feat: error if function pointers are used (#629)

Closes #565
Closes partially #543

### Summary of Changes

To provide a cleaner graphical view, this PR makes the use of function
pointers (to functions/segments) an error. Lambdas can be used instead.

---------

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

src/language/validation/other/expressions/references.ts

@@ -1,8 +1,42 @@
-import { isSdsAnnotation, isSdsPipeline, isSdsSchema, SdsReference } from '../../../generated/ast.js';
-import { ValidationAcceptor } from 'langium';
+import {
+ isSdsAnnotation,
+ isSdsCall,
+ isSdsFunction,
+ isSdsMemberAccess,
+ isSdsPipeline,
+ isSdsSchema,
+ isSdsSegment,
+ SdsReference,
+} from '../../../generated/ast.js';
+import { AstNode, ValidationAcceptor } from 'langium';
 
+export const CODE_REFERENCE_FUNCTION_POINTER = 'reference/function-pointer';
 export const CODE_REFERENCE_TARGET = 'reference/target';
 
+export const referenceMustNotBeFunctionPointer = (node: SdsReference, accept: ValidationAcceptor): void => {
+ const target = node.target?.ref;
+ if (!isSdsFunction(target) && !isSdsSegment(target)) {
+ return;
+ }
+
+ //
+ let container: AstNode | undefined = node.$container;
+ if (isSdsMemberAccess(container) && node.$containerProperty === 'member') {
+ container = container.$container;
+ }
+
+ if (!isSdsCall(container)) {
+ accept(
+ 'error',
+ 'Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead.',
+ {
+ node,
+ code: CODE_REFERENCE_FUNCTION_POINTER,
+ },
+ );
+ }
+};
+
 export const referenceTargetMustNotBeAnnotationPipelineOrSchema = (
  node: SdsReference,
  accept: ValidationAcceptor,

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

@@ -45,7 +45,10 @@ import {
 } from './other/types/callableTypes.js';
 import { typeArgumentListMustNotHavePositionalArgumentsAfterNamedArguments } from './other/types/typeArgumentLists.js';
 import { argumentListMustNotHavePositionalArgumentsAfterNamedArguments } from './other/argumentLists.js';
-import { referenceTargetMustNotBeAnnotationPipelineOrSchema } from './other/expressions/references.js';
+import {
+ referenceMustNotBeFunctionPointer,
+ referenceTargetMustNotBeAnnotationPipelineOrSchema,
+} from './other/expressions/references.js';
 import {
  annotationCallAnnotationShouldNotBeDeprecated,
  argumentCorrespondingParameterShouldNotBeDeprecated,
@@ -141,6 +144,7 @@ export const registerValidationChecks = function (services: SafeDsServices) {
  SdsPipeline: [pipelineMustContainUniqueNames],
  SdsPlaceholder: [placeholdersMustNotBeAnAlias, placeholderShouldBeUsed(services)],
  SdsReference: [
+ referenceMustNotBeFunctionPointer,
  referenceTargetMustNotBeAnnotationPipelineOrSchema,
  referenceTargetShouldNotBeDeprecated(services),
  referenceTargetShouldNotExperimental(services),

tests/resources/validation/other/expressions/references/function pointer/main.sdstest

@@ -0,0 +1,68 @@
+package tests.validation.other.expressions.references.target
+
+class MyClass {
+ fun myInstanceMethod()
+ static fun myStaticMethod()
+}
+
+fun myFunction1()
+fun myFunction2(p: Any)
+
+segment mySegment1() {}
+
+segment mySegment2() {
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ MyClass().»myInstanceMethod«;
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ MyClass().»myInstanceMethod«.a;
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ MyClass().»myInstanceMethod«.a();
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ myFunction2(MyClass().»myInstanceMethod«);
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ MyClass().»myInstanceMethod«();
+
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ MyClass.»myStaticMethod«;
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ MyClass.»myStaticMethod«.a;
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ MyClass.»myStaticMethod«.a();
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ myFunction2(MyClass.»myStaticMethod«);
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ MyClass.»myStaticMethod«();
+
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »myFunction1«;
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »myFunction1«.a;
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »myFunction1«.a();
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ myFunction2(»myFunction1«);
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »myFunction1«();
+
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »mySegment1«;
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »mySegment1«.a;
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »mySegment1«.a();
+ // $TEST$ error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ myFunction2(»mySegment1«);
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »mySegment1«();
+
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »unresolved«;
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »unresolved«.a;
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »unresolved«.a();
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ myFunction2(»unresolved«);
+ // $TEST$ no error "Function pointers are not allowed to provide a cleaner graphical view. Use a lambda instead."
+ »unresolved«();
+}