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refactor: rename "type parameter type" to "type variable" (#1051)
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### Summary of Changes

Rename the type "type parameter type" to "type variable". This is
shorter, less cumbersome, and better highlights that this type can be
substituted by another type.
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@lars-reimann
lars-reimann authored Apr 15, 2024
1 parent 46145dd commit f6330a1
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Showing 18 changed files with 81 additions and 87 deletions.
4 changes: 2 additions & 2 deletions packages/safe-ds-lang/src/language/generation/safe-ds-markdown-generator.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ import { SafeDsDocumentationProvider } from '../documentation/safe-ds-documentat
import { SafeDsAnnotations } from '../builtins/safe-ds-annotations.js';
import { isEmpty } from '../../helpers/collections.js';
import { SafeDsTypeComputer } from '../typing/safe-ds-type-computer.js';
import { NamedType, Type, TypeParameterType } from '../typing/model.js';
import { NamedType, Type, TypeVariable } from '../typing/model.js';
import path from 'path';
import { addLinePrefix, removeLinePrefix } from '../../helpers/strings.js';
import { expandToStringLF } from 'langium/generate';
Expand Down Expand Up @@ -544,7 +544,7 @@ export class SafeDsMarkdownGenerator {
}

private renderType(type: Type, knownPaths: Set<string>): string {
if (type instanceof NamedType && !(type instanceof TypeParameterType)) {
if (type instanceof NamedType && !(type instanceof TypeVariable)) {
const realPath = AstUtils.getDocument(type.declaration).uri.fsPath;
// When generating documentation for the standard library declarations in the `src` folder, references are
// resolved to the `lib` folder. To still create links, we also check this augmented path.
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4 changes: 2 additions & 2 deletions packages/safe-ds-lang/src/language/scoping/safe-ds-scope-provider.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,7 @@ import {
} from '../helpers/nodeProperties.js';
import { SafeDsNodeMapper } from '../helpers/safe-ds-node-mapper.js';
import { SafeDsServices } from '../safe-ds-module.js';
import { ClassType, EnumVariantType, LiteralType, TypeParameterType } from '../typing/model.js';
import { ClassType, EnumVariantType, LiteralType, TypeVariable } from '../typing/model.js';
import type { SafeDsClassHierarchy } from '../typing/safe-ds-class-hierarchy.js';
import { SafeDsTypeComputer } from '../typing/safe-ds-type-computer.js';
import { SafeDsPackageManager } from '../workspace/safe-ds-package-manager.js';
Expand Down Expand Up @@ -244,7 +244,7 @@ export class SafeDsScopeProvider extends DefaultScopeProvider {
let receiverType = this.typeComputer.computeType(node.receiver);
if (receiverType instanceof LiteralType) {
receiverType = this.typeComputer.computeClassTypeForLiteralType(receiverType);
} else if (receiverType instanceof TypeParameterType) {
} else if (receiverType instanceof TypeVariable) {
receiverType = this.typeComputer.computeUpperBound(receiverType);
}

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8 changes: 4 additions & 4 deletions packages/safe-ds-lang/src/language/typing/model.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -532,7 +532,7 @@ export class EnumVariantType extends NamedType<SdsEnumVariant> {
}
}

export class TypeParameterType extends NamedType<SdsTypeParameter> {
export class TypeVariable extends NamedType<SdsTypeParameter> {
override readonly isFullySubstituted = false;

constructor(
Expand All @@ -545,7 +545,7 @@ export class TypeParameterType extends NamedType<SdsTypeParameter> {
override equals(other: unknown): boolean {
if (other === this) {
return true;
} else if (!(other instanceof TypeParameterType)) {
} else if (!(other instanceof TypeVariable)) {
return false;
}

Expand All @@ -564,12 +564,12 @@ export class TypeParameterType extends NamedType<SdsTypeParameter> {
}
}

override withExplicitNullability(isExplicitlyNullable: boolean): TypeParameterType {
override withExplicitNullability(isExplicitlyNullable: boolean): TypeVariable {
if (this.isExplicitlyNullable === isExplicitlyNullable) {
return this;
}

return new TypeParameterType(this.declaration, isExplicitlyNullable);
return new TypeVariable(this.declaration, isExplicitlyNullable);
}
}

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24 changes: 12 additions & 12 deletions packages/safe-ds-lang/src/language/typing/safe-ds-type-checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ import {
NamedTupleType,
StaticType,
Type,
TypeParameterType,
TypeVariable,
UnionType,
UnknownType,
} from './model.js';
Expand Down Expand Up @@ -58,13 +58,13 @@ export class SafeDsTypeChecker {
}

// Handle type parameter types
if (other instanceof TypeParameterType) {
if (other instanceof TypeVariable) {
if (type.isExplicitlyNullable && !other.isExplicitlyNullable) {
return false;
}

// `T` can always be assigned to `T` or some type parameter it is bounded by
if (type instanceof TypeParameterType && this.typeParameterIsBoundedByTypeParameter(type, other)) {
if (type instanceof TypeVariable && this.typeVariableIsBoundedByTypeVariable(type, other)) {
return true;
}

Expand Down Expand Up @@ -94,22 +94,22 @@ export class SafeDsTypeChecker {
return this.namedTupleTypeIsSubtypeOf(type, other, options);
} else if (type instanceof StaticType) {
return this.staticTypeIsSubtypeOf(type, other, options);
} else if (type instanceof TypeParameterType) {
return this.typeParameterTypeIsSubtypeOf(type, other, options);
} else if (type instanceof TypeVariable) {
return this.typeVariableIsSubtypeOf(type, other, options);
} /* c8 ignore start */ else {
throw new Error(`Unexpected type: ${type.constructor.name}`);
} /* c8 ignore stop */
};

private typeParameterIsBoundedByTypeParameter(type: TypeParameterType, other: TypeParameterType): boolean {
private typeVariableIsBoundedByTypeVariable(type: TypeVariable, other: TypeVariable): boolean {
let current: Type = type;

while (current instanceof TypeParameterType) {
while (current instanceof TypeVariable) {
if (current.declaration === other.declaration) {
return true;
}

current = this.typeComputer().computeUpperBound(current, { stopAtTypeParameterType: true });
current = this.typeComputer().computeUpperBound(current, { stopAtTypeVariable: true });
}

return false;
Expand Down Expand Up @@ -313,7 +313,7 @@ export class SafeDsTypeChecker {
}
}

private typeParameterTypeIsSubtypeOf(type: TypeParameterType, other: Type, options: TypeCheckOptions): boolean {
private typeVariableIsSubtypeOf(type: TypeVariable, other: Type, options: TypeCheckOptions): boolean {
const upperBound = this.typeComputer().computeUpperBound(type);
return this.isSubtypeOf(upperBound, other, options);
}
Expand Down Expand Up @@ -358,7 +358,7 @@ export class SafeDsTypeChecker {
canBeNull = (type: Type): boolean => {
if (type.isExplicitlyNullable) {
return true;
} else if (type instanceof TypeParameterType) {
} else if (type instanceof TypeVariable) {
const upperBound = this.typeComputer().computeUpperBound(type);
return upperBound.isExplicitlyNullable;
} else {
Expand Down Expand Up @@ -392,7 +392,7 @@ export class SafeDsTypeChecker {
/**
* Checks whether {@link type} is some kind of list (with any element type).
*/
isList(type: Type): type is ClassType | TypeParameterType {
isList(type: Type): type is ClassType | TypeVariable {
const listOrNull = this.coreTypes.List(UnknownType).withExplicitNullability(true);

return (
Expand All @@ -407,7 +407,7 @@ export class SafeDsTypeChecker {
/**
* Checks whether {@link type} is some kind of map (with any key/value types).
*/
isMap(type: Type): type is ClassType | TypeParameterType {
isMap(type: Type): type is ClassType | TypeVariable {
const mapOrNull = this.coreTypes.Map(UnknownType, UnknownType).withExplicitNullability(true);

return (
Expand Down
46 changes: 23 additions & 23 deletions packages/safe-ds-lang/src/language/typing/safe-ds-type-computer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ import {
StaticType,
Type,
TypeParameterSubstitutions,
TypeParameterType,
TypeVariable,
UnionType,
UnknownType,
} from './model.js';
Expand Down Expand Up @@ -249,7 +249,7 @@ export class SafeDsTypeComputer {
} else if (isSdsSegment(node)) {
return this.computeTypeOfCallableWithManifestTypes(node, state);
} else if (isSdsTypeParameter(node)) {
return this.factory.createTypeParameterType(node, false);
return this.factory.createTypeVariable(node, false);
} /* c8 ignore start */ else {
return UnknownType;
} /* c8 ignore stop */
Expand Down Expand Up @@ -535,7 +535,7 @@ export class SafeDsTypeComputer {

private computeTypeOfIndexedAccess(node: SdsIndexedAccess, state: ComputeTypeState): Type {
const receiverType = this.computeTypeWithRecursionCheck(node.receiver, state);
if (!(receiverType instanceof ClassType) && !(receiverType instanceof TypeParameterType)) {
if (!(receiverType instanceof ClassType) && !(receiverType instanceof TypeVariable)) {
return UnknownType;
}

Expand Down Expand Up @@ -754,19 +754,19 @@ export class SafeDsTypeComputer {
* invalid upper bounds are specified, but are invalid (e.g. because of an unresolved reference or a cycle),
* `unknown` is returned. The result is simplified as much as possible.
*/
computeUpperBound(nodeOrType: SdsTypeParameter | TypeParameterType, options: ComputeUpperBoundOptions = {}): Type {
let type: TypeParameterType;
if (nodeOrType instanceof TypeParameterType) {
computeUpperBound(nodeOrType: SdsTypeParameter | TypeVariable, options: ComputeUpperBoundOptions = {}): Type {
let type: TypeVariable;
if (nodeOrType instanceof TypeVariable) {
type = nodeOrType;
} else {
type = this.computeType(nodeOrType) as TypeParameterType;
type = this.computeType(nodeOrType) as TypeVariable;
}

const result = this.doComputeUpperBound(type, options);
return result.withExplicitNullability(result.isExplicitlyNullable || type.isExplicitlyNullable);
}

private doComputeUpperBound(type: TypeParameterType, options: ComputeUpperBoundOptions): Type {
private doComputeUpperBound(type: TypeVariable, options: ComputeUpperBoundOptions): Type {
const upperBound = type.declaration.upperBound;
if (!upperBound) {
return this.coreTypes.AnyOrNull;
Expand All @@ -775,7 +775,7 @@ export class SafeDsTypeComputer {
const boundType = this.computeType(upperBound);
if (!(boundType instanceof NamedType)) {
return UnknownType;
} else if (options.stopAtTypeParameterType || !(boundType instanceof TypeParameterType)) {
} else if (options.stopAtTypeVariable || !(boundType instanceof TypeVariable)) {
return boundType;
} else {
return this.doComputeUpperBound(boundType, options);
Expand Down Expand Up @@ -937,7 +937,7 @@ export class SafeDsTypeComputer {

// Clamp to upper bound
const upperBound = this.computeUpperBound(typeParameter, {
stopAtTypeParameterType: true,
stopAtTypeVariable: true,
}).substituteTypeParameters(state.substitutions);

if (!this.typeChecker.isSubtypeOf(newSubstitution, upperBound)) {
Expand All @@ -956,7 +956,7 @@ export class SafeDsTypeComputer {
currentVariance: Variance,
state: ComputeSubstitutionsForParametersState,
) {
if (argumentType instanceof TypeParameterType && state.substitutions.has(argumentType.declaration)) {
if (argumentType instanceof TypeVariable && state.substitutions.has(argumentType.declaration)) {
// Can happen for lambdas without manifest parameter types. We gain no information here.
return;
} else if (parameterType instanceof CallableType && argumentType instanceof CallableType) {
Expand Down Expand Up @@ -1029,7 +1029,7 @@ export class SafeDsTypeComputer {
);
}
}
} else if (parameterType instanceof TypeParameterType) {
} else if (parameterType instanceof TypeVariable) {
const currentSubstitution = state.substitutions.get(parameterType.declaration);
const remainingVariance = state.remainingVariances.get(parameterType.declaration);
if (!currentSubstitution) {
Expand Down Expand Up @@ -1076,8 +1076,8 @@ export class SafeDsTypeComputer {
return simplifiedTypes[0]!;
}

// Replace type parameter types by their upper bound
const replacedTypes = this.replaceTypeParameterTypesWithUpperBound(simplifiedTypes);
// Replace type variables by their upper bound
const replacedTypes = this.replaceVariablesWithUpperBound(simplifiedTypes);

// Partition types by their kind
const partitionedTypes = this.partitionTypesLCS(replacedTypes);
Expand Down Expand Up @@ -1130,9 +1130,9 @@ export class SafeDsTypeComputer {
}
}

private replaceTypeParameterTypesWithUpperBound(simplifiedTypes: Type[]) {
private replaceVariablesWithUpperBound(simplifiedTypes: Type[]) {
return simplifiedTypes.map((it) => {
if (it instanceof TypeParameterType) {
if (it instanceof TypeVariable) {
return this.computeUpperBound(it);
} else {
return it;
Expand Down Expand Up @@ -1454,7 +1454,7 @@ export class SafeDsTypeComputer {
const substitutions: TypeParameterSubstitutions = new Map();

for (const typeParameter of typeParameters) {
substitutions.set(typeParameter, this.factory.createTypeParameterType(typeParameter, false));
substitutions.set(typeParameter, this.factory.createTypeVariable(typeParameter, false));
}

return this.factory.createClassType(declaration, substitutions, type.isExplicitlyNullable);
Expand All @@ -1474,7 +1474,7 @@ export class SafeDsTypeComputer {
// See where the type parameters ended up in the computed super type
const invertedTypeParameterMap = new Map<SdsTypeParameter, SdsTypeParameter>();
for (const [key, value] of superType.substitutions) {
if (value instanceof TypeParameterType) {
if (value instanceof TypeVariable) {
invertedTypeParameterMap.set(value.declaration, key);
}
}
Expand Down Expand Up @@ -1557,7 +1557,7 @@ export class SafeDsTypeComputer {
* parameters on parent types get substituted.
*/
computeMatchingSupertype(
type: ClassType | TypeParameterType | undefined,
type: ClassType | TypeVariable | undefined,
target: SdsClass | undefined,
): ClassType | undefined {
// Handle undefined
Expand All @@ -1566,7 +1566,7 @@ export class SafeDsTypeComputer {
}

// Handle type parameter types
if (type instanceof TypeParameterType) {
if (type instanceof TypeVariable) {
const upperBound = this.computeUpperBound(type);
if (upperBound instanceof ClassType) {
return this.computeMatchingSupertype(upperBound, target);
Expand Down Expand Up @@ -1672,10 +1672,10 @@ export class SafeDsTypeComputer {
*/
interface ComputeUpperBoundOptions {
/**
* If `true`, the computation stops at type parameter types and returns them as is. Otherwise, it finds the bounds
* for the type parameter types recursively.
* If `true`, the computation stops at type variables and returns them as is. Otherwise, it finds the bounds for the
* type variable recursively.
*/
stopAtTypeParameterType?: boolean;
stopAtTypeVariable?: boolean;
}

interface ComputeTypeState {
Expand Down
6 changes: 3 additions & 3 deletions packages/safe-ds-lang/src/language/typing/safe-ds-type-factory.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ import {
StaticType,
Type,
TypeParameterSubstitutions,
TypeParameterType,
TypeVariable,
UnionType,
} from './model.js';
import { Constant } from '../partialEvaluation/model.js';
Expand Down Expand Up @@ -66,8 +66,8 @@ export class SafeDsTypeFactory {
return new StaticType(this.services, instanceType);
}

createTypeParameterType(declaration: SdsTypeParameter, isExplicitlyNullable: boolean): TypeParameterType {
return new TypeParameterType(declaration, isExplicitlyNullable);
createTypeVariable(declaration: SdsTypeParameter, isExplicitlyNullable: boolean): TypeVariable {
return new TypeVariable(declaration, isExplicitlyNullable);
}

createUnionType(...types: Type[]): UnionType {
Expand Down
8 changes: 4 additions & 4 deletions packages/safe-ds-lang/src/language/validation/types.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ import {
} from '../generated/ast.js';
import { getArguments, getTypeArguments, getTypeParameters, TypeParameter } from '../helpers/nodeProperties.js';
import { SafeDsServices } from '../safe-ds-module.js';
import { ClassType, NamedTupleType, TypeParameterType, UnknownType } from '../typing/model.js';
import { ClassType, NamedTupleType, TypeVariable, UnknownType } from '../typing/model.js';

export const CODE_TYPE_CALLABLE_RECEIVER = 'type/callable-receiver';
export const CODE_TYPE_MISMATCH = 'type/mismatch';
Expand Down Expand Up @@ -135,7 +135,7 @@ export const indexedAccessIndexMustHaveCorrectType = (services: SafeDsServices)
code: CODE_TYPE_MISMATCH,
});
}
} else if (receiverType instanceof ClassType || receiverType instanceof TypeParameterType) {
} else if (receiverType instanceof ClassType || receiverType instanceof TypeVariable) {
const mapType = typeComputer.computeMatchingSupertype(receiverType, coreClasses.Map);
if (mapType) {
const keyType = mapType.getTypeParameterTypeByIndex(0);
Expand Down Expand Up @@ -293,7 +293,7 @@ export const namedTypeTypeArgumentsMustMatchBounds = (services: SafeDsServices)
}

const upperBound = typeComputer
.computeUpperBound(typeParameter, { stopAtTypeParameterType: true })
.computeUpperBound(typeParameter, { stopAtTypeVariable: true })
.substituteTypeParameters(type.substitutions);

if (!typeChecker.isSubtypeOf(typeArgumentType, upperBound)) {
Expand Down Expand Up @@ -400,7 +400,7 @@ export const typeParameterDefaultValueMustMatchUpperBound = (services: SafeDsSer
}

const defaultValueType = typeComputer.computeType(node.defaultValue);
const upperBoundType = typeComputer.computeUpperBound(node, { stopAtTypeParameterType: true });
const upperBoundType = typeComputer.computeUpperBound(node, { stopAtTypeVariable: true });

if (!typeChecker.isSubtypeOf(defaultValueType, upperBoundType)) {
accept('error', `Expected type '${upperBoundType}' but got '${defaultValueType}'.`, {
Expand Down
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