From 2031708e406e2a21e8ab5a48db9e7ffa57c0ab83 Mon Sep 17 00:00:00 2001
From: Lars Reimann <mail@larsreimann.com>
Date: Sun, 25 Feb 2024 12:08:01 +0100
Subject: [PATCH] feat: type check type arguments of named types

---
 .../language/validation/safe-ds-validator.ts  |  2 +
 .../src/language/validation/types.ts          | 38 +++++++++++++++++++
 .../main.sdstest                              | 29 ++++++++++++++
 3 files changed, 69 insertions(+)
 create mode 100644 packages/safe-ds-lang/tests/resources/validation/types/checking/type parameter bounds for named types/main.sdstest

diff --git a/packages/safe-ds-lang/src/language/validation/safe-ds-validator.ts b/packages/safe-ds-lang/src/language/validation/safe-ds-validator.ts
index dcc88c864..1bd88d35f 100644
--- a/packages/safe-ds-lang/src/language/validation/safe-ds-validator.ts
+++ b/packages/safe-ds-lang/src/language/validation/safe-ds-validator.ts
@@ -166,6 +166,7 @@ import {
     listMustNotContainNamedTuples,
     mapMustNotContainNamedTuples,
     namedTypeMustSetAllTypeParameters,
+    namedTypeTypeArgumentsMustMatchBounds,
     parameterDefaultValueTypeMustMatchParameterType,
     parameterMustHaveTypeHint,
     prefixOperationOperandMustHaveCorrectType,
@@ -314,6 +315,7 @@ export const registerValidationChecks = function (services: SafeDsServices) {
             namedTypeMustSetAllTypeParameters(services),
             namedTypeTypeArgumentListShouldBeNeeded(services),
             namedTypeTypeArgumentListMustNotHavePositionalArgumentsAfterNamedArguments,
+            namedTypeTypeArgumentsMustMatchBounds(services),
         ],
         SdsParameter: [
             constantParameterMustHaveConstantDefaultValue(services),
diff --git a/packages/safe-ds-lang/src/language/validation/types.ts b/packages/safe-ds-lang/src/language/validation/types.ts
index f9515e110..75ea66e0b 100644
--- a/packages/safe-ds-lang/src/language/validation/types.ts
+++ b/packages/safe-ds-lang/src/language/validation/types.ts
@@ -252,6 +252,44 @@ export const mapMustNotContainNamedTuples = (services: SafeDsServices) => {
     };
 };
 
+export const namedTypeTypeArgumentsMustMatchBounds = (services: SafeDsServices) => {
+    const nodeMapper = services.helpers.NodeMapper;
+    const typeChecker = services.types.TypeChecker;
+    const typeComputer = services.types.TypeComputer;
+
+    return (node: SdsNamedType, accept: ValidationAcceptor): void => {
+        const type = typeComputer.computeType(node);
+        if (!(type instanceof ClassType) || isEmpty(type.substitutions)) {
+            return;
+        }
+
+        for (const typeArgument of getTypeArguments(node)) {
+            const typeParameter = nodeMapper.typeArgumentToTypeParameter(typeArgument);
+            if (!typeParameter) {
+                continue;
+            }
+
+            const typeArgumentType = type.substitutions.get(typeParameter);
+            if (!typeArgumentType) {
+                /* c8 ignore next 2 */
+                continue;
+            }
+
+            const upperBound = typeComputer
+                .computeUpperBound(typeParameter, { stopAtTypeParameterType: true })
+                .substituteTypeParameters(type.substitutions);
+
+            if (!typeChecker.isSubtypeOf(typeArgumentType, upperBound, { strictTypeParameterTypeCheck: true })) {
+                accept('error', `Expected type '${upperBound}' but got '${typeArgumentType}'.`, {
+                    node: typeArgument,
+                    property: 'value',
+                    code: CODE_TYPE_MISMATCH,
+                });
+            }
+        }
+    };
+};
+
 export const parameterDefaultValueTypeMustMatchParameterType = (services: SafeDsServices) => {
     const typeChecker = services.types.TypeChecker;
     const typeComputer = services.types.TypeComputer;
diff --git a/packages/safe-ds-lang/tests/resources/validation/types/checking/type parameter bounds for named types/main.sdstest b/packages/safe-ds-lang/tests/resources/validation/types/checking/type parameter bounds for named types/main.sdstest
new file mode 100644
index 000000000..d0524371e
--- /dev/null
+++ b/packages/safe-ds-lang/tests/resources/validation/types/checking/type parameter bounds for named types/main.sdstest	
@@ -0,0 +1,29 @@
+package tests.validation.types.checking.typeParameterBoundsForNamedTypes
+
+class C1<T1>
+class C2<T1 sub Number>
+class C3<T1, T2 sub T1>
+
+@Pure fun f(
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    a1: C1<»Any?«>,
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    a2: C1<T1 = »Any?«>,
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    a3: C1<Unknown = »Any?«>,
+
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    b1: C2<»Number«>,
+    // $TEST$ error "Expected type 'Number' but got 'String'."
+    b2: C2<»String«>,
+
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    c1: C3<»Number«, »Number«>,
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    c2: C3<»Number«, »Int«>,
+    // $TEST$ no error r"Expected type '.*' but got '.*'\."
+    // $TEST$ error "Expected type 'Int' but got 'Number'."
+    c3: C3<»Int«, »Number«>,
+)