feat: show info that empty constraint lists can be removed

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

@@ -1,23 +1,25 @@
-import { ValidationChecks } from 'langium';
-import { SafeDsAstType } from '../generated/ast.js';
-import type { SafeDsServices } from '../safe-ds-module.js';
-import { nameMustNotStartWithBlockLambdaPrefix, nameShouldHaveCorrectCasing } from './names.js';
+import {ValidationChecks} from 'langium';
+import {SafeDsAstType} from '../generated/ast.js';
+import type {SafeDsServices} from '../safe-ds-module.js';
+import {nameMustNotStartWithBlockLambdaPrefix, nameShouldHaveCorrectCasing} from './names.js';
 import {
     annotationParameterListShouldNotBeEmpty,
     assignmentShouldHaveMoreThanWildcardsAsAssignees,
-    classBodyShouldNotBeEmpty,
+    classBodyShouldNotBeEmpty, constraintListShouldNotBeEmpty,
     enumBodyShouldNotBeEmpty,
     enumVariantParameterListShouldNotBeEmpty,
     functionResultListShouldNotBeEmpty,
     segmentResultListShouldNotBeEmpty,
     typeParameterListShouldNotBeEmpty,
     unionTypeShouldNotHaveASingularTypeArgument,
 } from './style.js';
-import { templateStringMustHaveExpressionBetweenTwoStringParts } from './other/expressions/templateStrings.js';
-import { yieldMustNotBeUsedInPipeline } from './other/statements/assignments.js';
-import { attributeMustHaveTypeHint, parameterMustHaveTypeHint, resultMustHaveTypeHint } from './types.js';
-import { moduleDeclarationsMustMatchFileKind, moduleWithDeclarationsMustStatePackage } from './other/modules.js';
-import { typeParameterConstraintLeftOperandMustBeOwnTypeParameter } from './other/declarations/typeParameterConstraints.js';
+import {templateStringMustHaveExpressionBetweenTwoStringParts} from './other/expressions/templateStrings.js';
+import {yieldMustNotBeUsedInPipeline} from './other/statements/assignments.js';
+import {attributeMustHaveTypeHint, parameterMustHaveTypeHint, resultMustHaveTypeHint} from './types.js';
+import {moduleDeclarationsMustMatchFileKind, moduleWithDeclarationsMustStatePackage} from './other/modules.js';
+import {
+    typeParameterConstraintLeftOperandMustBeOwnTypeParameter
+} from './other/declarations/typeParameterConstraints.js';
 
 /**
  * Register custom validation checks.
@@ -30,6 +32,7 @@ export const registerValidationChecks = function (services: SafeDsServices) {
         SdsAnnotation: [annotationParameterListShouldNotBeEmpty],
         SdsAttribute: [attributeMustHaveTypeHint],
         SdsClassBody: [classBodyShouldNotBeEmpty],
+        SdsConstraintList: [constraintListShouldNotBeEmpty],
         SdsDeclaration: [nameMustNotStartWithBlockLambdaPrefix, nameShouldHaveCorrectCasing],
         SdsEnumBody: [enumBodyShouldNotBeEmpty],
         SdsEnumVariant: [enumVariantParameterListShouldNotBeEmpty],
@@ -50,4 +53,5 @@ export const registerValidationChecks = function (services: SafeDsServices) {
 /**
  * Implementation of custom validations.
  */
-export class SafeDsValidator {}
+export class SafeDsValidator {
+}

src/language/validation/style.ts

@@ -3,6 +3,7 @@ import {
     SdsAnnotation,
     SdsAssignment,
     SdsClassBody,
+    SdsConstraintList,
     SdsEnumBody,
     SdsEnumVariant,
     SdsFunction,
@@ -16,6 +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';
@@ -63,6 +65,19 @@ export const enumBodyShouldNotBeEmpty = (node: SdsEnumBody, accept: ValidationAc
     }
 };
 
+// -----------------------------------------------------------------------------
+// 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
 // -----------------------------------------------------------------------------

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
+}«