feat: show info that empty constraint lists can be removed (#572)

Closes #570

### Summary of Changes

Show an info if a constraint list is empty.

---------

Co-authored-by: megalinter-bot <129584137+megalinter-bot@users.noreply.github.com>

src/language/validation/safe-ds-validator.ts

@@ -6,13 +6,12 @@ import {
     annotationParameterListShouldNotBeEmpty,
     assignmentShouldHaveMoreThanWildcardsAsAssignees,
     classBodyShouldNotBeEmpty,
-    classTypeParameterListShouldNotBeEmpty,
+    constraintListShouldNotBeEmpty,
     enumBodyShouldNotBeEmpty,
     enumVariantParameterListShouldNotBeEmpty,
-    enumVariantTypeParameterListShouldNotBeEmpty,
     functionResultListShouldNotBeEmpty,
-    functionTypeParameterListShouldNotBeEmpty,
     segmentResultListShouldNotBeEmpty,
+    typeParameterListShouldNotBeEmpty,
     unionTypeShouldNotHaveASingularTypeArgument,
 } from './style.js';
 import { templateStringMustHaveExpressionBetweenTwoStringParts } from './other/expressions/templateStrings.js';
@@ -31,17 +30,19 @@ export const registerValidationChecks = function (services: SafeDsServices) {
         SdsAssignment: [assignmentShouldHaveMoreThanWildcardsAsAssignees],
         SdsAnnotation: [annotationParameterListShouldNotBeEmpty],
         SdsAttribute: [attributeMustHaveTypeHint],
-        SdsClass: [classBodyShouldNotBeEmpty, classTypeParameterListShouldNotBeEmpty],
+        SdsClassBody: [classBodyShouldNotBeEmpty],
+        SdsConstraintList: [constraintListShouldNotBeEmpty],
         SdsDeclaration: [nameMustNotStartWithBlockLambdaPrefix, nameShouldHaveCorrectCasing],
-        SdsEnum: [enumBodyShouldNotBeEmpty],
-        SdsEnumVariant: [enumVariantParameterListShouldNotBeEmpty, enumVariantTypeParameterListShouldNotBeEmpty],
-        SdsFunction: [functionResultListShouldNotBeEmpty, functionTypeParameterListShouldNotBeEmpty],
+        SdsEnumBody: [enumBodyShouldNotBeEmpty],
+        SdsEnumVariant: [enumVariantParameterListShouldNotBeEmpty],
+        SdsFunction: [functionResultListShouldNotBeEmpty],
         SdsModule: [moduleDeclarationsMustMatchFileKind, moduleWithDeclarationsMustStatePackage],
         SdsParameter: [parameterMustHaveTypeHint],
         SdsResult: [resultMustHaveTypeHint],
         SdsSegment: [segmentResultListShouldNotBeEmpty],
         SdsTemplateString: [templateStringMustHaveExpressionBetweenTwoStringParts],
         SdsTypeParameterConstraint: [typeParameterConstraintLeftOperandMustBeOwnTypeParameter],
+        SdsTypeParameterList: [typeParameterListShouldNotBeEmpty],
         SdsUnionType: [unionTypeShouldNotHaveASingularTypeArgument],
         SdsYield: [yieldMustNotBeUsedInPipeline],
     };

src/language/validation/style.ts

@@ -2,11 +2,13 @@ import {
     isSdsWildcard,
     SdsAnnotation,
     SdsAssignment,
-    SdsClass,
-    SdsEnum,
+    SdsClassBody,
+    SdsConstraintList,
+    SdsEnumBody,
     SdsEnumVariant,
     SdsFunction,
     SdsSegment,
+    SdsTypeParameterList,
     SdsUnionType,
 } from '../generated/ast.js';
 import { ValidationAcceptor } from 'langium';
@@ -15,6 +17,7 @@ import { isEmpty } from 'radash';
 export const CODE_STYLE_UNNECESSARY_ASSIGNMENT = 'style/unnecessary-assignment';
 export const CODE_STYLE_UNNECESSARY_ARGUMENT_LIST = 'style/unnecessary-argument-list';
 export const CODE_STYLE_UNNECESSARY_BODY = 'style/unnecessary-body';
+export const CODE_STYLE_UNNECESSARY_CONSTRAINT_LIST = 'style/unnecessary-constraint-list';
 export const CODE_STYLE_UNNECESSARY_ELVIS_OPERATOR = 'style/unnecessary-elvis-operator';
 export const CODE_STYLE_UNNECESSARY_SAFE_ACCESS = 'style/unnecessary-safe-access';
 export const CODE_STYLE_UNNECESSARY_PARAMETER_LIST = 'style/unnecessary-parameter-list';
@@ -44,26 +47,37 @@ export const assignmentShouldHaveMoreThanWildcardsAsAssignees = (
 // Unnecessary bodies
 // -----------------------------------------------------------------------------
 
-export const classBodyShouldNotBeEmpty = (node: SdsClass, accept: ValidationAcceptor) => {
-    if (node.body && isEmpty(node.body.members)) {
+export const classBodyShouldNotBeEmpty = (node: SdsClassBody, accept: ValidationAcceptor) => {
+    if (isEmpty(node.members)) {
         accept('info', 'This body can be removed.', {
             node,
-            property: 'body',
             code: CODE_STYLE_UNNECESSARY_BODY,
         });
     }
 };
 
-export const enumBodyShouldNotBeEmpty = (node: SdsEnum, accept: ValidationAcceptor) => {
-    if (node.body && isEmpty(node.body.variants)) {
+export const enumBodyShouldNotBeEmpty = (node: SdsEnumBody, accept: ValidationAcceptor) => {
+    if (isEmpty(node.variants)) {
         accept('info', 'This body can be removed.', {
             node,
-            property: 'body',
             code: CODE_STYLE_UNNECESSARY_BODY,
         });
     }
 };
 
+// -----------------------------------------------------------------------------
+// Unnecessary constraint list
+// -----------------------------------------------------------------------------
+
+export const constraintListShouldNotBeEmpty = (node: SdsConstraintList, accept: ValidationAcceptor) => {
+    if (isEmpty(node.constraints)) {
+        accept('info', 'This constraint list can be removed.', {
+            node,
+            code: CODE_STYLE_UNNECESSARY_CONSTRAINT_LIST,
+        });
+    }
+};
+
 // -----------------------------------------------------------------------------
 // Unnecessary parameter lists
 // -----------------------------------------------------------------------------
@@ -116,31 +130,10 @@ export const segmentResultListShouldNotBeEmpty = (node: SdsSegment, accept: Vali
 // Unnecessary type parameter lists
 // -----------------------------------------------------------------------------
 
-export const classTypeParameterListShouldNotBeEmpty = (node: SdsClass, accept: ValidationAcceptor) => {
-    if (node.typeParameterList && isEmpty(node.typeParameterList.typeParameters)) {
-        accept('info', 'This type parameter list can be removed.', {
-            node,
-            property: 'typeParameterList',
-            code: CODE_STYLE_UNNECESSARY_TYPE_PARAMETER_LIST,
-        });
-    }
-};
-
-export const enumVariantTypeParameterListShouldNotBeEmpty = (node: SdsEnumVariant, accept: ValidationAcceptor) => {
-    if (node.typeParameterList && isEmpty(node.typeParameterList.typeParameters)) {
-        accept('info', 'This type parameter list can be removed.', {
-            node,
-            property: 'typeParameterList',
-            code: CODE_STYLE_UNNECESSARY_TYPE_PARAMETER_LIST,
-        });
-    }
-};
-
-export const functionTypeParameterListShouldNotBeEmpty = (node: SdsFunction, accept: ValidationAcceptor) => {
-    if (node.typeParameterList && isEmpty(node.typeParameterList.typeParameters)) {
+export const typeParameterListShouldNotBeEmpty = (node: SdsTypeParameterList, accept: ValidationAcceptor) => {
+    if (isEmpty(node.typeParameters)) {
         accept('info', 'This type parameter list can be removed.', {
             node,
-            property: 'typeParameterList',
             code: CODE_STYLE_UNNECESSARY_TYPE_PARAMETER_LIST,
         });
     }

tests/resources/validation/style/unnecessary constraint list in annotation/main.sdstest

@@ -0,0 +1,9 @@
+package tests.validation.style.unnecessaryConstraintListInAnnotation
+
+// $TEST$ info "This constraint list can be removed."
+annotation MyAnnotation1 »where {}«
+
+// $TEST$ no info "This constraint list can be removed."
+annotation MyAnnotation2 »where {
+    T sub Int
+}«

tests/resources/validation/style/unnecessary constraint list in class/main.sdstest

@@ -0,0 +1,9 @@
+package tests.validation.style.unnecessaryConstraintListInClass
+
+// $TEST$ info "This constraint list can be removed."
+class MyClass1 »where {}«
+
+// $TEST$ no info "This constraint list can be removed."
+class MyClass2<T> »where {
+    T sub Int
+}«

tests/resources/validation/style/unnecessary constraint list in enum variant/main.sdstest

@@ -0,0 +1,11 @@
+package tests.validation.style.unnecessaryConstraintInEnumVariant
+
+enum MyEnum {
+    // $TEST$ info "This constraint list can be removed."
+    MyVariant1 »where {}«
+
+    // $TEST$ no info "This constraint list can be removed."
+    MyVariant2<T>() »where {
+        T sub Int
+    }«
+}

tests/resources/validation/style/unnecessary constraint list in function/main.sdstest

@@ -0,0 +1,9 @@
+package tests.validation.style.unnecessaryConstraintListInFunction
+
+// $TEST$ info "This constraint list can be removed."
+fun myFunction1() »where {}«
+
+// $TEST$ no info "This constraint list can be removed."
+fun myFunction2<T>() »where {
+    T sub Int
+}«