according to our criteria
-        decl =
+        val decl =
             resolve<ValueDeclaration>(scope) {
                     if (it.name.lastPartsMatch(name)) {
                         val helper = ref.resolutionHelper
@@ -666,7 +669,7 @@ class ScopeManager : ScopeProvider {
 
         // Update the symbol cache, if we found a declaration for the tag
         if (decl != null) {
-            symbolTable[tag] = decl
+            symbolTable[tag] = Pair(ref, decl)
         }
 
         return decl