feat: scoping for member accesses if receiver has type parameter type (…

…#889)

### Summary of Changes

The scope provider can now handle member accesses where the receiver has
type parameter type. This type is replaced by its upper bound, before
name resolution continues as before.

packages/safe-ds-lang/src/language/scoping/safe-ds-scope-provider.ts

@@ -71,7 +71,7 @@ import {
 } from '../helpers/nodeProperties.js';
 import { SafeDsNodeMapper } from '../helpers/safe-ds-node-mapper.js';
 import { SafeDsServices } from '../safe-ds-module.js';
-import { ClassType, EnumVariantType, LiteralType } from '../typing/model.js';
+import { ClassType, EnumVariantType, LiteralType, TypeParameterType } from '../typing/model.js';
 import type { SafeDsClassHierarchy } from '../typing/safe-ds-class-hierarchy.js';
 import { SafeDsTypeComputer } from '../typing/safe-ds-type-computer.js';
 import { SafeDsPackageManager } from '../workspace/safe-ds-package-manager.js';
@@ -227,6 +227,8 @@ export class SafeDsScopeProvider extends DefaultScopeProvider {
         let receiverType = this.typeComputer.computeType(node.receiver);
         if (receiverType instanceof LiteralType) {
             receiverType = this.typeComputer.computeClassTypeForLiteralType(receiverType);
+        } else if (receiverType instanceof TypeParameterType) {
+            receiverType = this.typeComputer.computeUpperBound(receiverType);
         }
 
         if (receiverType instanceof ClassType) {

packages/safe-ds-lang/tests/resources/scoping/member accesses/on type parameters/main.sdstest

@@ -0,0 +1,29 @@
+package tests.scoping.memberAccesses.onTypeParameters
+
+class C {
+    // $TEST$ target attribute
+    attr »a«: Int
+}
+
+class MyClass<Unbounded, UpperBound>(
+    unbounded: Unbounded,
+    upperBound: UpperBound,
+
+    // $TEST$ unresolved
+    p1: Any = unbounded.»a«,
+    // $TEST$ references attribute
+    p2: Any = upperBound.»a«,
+) where {
+    UpperBound sub C
+} {
+    attr unbounded: Unbounded
+    attr upperBound: UpperBound
+}
+
+segment mySegment(instance: MyClass<C, C>) {
+    // $TEST$ references attribute
+    instance.unbounded.»a«;
+
+    // $TEST$ references attribute
+    instance.upperBound.»a«;
+}