From 1730f8bde2f2189da2f080a3c3dfddd2060fe666 Mon Sep 17 00:00:00 2001
From: Christian Banse <oxisto@aybaze.com>
Date: Fri, 3 Mar 2023 09:21:39 +0100
Subject: [PATCH] added missing pass

---
 .../aisec/cpg/passes/GoTypeCastingPass.kt     | 131 ++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 cpg-language-go/src/main/kotlin/de/fraunhofer/aisec/cpg/passes/GoTypeCastingPass.kt

diff --git a/cpg-language-go/src/main/kotlin/de/fraunhofer/aisec/cpg/passes/GoTypeCastingPass.kt b/cpg-language-go/src/main/kotlin/de/fraunhofer/aisec/cpg/passes/GoTypeCastingPass.kt
new file mode 100644
index 0000000000..ea3f09f4c2
--- /dev/null
+++ b/cpg-language-go/src/main/kotlin/de/fraunhofer/aisec/cpg/passes/GoTypeCastingPass.kt
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2023, 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.passes
+
+import de.fraunhofer.aisec.cpg.TranslationResult
+import de.fraunhofer.aisec.cpg.frontends.Language
+import de.fraunhofer.aisec.cpg.frontends.LanguageFrontend
+import de.fraunhofer.aisec.cpg.frontends.golang.GoLanguage
+import de.fraunhofer.aisec.cpg.graph.*
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.CallExpression
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.CastExpression
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.DeclaredReferenceExpression
+import de.fraunhofer.aisec.cpg.graph.types.TypeParser
+import de.fraunhofer.aisec.cpg.helpers.SubgraphWalker
+import de.fraunhofer.aisec.cpg.passes.order.ExecuteBefore
+
+/**
+ * In Go, it is possible to convert compatible types by "calling" the type name as a function, such
+ * as
+ *
+ * ```go
+ * var i = int(2.0)
+ * ```
+ *
+ * This is also possible with more complex types, such as interfaces or aliased types, as long as
+ * they are compatible. Because types in the same package can be defined in multiple files, we
+ * cannot decide during the frontend run. Therefore, we need to execute this pass before the
+ * [CallResolver] and convert certain [CallExpression] nodes into a [CastExpression].
+ */
+@ExecuteBefore(CallResolver::class)
+@ExecuteBefore(DFGPass::class)
+class GoTypeCastingPass : Pass() {
+    override fun accept(t: TranslationResult) {
+        scopeManager = t.scopeManager
+
+        var walker = SubgraphWalker.ScopedWalker(scopeManager)
+        walker.registerHandler { _, parent, node ->
+            // We are only interested in CallExpressions
+            if (node is CallExpression) {
+                handleCall(node, parent)
+            }
+        }
+
+        for (tu in t.translationUnits) {
+            walker.iterate(tu)
+        }
+    }
+
+    private fun handleCall(call: CallExpression, parent: Node?) {
+        // We need to check, whether the "callee" refers to a type and if yes, convert it into a
+        // cast expression. And this is only really necessary, if the function call has a single
+        // argument.
+        val callee = call.callee
+        if (parent != null && callee is DeclaredReferenceExpression && call.arguments.size == 1) {
+            val language = parent.language ?: GoLanguage()
+
+            // First, check if this is a built-in type
+            if (language.primitiveTypes.contains(callee.name.toString())) {
+                replaceCallWithCast(callee.name.toString(), language, parent, call)
+            } else {
+                // If not, then this could still refer to an existing type. We need to make sure
+                // that we take the current namespace into account
+                val fqn =
+                    if (callee.name.parent == null) {
+                        scopeManager.currentNamespace.fqn(callee.name.localName)
+                    } else {
+                        callee.name
+                    }
+
+                if (TypeManager.getInstance().typeExists(fqn.toString())) {
+                    replaceCallWithCast(fqn, language, parent, call)
+                }
+            }
+        }
+    }
+
+    private fun replaceCallWithCast(
+        typeName: CharSequence,
+        language: Language<out LanguageFrontend>,
+        parent: Node,
+        call: CallExpression,
+    ) {
+        val cast = parent.newCastExpression(call.code)
+        cast.location = call.location
+        cast.castType = TypeParser.createFrom(typeName, false, language)
+        cast.expression = call.arguments.single()
+
+        if (parent !is ArgumentHolder) {
+            log.error(
+                "Parent AST node of call expression is not an argument holder. Cannot convert to cast expression. Further analysis might not be entirely accurate."
+            )
+            return
+        }
+
+        val success = parent.replaceArgument(call, cast)
+        if (!success) {
+            log.error(
+                "Replacing call expression with cast expression was not successful. Further analysis might not be entirely accurate."
+            )
+        } else {
+            call.disconnectFromGraph()
+        }
+    }
+
+    override fun cleanup() {
+        // Nothing to do
+    }
+}