Dynamic type for python

Author: oxisto

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

@@ -45,6 +45,10 @@ fun LanguageProvider.autoType(): Type {
     return AutoType(this.language)
 }
 
+fun LanguageProvider.dynamicType(): Type {
+    return DynamicType(this.language)
+}
+
 fun MetadataProvider?.incompleteType(): Type {
     return IncompleteType()
 }

cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/graph/types/AutoType.kt

@@ -30,10 +30,17 @@ import de.fraunhofer.aisec.cpg.graph.unknownType
 
 /**
  * This type represents a [Type] that uses auto-inference (usually from an initializer) to determine
- * it's actual type. It is commonly used in dynamically typed languages or in languages that have a
- * special keyword, such as `auto` in C++.
+ * its actual type. It is commonly used in languages that have a special keyword, such as `auto` in
+ * C++.
  *
- * Note: This is intentionally a distinct type and not the [UnknownType].
+ * Things to consider:
+ * 1) This is intentionally a distinct type and not the [UnknownType]. The type is known to the
+ *    compiler (or to us) at some point, e.g., after an assignment, but it is not specifically
+ *    specified in the source-code.
+ * 2) This should not be used to languages that have dynamic types. Once auto-type who was assigned
+ *    to [Expression.type] is "resolved", it should be replaced by the actual type that it
+ *    represents. Contrary to that, a [DynamicType] can change its internal type representation at
+ *    any point, e.g., after the next assignment.
  */
 class AutoType(override var language: Language<*>?) : Type("auto", language) {
     override fun reference(pointer: PointerType.PointerOrigin?): Type {

cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/graph/types/DynamicType.kt

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2024, Fraunhofer AISEC. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ *                    $$$$$$\  $$$$$$$\   $$$$$$\
+ *                   $$  __$$\ $$  __$$\ $$  __$$\
+ *                   $$ /  \__|$$ |  $$ |$$ /  \__|
+ *                   $$ |      $$$$$$$  |$$ |$$$$\
+ *                   $$ |      $$  ____/ $$ |\_$$ |
+ *                   $$ |  $$\ $$ |      $$ |  $$ |
+ *                   \$$$$$   |$$ |      \$$$$$   |
+ *                    \______/ \__|       \______/
+ *
+ */
+package de.fraunhofer.aisec.cpg.graph.types
+
+import de.fraunhofer.aisec.cpg.frontends.Language
+
+/**
+ * This type represents a [Type] that is dynamically determined at run-time. This is used for a
+ * [Language], which has dynamic runtime typing, such as Python or Java/TypeScript.
+ */
+class DynamicType(override var language: Language<*>?) : Type("dynamic", language) {
+    override fun reference(pointer: PointerType.PointerOrigin?): Type {
+        TODO("Not yet implemented")
+    }
+
+    override fun dereference(): Type {
+        TODO("Not yet implemented")
+    }
+}

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

@@ -528,13 +528,13 @@ open class SymbolResolver(ctx: TranslationContext) : ComponentPass(ctx) {
                 setOf(),
                 mapOf(),
                 setOf(),
-                CallResolutionResult.SuccessKind.UNRESOLVED,
+                UNRESOLVED,
                 source.scope,
             )
         val language = source.language
 
         if (language == null) {
-            result.success = CallResolutionResult.SuccessKind.PROBLEMATIC
+            result.success = PROBLEMATIC
             return result
         }
 
@@ -569,7 +569,7 @@ open class SymbolResolver(ctx: TranslationContext) : ComponentPass(ctx) {
 
         // If we have a "problematic" result, we can stop here. In this case we cannot really
         // determine anything more.
-        if (result.success == CallResolutionResult.SuccessKind.PROBLEMATIC) {
+        if (result.success == PROBLEMATIC) {
             result.bestViable = result.viableFunctions
             return result
         }

cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/PythonLanguage.kt

@@ -194,6 +194,20 @@ class PythonLanguage :
         return super.propagateTypeOfBinaryOperation(operation)
     }
 
+    override fun tryCast(
+        type: Type,
+        targetType: Type,
+        hint: HasType?,
+        targetHint: HasType?
+    ): CastResult {
+        // We model parameter declarations without type hints as a "dynamic"-type.
+        if (targetType is DynamicType && targetHint is ParameterDeclaration) {
+            return DirectMatch
+        }
+
+        return super.tryCast(type, targetType, hint, targetHint)
+    }
+
     companion object {
         /**
          * This is a "modifier" to differentiate parameters in functions that are "positional" only.

cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/PythonLanguageFrontend.kt

@@ -143,8 +143,8 @@ class PythonLanguageFrontend(language: Language<PythonLanguageFrontend>, ctx: Tr
     override fun typeOf(type: Python.AST.AST?): Type {
         return when (type) {
             null -> {
-                // No type information -> we return an autoType to infer things magically
-                autoType()
+                // No type information -> we return a dynamic type to infer things magically
+                dynamicType()
             }
             is Python.AST.Name -> {
                 this.typeOf(type.id)

cpg-language-python/src/test/kotlin/de/fraunhofer/aisec/cpg/frontends/python/PythonFrontendTest.kt

@@ -1589,6 +1589,23 @@ class PythonFrontendTest : BaseTest() {
         }
     }
 
+    @Test
+    fun testFunctionResolution() {
+        val topLevel = Path.of("src", "test", "resources", "python")
+        val tu =
+            analyzeAndGetFirstTU(listOf(topLevel.resolve("foobar.py").toFile()), topLevel, true) {
+                it.registerLanguage<PythonLanguage>()
+            }
+        assertNotNull(tu)
+
+        // ensure, we only have two functions and no inferred ones
+        val functions = tu.functions
+        assertEquals(2, functions.size)
+
+        val inferred = functions.filter { it.isInferred }
+        assertTrue(inferred.isEmpty())
+    }
+
     class PythonValueEvaluator : ValueEvaluator() {
         override fun computeBinaryOpEffect(
             lhsValue: Any?,

cpg-language-python/src/test/resources/python/foobar.py

@@ -0,0 +1,5 @@
+def foo(a):
+    return a+1
+
+def bar():
+    return foo(42)