feat: annotations for the purity of functions (#709)

Closes #559

### Summary of Changes

Add annotations to denote the purity of functions to the builtin
library.

packages/safe-ds-lang/src/resources/builtins/safeds/lang/purity.sdsstub

@@ -10,3 +10,53 @@ package safeds.lang
 @Experimental
 @Target([AnnotationTarget.Function])
 annotation Pure
+
+/**
+ * Indicates that the function has side effects and/or does not always return the same results given the same arguments.
+ *
+ * @param allReasons
+ *     A list of **all** reasons why the function is impure. If no specific {@link ImpurityReason} applies, include
+ *     `ImpurityReason.Other`.
+ */
+@Experimental
+@Target([AnnotationTarget.Function])
+annotation Impure(allReasons: List<ImpurityReason>)
+
+/**
+ * A reason why a function is impure.
+ */
+enum ImpurityReason {
+
+    /**
+     * The function reads from a file and the file path is a constant.
+     *
+     * @param path The path of the file.
+     */
+    FileReadFromConstantPath(path: String)
+
+    /**
+     * The function reads from a file and the file path is given by a parameter.
+     *
+     * @param parameterName The name of the parameter that specifies the file path.
+     */
+    FileReadFromParameterizedPath(parameterName: String)
+
+    /**
+     * The function writes to a file and the file path is a constant.
+     *
+     * @param path The path of the file.
+     */
+    FileWriteToConstantPath(path: String)
+
+    /**
+     * The function writes to a file and the file path is given by a parameter.
+     *
+     * @param parameterName The name of the parameter that specifies the file path.
+     */
+    FileWriteToParameterizedPath(parameterName: String)
+
+    /**
+     * The function is impure for some other reason. If possible, use a more specific reason.
+     */
+    Other
+}

packages/safe-ds-lang/tests/language/generation/testGeneration.test.ts → packages/safe-ds-lang/tests/language/generation/safe-ds-python-generator.test.ts

@@ -1,4 +1,4 @@
-import { createSafeDsServices } from '../../../src/language/safe-ds-module.js';
+import { createSafeDsServices } from '../../../src/language/index.js';
 import { clearDocuments } from 'langium/test';
 import { afterEach, beforeEach, describe, expect, it } from 'vitest';
 import { NodeFileSystem } from 'langium/node';

packages/safe-ds-lang/tests/language/grammar/testGrammar.test.ts → packages/safe-ds-lang/tests/language/grammar/safe-ds-grammar.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, describe, it } from 'vitest';
-import { createSafeDsServices } from '../../../src/language/safe-ds-module.js';
+import { createSafeDsServices } from '../../../src/language/index.js';
 import { AssertionError } from 'assert';
 import { NodeFileSystem } from 'langium/node';
 import { createGrammarTests } from './creator.js';

packages/safe-ds-lang/tests/language/grammar/safe-ds-value-converter.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest';
-import { createSafeDsServices } from '../../../src/language/safe-ds-module.js';
+import { createSafeDsServices } from '../../../src/language/index.js';
 import { EmptyFileSystem } from 'langium';
 import { getNodeOfType } from '../../helpers/nodeFinder.js';
 import {

packages/safe-ds-lang/tests/language/lsp/formatting/testFormatting.test.ts → packages/safe-ds-lang/tests/language/lsp/formatting/safe-ds-formatter.test.ts

@@ -1,4 +1,4 @@
-import { createSafeDsServices } from '../../../../src/language/safe-ds-module.js';
+import { createSafeDsServices } from '../../../../src/language/index.js';
 import { clearDocuments, expectFormatting } from 'langium/test';
 import { afterEach, describe, it } from 'vitest';
 import { EmptyFileSystem } from 'langium';

packages/safe-ds-lang/tests/language/scoping/testScoping.test.ts → packages/safe-ds-lang/tests/language/scoping/scoping.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, beforeEach, describe, it } from 'vitest';
-import { createSafeDsServices } from '../../../src/language/safe-ds-module.js';
+import { createSafeDsServices } from '../../../src/language/index.js';
 import { LangiumDocument, Reference, URI } from 'langium';
 import { NodeFileSystem } from 'langium/node';
 import { clearDocuments, isRangeEqual } from 'langium/test';

packages/safe-ds-lang/tests/language/typing/type computer/testTyping.test.ts → packages/safe-ds-lang/tests/language/typing/type computer/safe-ds-type-computer.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, beforeEach, describe, it } from 'vitest';
-import { createSafeDsServices } from '../../../../src/language/safe-ds-module.js';
+import { createSafeDsServices } from '../../../../src/language/index.js';
 import { NodeFileSystem } from 'langium/node';
 import { clearDocuments } from 'langium/test';
 import { AssertionError } from 'assert';

packages/safe-ds-lang/tests/language/validation/testValidation.test.ts → packages/safe-ds-lang/tests/language/validation/safe-ds-validator.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, beforeEach, describe, it } from 'vitest';
-import { createSafeDsServices } from '../../../src/language/safe-ds-module.js';
+import { createSafeDsServices } from '../../../src/language/index.js';
 import { NodeFileSystem } from 'langium/node';
 import { createValidationTests, ExpectedIssue } from './creator.js';
 import { Diagnostic, DiagnosticSeverity } from 'vscode-languageserver';