Disambiguate the names and trap labels of backing fields of extension properties

Author: smowton

java/kotlin-extractor/src/main/kotlin/KotlinFileExtractor.kt

@@ -759,7 +759,8 @@ open class KotlinFileExtractor(
         with("field", f) {
            DeclarationStackAdjuster(f).use {
                declarationStack.push(f)
-               return extractField(useField(f), f.name.asString(), f.type, parentId, tw.getLocation(f), f.visibility, f, isExternalDeclaration(f), f.isFinal)
+               val fNameSuffix = getExtensionReceiverType(f)?.let { it.classFqName?.asString()?.replace(".", "$$") } ?: ""
+               return extractField(useField(f), "${f.name.asString()}$fNameSuffix", f.type, parentId, tw.getLocation(f), f.visibility, f, isExternalDeclaration(f), f.isFinal)
            }
         }
     }

java/kotlin-extractor/src/main/kotlin/KotlinUsesExtractor.kt

@@ -1269,6 +1269,7 @@ open class KotlinUsesExtractor(
 
     fun useValueParameter(vp: IrValueParameter, parent: Label<out DbCallable>?): Label<out DbParam> =
         tw.getLabelFor(getValueParameterLabel(vp, parent))
+
     fun isDirectlyExposedCompanionObjectField(f: IrField) =
         f.hasAnnotation(FqName("kotlin.jvm.JvmField")) ||
         f.correspondingPropertySymbol?.owner?.let {
@@ -1283,9 +1284,20 @@ open class KotlinUsesExtractor(
                 null
         } ?: f.parent
 
+    // Gets a field's corresponding property's extension receiver type, if any
+    fun getExtensionReceiverType(f: IrField) =
+        f.correspondingPropertySymbol?.owner?.let {
+            (it.getter ?: it.setter)?.extensionReceiverParameter?.type
+        }
+
     fun getFieldLabel(f: IrField): String {
         val parentId = useDeclarationParent(getFieldParent(f), false)
-        return "@\"field;{$parentId};${f.name.asString()}\""
+        // Distinguish backing fields of properties based on their extension receiver type;
+        // otherwise two extension properties declared in the same enclosing context will get
+        // clashing trap labels. These are always private, so we can just make up a label without
+        // worrying about their names as seen from Java.
+        val extensionPropertyDiscriminator = getExtensionReceiverType(f)?.let { "extension;${useType(it)}" } ?: ""
+        return "@\"field;{$parentId};${extensionPropertyDiscriminator}${f.name.asString()}\""
     }
 
     fun useField(f: IrField): Label<out DbField> =

java/ql/test/kotlin/library-tests/clashing-extension-fields/test.expected

@@ -0,0 +1,9 @@
+|  |
+| <clinit> |
+| A |
+| B |
+| get |
+| getX |
+| invoke |
+| x$delegatepackagename$$subpackagename$$A |
+| x$delegatepackagename$$subpackagename$$B |

java/ql/test/kotlin/library-tests/clashing-extension-fields/test.kt

@@ -0,0 +1,7 @@
+package packagename.subpackagename
+
+public class A { }
+public class B { }
+
+val A.x : String by lazy { "HelloA" }
+val B.x : String by lazy { "HelloB" }

java/ql/test/kotlin/library-tests/clashing-extension-fields/test.ql

@@ -0,0 +1,5 @@
+import java
+
+from Class c
+where c.fromSource()
+select c.getAMember().toString()