feat: prefix keywords with ^ to treat them as identifiers (#1172)

### Summary of Changes

Keywords can now be prefixed with `^` to treat them as identifiers.
Previously, they had to be surrounded by backticks. The hat prefix is
more readable and shorter

docs/src/lexer/safe_ds_lexer/_safe_ds_lexer.py

@@ -68,7 +68,7 @@
 )
 
 identifier_fragment = r"[_a-zA-Z][_a-zA-Z0-9]*"
-identifier_regex = rf"{identifier_fragment}|`{identifier_fragment}`"
+identifier_regex = rf"{identifier_fragment}|^{identifier_fragment}"
 qualified_name_regex = rf"({identifier_regex})(\.({identifier_regex}))*"
 
 

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

@@ -4,7 +4,7 @@ export class SafeDsValueConverter extends DefaultValueConverter {
     protected override runConverter(rule: GrammarAST.AbstractRule, input: string, cstNode: CstNode): ValueType {
         switch (rule.name.toUpperCase()) {
             case 'ID':
-                return input.replaceAll('`', '');
+                return input.replace(/^\^/u, '');
             case 'INT':
                 return ValueConverter.convertBigint(input);
             case 'STRING':

packages/safe-ds-lang/src/language/grammar/safe-ds.langium

@@ -1097,7 +1097,7 @@ SdsColumn returns SdsColumn:
 // Terminals
 // -----------------------------------------------------------------------------
 
-terminal ID returns string: IDENTIFIER | '`' IDENTIFIER '`';
+terminal ID returns string: IDENTIFIER | '^' IDENTIFIER;
 terminal fragment IDENTIFIER: /[_a-zA-Z][_a-zA-Z0-9]*/;
 
 terminal FLOAT returns number

packages/safe-ds-lang/src/language/validation/other/declarations/placeholders.ts

@@ -40,7 +40,7 @@ export const placeholdersMustNotBeAnAlias = (node: SdsPlaceholder, accept: Valid
 export const placeholderShouldBeUsed =
     (services: SafeDsServices) => (node: SdsPlaceholder, accept: ValidationAcceptor) => {
         // Don't a warning if the placeholder's name starts with an underscore
-        if (node.name.startsWith('_')) {
+        if (!node.name || node.name.startsWith('_')) {
             return;
         }
 

packages/safe-ds-lang/src/resources/builtins/safeds/data/tabular/containers/ExperimentalCell.sdsstub

@@ -19,7 +19,7 @@ class ExperimentalCell<T = Any?> {
      */
     @Pure
     @PythonName("not_")
-    fun `not`() -> result: ExperimentalCell<Boolean>
+    fun ^not() -> result: ExperimentalCell<Boolean>
 
     /**
      * Perform a boolean AND operation. This is equivalent to the `&` operator.
@@ -33,7 +33,7 @@ class ExperimentalCell<T = Any?> {
      */
     @Pure
     @PythonName("and_")
-    fun `and`(
+    fun ^and(
         other: union<Boolean, ExperimentalCell<Boolean>>
     ) -> result: ExperimentalCell<Boolean>
 
@@ -49,7 +49,7 @@ class ExperimentalCell<T = Any?> {
      */
     @Pure
     @PythonName("or_")
-    fun `or`(
+    fun ^or(
         other: union<Boolean, ExperimentalCell<Boolean>>
     ) -> result: ExperimentalCell<Boolean>
 
@@ -191,7 +191,7 @@ class ExperimentalCell<T = Any?> {
      * }
      */
     @Pure
-    fun `sub`(
+    fun ^sub(
         other: Any
     ) -> result: ExperimentalCell
 

packages/safe-ds-lang/src/resources/builtins/safeds/data/tabular/containers/ExperimentalRow.sdsstub

@@ -21,7 +21,7 @@ class ExperimentalRow {
     /**
      * The schema of the row.
      */
-    attr `schema`: ExperimentalSchema
+    attr ^schema: ExperimentalSchema
 
     /**
      * Get the value of the specified column.

packages/safe-ds-lang/src/resources/builtins/safeds/data/tabular/containers/ExperimentalTable.sdsstub

@@ -55,7 +55,7 @@ class ExperimentalTable(
     /**
      * The schema of the table.
      */
-    attr `schema`: ExperimentalSchema
+    attr ^schema: ExperimentalSchema
 
     /**
      * Create a table from a list of columns.

packages/safe-ds-lang/src/resources/builtins/safeds/data/tabular/containers/Row.sdsstub

@@ -47,10 +47,10 @@ class Row(
      * @example
      * pipeline example {
      *     val row = Row({"a": 1, "b": 2});
-     *     val `schema` = row.`schema`;
+     *     val ^schema = row.^schema;
      * }
      */
-    attr `schema`: Schema
+    attr ^schema: Schema
 
     /**
      * Create a row from a dictionary that maps column names to column values.

packages/safe-ds-lang/src/resources/builtins/safeds/data/tabular/containers/Table.sdsstub

@@ -67,10 +67,10 @@ class Table(
      * @example
      * pipeline example {
      *     val table = Table({"a": [1, 2], "b": [3, 4]});
-     *     val `schema` = table.`schema`;
+     *     val ^schema = table.^schema;
      * }
      */
-    attr `schema`: Schema
+    attr ^schema: Schema
 
     /**
      * Read data from a CSV file into a table.

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

@@ -17,18 +17,18 @@ const services = (await createSafeDsServices(EmptyFileSystem, { omitBuiltins: tr
 
 describe('runConverter', () => {
     describe('ID', () => {
-        it('should remove backticks (package)', async () => {
+        it('should remove hat (package)', async () => {
             const code = `
-                package \`foo\`.bar
+                package ^foo.bar
             `;
 
             const module = await getNodeOfType(services, code, isSdsModule);
             expect(module.name).toBe('foo.bar');
         });
 
-        it('should remove backticks (declaration)', async () => {
+        it('should remove hat (declaration)', async () => {
             const code = `
-                class \`MyClass\`
+                class ^MyClass
             `;
 
             const firstClass = await getNodeOfType(services, code, isSdsClass);

packages/safe-ds-lang/tests/resources/call graph/block lambda call/argument/segment.sdsdev

@@ -1,4 +1,4 @@
-package tests.callGraph.blockLambdaCall.argument.`segment`
+package tests.callGraph.blockLambdaCall.argument.^segment
 
 @Pure fun f()
 

packages/safe-ds-lang/tests/resources/call graph/callable/class.sdsdev

@@ -1,4 +1,4 @@
-package tests.callGraph.callable.`class`
+package tests.callGraph.callable.^class
 
 @Pure fun f() -> r: Any
 @Pure fun g()

packages/safe-ds-lang/tests/resources/call graph/callable/segment.sdsdev

@@ -1,4 +1,4 @@
-package tests.callGraph.callable.`segment`
+package tests.callGraph.callable.^segment
 
 @Pure fun f() -> r: Any
 @Pure fun g() -> r: Any

packages/safe-ds-lang/tests/resources/call graph/expression lambda call/argument/segment.sdsdev

@@ -1,4 +1,4 @@
-package tests.callGraph.expressionLambdaCall.argument.`segment`
+package tests.callGraph.expressionLambdaCall.argument.^segment
 
 @Pure fun f()
 

packages/safe-ds-lang/tests/resources/call graph/segment call/argument/segment.sdsdev

@@ -1,4 +1,4 @@
-package tests.callGraph.segmentCall.argument.`segment`
+package tests.callGraph.segmentCall.argument.^segment
 
 @Pure fun f()
 

packages/safe-ds-lang/tests/resources/generation/python/runner integration/expressions/this/input.sdsdev

@@ -1,4 +1,4 @@
-package tests.generator.runnerIntegration.expressions.`this`
+package tests.generator.runnerIntegration.expressions.^this
 
 class MyClass() {
     @Pure

packages/safe-ds-lang/tests/resources/grammar/keywords as names/good-escapedKeywords.sdsdev

@@ -1,35 +1,35 @@
 // $TEST$ no_syntax_error
 
-class `_`
-class `and`
-class `annotation`
-class `as`
-class `attr`
-class `class`
-class `const`
-class `enum`
-class `false`
-class `from`
-class `fun`
-class `import`
-class `in`
-class `internal`
-class `literal`
-class `not`
-class `null`
-class `or`
-class `out`
-class `package`
-class `pipeline`
-class `private`
-class `schema`
-class `static`
-class `segment`
-class `sub`
-class `this`
-class `true`
-class `union`
-class `unknown`
-class `val`
-class `where`
-class `yield`
+class ^_
+class ^and
+class ^annotation
+class ^as
+class ^attr
+class ^class
+class ^const
+class ^enum
+class ^false
+class ^from
+class ^fun
+class ^import
+class ^in
+class ^internal
+class ^literal
+class ^not
+class ^null
+class ^or
+class ^out
+class ^package
+class ^pipeline
+class ^private
+class ^schema
+class ^static
+class ^segment
+class ^sub
+class ^this
+class ^true
+class ^union
+class ^unknown
+class ^val
+class ^where
+class ^yield

packages/safe-ds-lang/tests/resources/grammar/keywords as names/good-escapedNonKeyword.sdsdev

@@ -1,3 +1,3 @@
 // $TEST$ no_syntax_error
 
-class `Bla`
+class ^Bla

packages/safe-ds-lang/tests/resources/partial evaluation/recursive cases/infix operations/and/main.sdsdev

@@ -1,4 +1,4 @@
-package tests.partialValidation.recursiveCases.infixOperations.`and`
+package tests.partialValidation.recursiveCases.infixOperations.^and
 
 pipeline test {
     // $TEST$ serialization false

packages/safe-ds-lang/tests/resources/partial evaluation/recursive cases/infix operations/and/short circuiting.sdsdev

@@ -1,4 +1,4 @@
-package tests.partialValidation.recursiveCases.infixOperations.`and`
+package tests.partialValidation.recursiveCases.infixOperations.^and
 
 @Pure
 fun pureFunction() -> result: Boolean

packages/safe-ds-lang/tests/resources/partial evaluation/recursive cases/infix operations/or/main.sdsdev

@@ -1,4 +1,4 @@
-package tests.partialValidation.recursiveCases.infixOperations.`or`
+package tests.partialValidation.recursiveCases.infixOperations.^or
 
 pipeline test {
     // $TEST$ serialization false

packages/safe-ds-lang/tests/resources/partial evaluation/recursive cases/infix operations/or/short circuiting.sdsdev

@@ -1,4 +1,4 @@
-package tests.partialValidation.recursiveCases.infixOperations.`or`
+package tests.partialValidation.recursiveCases.infixOperations.^or
 
 @Pure
 fun pureFunction() -> result: Boolean

packages/safe-ds-lang/tests/resources/partial evaluation/recursive cases/prefix operations/not/main.sdsdev

@@ -1,4 +1,4 @@
-package tests.partialValidation.recursiveCases.prefixOperations.`not`
+package tests.partialValidation.recursiveCases.prefixOperations.^not
 
 pipeline test {
     // $TEST$ serialization true

packages/safe-ds-lang/tests/resources/typing/expressions/this/main.sdsdev

@@ -1,4 +1,4 @@
-package tests.typing.expressions.`this`
+package tests.typing.expressions.^this
 
 // $TEST$ serialization unknown
 annotation MyAnnotation(p: Any? = »this«)

packages/safe-ds-lang/tests/resources/typing/highest common subtype/unhandled type/main.sdsdev

@@ -6,18 +6,18 @@ segment mySegment(
     one: Contravariant<literal<1>>,
     oneOrNull: Contravariant<literal<1, null>>,
 
-    `union`: Contravariant<union<Boolean, String>>,
+    ^union: Contravariant<union<Boolean, String>>,
     unionOrNull: Contravariant<union<Boolean, String?>>,
 
     callable: Contravariant<() -> ()>,
 
     // Named tuple types and static types are also not handled, but we can't test them here
 ) {
     // $TEST$ serialization List<Contravariant<Nothing>>
-    »[one, `union`]«;
+    »[one, ^union]«;
 
     // $TEST$ serialization List<Contravariant<Nothing>>
-    »[oneOrNull, `union`]«;
+    »[oneOrNull, ^union]«;
 
     // $TEST$ serialization List<Contravariant<Nothing>>
     »[one, unionOrNull]«;

packages/safe-ds-lang/tests/resources/validation/builtins/annotations/pythonMacro/main.sdsdev

@@ -7,7 +7,7 @@ class MyClass {
 
     // $TEST$ no error r"The template expressions? .* cannot be interpreted."
     @»PythonMacro«("myMethod2($this)")
-    fun myMethod2(`this`: Int)
+    fun myMethod2(^this: Int)
 
     // $TEST$ no error "The template expression '$this' cannot be interpreted."
     @»PythonMacro«("myMethod3($this)")
@@ -28,7 +28,7 @@ fun myFunction1(param: Int)
 
 // $TEST$ no error r"The template expressions? .* cannot be interpreted."
 @»PythonMacro«("myFunction2($this)")
-fun myFunction2(`this`: Int)
+fun myFunction2(^this: Int)
 
 // $TEST$ error "The template expression '$this' cannot be interpreted."
 @»PythonMacro«("myFunction3($this)")

packages/safe-ds-lang/tests/resources/validation/names/casing/annotations.sdsdev

@@ -3,7 +3,7 @@ package tests.validation.names.casing
 // $TEST$ no warning "Names of annotations should be UpperCamelCase."
 annotation »AnnotationUppercase1«
 // $TEST$ no warning "Names of annotations should be UpperCamelCase."
-annotation »`AnnotationUppercase2`«
+annotation »^AnnotationUppercase2«
 // $TEST$ warning "Names of annotations should be UpperCamelCase."
 annotation »annotationLowercase«
 // $TEST$ warning "Names of annotations should be UpperCamelCase."

packages/safe-ds-lang/tests/resources/validation/names/casing/attributes.sdsdev

@@ -6,7 +6,7 @@ class MyClass {
     // $TEST$ no warning "Names of attributes should be lowerCamelCase."
     attr »attributeLowercase1«: Int
     // $TEST$ no warning "Names of attributes should be lowerCamelCase."
-    attr »`attributeLowercase2`«: Int
+    attr »^attributeLowercase2«: Int
     // $TEST$ warning "Names of attributes should be lowerCamelCase."
     attr »_attributeUnderscore«: Int
     // $TEST$ warning "Names of attributes should be lowerCamelCase."

packages/safe-ds-lang/tests/resources/validation/names/casing/block lambda results.sdsdev

@@ -7,7 +7,7 @@ pipeline myPipeline1 {
         // $TEST$ no warning "Names of block lambda results should be lowerCamelCase."
         yield »lambdaResultLowercase1« = 1;
         // $TEST$ no warning "Names of block lambda results should be lowerCamelCase."
-        yield »`lambdaResultLowercase2`« = 1;
+        yield »^lambdaResultLowercase2« = 1;
         // $TEST$ warning "Names of block lambda results should be lowerCamelCase."
         yield »_lambdaResultUnderscore« = 1;
         // $TEST$ warning "Names of block lambda results should be lowerCamelCase."

packages/safe-ds-lang/tests/resources/validation/names/casing/classes.sdsdev

@@ -3,7 +3,7 @@ package tests.validation.names.casing
 // $TEST$ no warning "Names of classes should be UpperCamelCase."
 class »ClassUppercase1«
 // $TEST$ no warning "Names of classes should be UpperCamelCase."
-class »`ClassUppercase2`«
+class »^ClassUppercase2«
 // $TEST$ warning "Names of classes should be UpperCamelCase."
 class »classLowercase«
 // $TEST$ warning "Names of classes should be UpperCamelCase."

packages/safe-ds-lang/tests/resources/validation/names/casing/enum variants.sdsdev

@@ -4,7 +4,7 @@ enum MyEnum {
     // $TEST$ no warning "Names of enum variants should be UpperCamelCase."
     »EnumVariantUppercase1«
     // $TEST$ no warning "Names of enum variants should be UpperCamelCase."
-    »`EnumVariantUppercase2`«
+    »^EnumVariantUppercase2«
     // $TEST$ warning "Names of enum variants should be UpperCamelCase."
     »enumVariantLowercase«
     // $TEST$ warning "Names of enum variants should be UpperCamelCase."

packages/safe-ds-lang/tests/resources/validation/names/casing/enums.sdsdev

@@ -3,7 +3,7 @@ package tests.validation.names.casing
 // $TEST$ no warning "Names of enums should be UpperCamelCase."
 enum »EnumUppercase1«
 // $TEST$ no warning "Names of enums should be UpperCamelCase."
-enum »`EnumUppercase2`«
+enum »^EnumUppercase2«
 // $TEST$ warning "Names of enums should be UpperCamelCase."
 enum »enumLowercase«
 // $TEST$ warning "Names of enums should be UpperCamelCase."

packages/safe-ds-lang/tests/resources/validation/names/casing/functions.sdsdev

@@ -5,7 +5,7 @@ fun »FunctionUppercase«()
 // $TEST$ no warning "Names of functions should be lowerCamelCase."
 fun »functionLowercase1«()
 // $TEST$ no warning "Names of functions should be lowerCamelCase."
-fun »`functionLowercase2`«()
+fun »^functionLowercase2«()
 // $TEST$ warning "Names of functions should be lowerCamelCase."
 fun »_functionUnderscore«()
 // $TEST$ warning "Names of functions should be lowerCamelCase."

packages/safe-ds-lang/tests/resources/validation/names/casing/package name lowercase escaped.sdsdev

@@ -1,2 +1,2 @@
 // $TEST$ no warning "All segments of the qualified name of a package should be lowerCamelCase."
-package »tests.validation.declarations.`lowercase1`«
+package »tests.validation.declarations.^lowercase1«