feat: clamp default values of parameter types to upper bound (#921)

### Summary of Changes The default value of a type parameter is now clamped to its upper bound during inference of type parameters for calls.
Safe-DS · Feb 25, 2024 · 76ad869 · 76ad869
1 parent 35dc826
commit 76ad869
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Showing 2 changed files with 17 additions and 7 deletions.
diff --git a/packages/safe-ds-lang/src/language/typing/safe-ds-type-computer.ts b/packages/safe-ds-lang/src/language/typing/safe-ds-type-computer.ts
@@ -832,25 +832,29 @@ export class SafeDsTypeComputer {
 
         // Normalize substitutions
         for (const [typeParameter, substitution] of state.substitutions) {
+            let newSubstitution = substitution;
+
             // Replace unknown types by default values or lower bound (Nothing)
-            if (substitution === UnknownType) {
+            if (newSubstitution === UnknownType) {
                 const defaultValueType = this.computeType(typeParameter.defaultValue);
                 if (defaultValueType === UnknownType) {
                     state.substitutions.set(typeParameter, this.coreTypes.Nothing);
+                    continue;
                 } else {
-                    state.substitutions.set(typeParameter, defaultValueType);
+                    newSubstitution = defaultValueType;
                 }
-                continue;
             }
 
             // Clamp to upper bound
             const upperBound = this.computeUpperBound(typeParameter, {
                 stopAtTypeParameterType: true,
             }).substituteTypeParameters(state.substitutions);
 
-            if (!this.typeChecker.isSubtypeOf(substitution, upperBound)) {
-                state.substitutions.set(typeParameter, upperBound);
+            if (!this.typeChecker.isSubtypeOf(newSubstitution, upperBound)) {
+                newSubstitution = upperBound;
             }
+
+            state.substitutions.set(typeParameter, newSubstitution);
         }
 
         return state.substitutions;

diff --git a/...urces/typing/expressions/calls/type parameter inference/clamp to upper bound/main.sdstest b/...urces/typing/expressions/calls/type parameter inference/clamp to upper bound/main.sdstest
@@ -1,13 +1,19 @@
 package tests.typing.expressions.calls.typeParameterInference.clampToUpperBound
 
-class C1<T sub Int>(p1: T)
+class C1<T sub Int = String>(p1: T)
 
-@Pure fun f1<T sub Int>(p1: T) -> r1: T
+@Pure fun f1<T sub Int = String>(p1: T) -> r1: T
 
 pipeline myPipeline {
     // $TEST$ serialization C1<Int>
     »C1("")«;
 
+    // $TEST$ serialization C1<Int>
+    »C1()«;
+
     // $TEST$ serialization Int
     »f1("")«;
+
+    // $TEST$ serialization Int
+    »f1()«;
 }