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feat: type checker service (#722)
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Closes partially #666

### Summary of Changes

Implement & test type checker services. A later PR will use the service
to implement validation for types.
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@lars-reimann
lars-reimann committed Nov 4, 2023
1 parent 3e71cad commit daad5c4
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Showing 4 changed files with 695 additions and 75 deletions.
2 changes: 1 addition & 1 deletion packages/safe-ds-lang/src/language/helpers/nodeProperties.ts
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
import { AstNode, getContainerOfType, Stream, stream } from 'langium';
import {
isSdsAnnotation,
isSdsArgumentList,
Expand Down Expand Up @@ -57,7 +58,6 @@ import {
SdsTypeParameter,
SdsTypeParameterList,
} from '../generated/ast.js';
import { AstNode, getContainerOfType, Stream, stream } from 'langium';

// -------------------------------------------------------------------------------------------------
// Checks
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2 changes: 0 additions & 2 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 @@ -149,11 +149,9 @@ export class NamedTupleType<T extends SdsDeclaration> extends Type {
/**
* The length of this tuple.
*/
/* c8 ignore start */
get length(): number {
return this.entries.length;
}
/* c8 ignore stop */

/**
* Returns the type of the entry at the given index. If the index is out of bounds, returns `undefined`.
Expand Down
161 changes: 89 additions & 72 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
@@ -1,4 +1,5 @@
import { getContainerOfType } from 'langium';
import type { SafeDsClasses } from '../builtins/safe-ds-classes.js';
import { isSdsEnum, SdsDeclaration } from '../generated/ast.js';
import {
BooleanConstant,
Expand All @@ -19,16 +20,18 @@ import {
StaticType,
Type,
UnionType,
UnknownType,
} from './model.js';
import { SafeDsClassHierarchy } from './safe-ds-class-hierarchy.js';
import { SafeDsCoreTypes } from './safe-ds-core-types.js';

/* c8 ignore start */
export class SafeDsTypeChecker {
private readonly builtinClasses: SafeDsClasses;
private readonly classHierarchy: SafeDsClassHierarchy;
private readonly coreTypes: SafeDsCoreTypes;

constructor(services: SafeDsServices) {
this.builtinClasses = services.builtins.Classes;
this.classHierarchy = services.types.ClassHierarchy;
this.coreTypes = services.types.CoreTypes;
}
Expand All @@ -37,6 +40,12 @@ export class SafeDsTypeChecker {
* Checks whether {@link type} is assignable {@link other}.
*/
isAssignableTo(type: Type, other: Type): boolean {
if (type === UnknownType || other === UnknownType) {
return false;
} else if (other instanceof UnionType) {
return other.possibleTypes.some((it) => this.isAssignableTo(type, it));
}

if (type instanceof CallableType) {
return this.callableTypeIsAssignableTo(type, other);
} else if (type instanceof ClassType) {
Expand All @@ -53,48 +62,66 @@ export class SafeDsTypeChecker {
return this.staticTypeIsAssignableTo(type, other);
} else if (type instanceof UnionType) {
return this.unionTypeIsAssignableTo(type, other);
} else {
return false;
}
} /* c8 ignore start */ else {
throw new Error(`Unexpected type: ${type.constructor.name}`);
} /* c8 ignore stop */
}

private callableTypeIsAssignableTo(type: CallableType, other: Type): boolean {
// return when (val unwrappedOther = unwrapVariadicType(other)) {
// is CallableType -> {
// // TODO: We need to compare names of parameters & results and can allow additional optional parameters
//
// // Sizes must match (too strict requirement -> should be loosened later)
// if (this.parameters.size != unwrappedOther.parameters.size || this.results.size != this.results.size) {
// return false
// }
//
// // Actual parameters must be supertypes of expected parameters (contravariance)
// this.parameters.zip(unwrappedOther.parameters).forEach { (thisParameter, otherParameter) ->
// if (!otherParameter.isSubstitutableFor(thisParameter)) {
// return false
// }
// }
//
// // Expected results must be subtypes of expected results (covariance)
// this.results.zip(unwrappedOther.results).forEach { (thisResult, otherResult) ->
// if (!thisResult.isSubstitutableFor(otherResult)) {
// return false
// }
// }
//
// true
// }
// is ClassType -> {
// unwrappedOther.sdsClass.qualifiedNameOrNull() == StdlibClasses.Any
// }
// is UnionType -> {
// unwrappedOther.possibleTypes.any { this.isSubstitutableFor(it) }
// }
// else -> false
// }
// }
if (other instanceof ClassType) {
return other.declaration === this.builtinClasses.Any;
} else if (other instanceof CallableType) {
// Must accept at least as many parameters and produce at least as many results
if (type.inputType.length < other.inputType.length || type.outputType.length < other.outputType.length) {
return false;
}

return type.equals(other);
// Check expected parameters
for (let i = 0; i < other.inputType.length; i++) {
const typeEntry = type.inputType.entries[i];
const otherEntry = other.inputType.entries[i];

// Names must match
if (typeEntry.name !== otherEntry.name) {
return false;
}

// Types must be contravariant
if (!this.isAssignableTo(otherEntry.type, typeEntry.type)) {
return false;
}
}

// Additional parameters must be optional
for (let i = other.inputType.length; i < type.inputType.length; i++) {
const typeEntry = type.inputType.entries[i];
if (!typeEntry.declaration?.defaultValue) {
return false;
}
}

// Check expected results
for (let i = 0; i < other.outputType.length; i++) {
const typeEntry = type.outputType.entries[i];
const otherEntry = other.outputType.entries[i];

// Names must match
if (typeEntry.name !== otherEntry.name) {
return false;
}

// Types must be covariant
if (!this.isAssignableTo(typeEntry.type, otherEntry.type)) {
return false;
}
}

// Additional results are OK

return true;
} else {
return false;
}
}

private classTypeIsAssignableTo(type: ClassType, other: Type): boolean {
Expand All @@ -104,8 +131,6 @@ export class SafeDsTypeChecker {

if (other instanceof ClassType) {
return this.classHierarchy.isEqualToOrSubclassOf(type.declaration, other.declaration);
} else if (other instanceof UnionType) {
return other.possibleTypes.some((it) => this.isAssignableTo(type, it));
} else {
return false;
}
Expand All @@ -116,45 +141,30 @@ export class SafeDsTypeChecker {
return false;
}

if (other instanceof EnumType) {
if (other instanceof ClassType) {
return other.declaration === this.builtinClasses.Any;
} else if (other instanceof EnumType) {
return type.declaration === other.declaration;
} else {
return false;
}

// return when (val unwrappedOther = unwrapVariadicType(other)) {
// is ClassType -> {
// (!this.isNullable || unwrappedOther.isNullable) &&
// unwrappedOther.sdsClass.qualifiedNameOrNull() == StdlibClasses.Any
// }
// is UnionType -> {
// unwrappedOther.possibleTypes.any { this.isSubstitutableFor(it) }
// }
// else -> false
// }

return type.equals(other);
}

private enumVariantTypeIsAssignableTo(type: EnumVariantType, other: Type): boolean {
if (type.isNullable && !other.isNullable) {
return false;
}

if (other instanceof EnumType) {
if (other instanceof ClassType) {
return other.declaration === this.builtinClasses.Any;
} else if (other instanceof EnumType) {
const containingEnum = getContainerOfType(type.declaration, isSdsEnum);
return containingEnum === other.declaration;
} else if (other instanceof EnumVariantType) {
return type.declaration === other.declaration;
} else {
return false;
}
// return when (val unwrappedOther = unwrapVariadicType(other)) {
// is ClassType -> {
// (!this.isNullable || unwrappedOther.isNullable) &&
// unwrappedOther.sdsClass.qualifiedNameOrNull() == StdlibClasses.Any
// }
// is UnionType -> unwrappedOther.possibleTypes.any { this.isSubstitutableFor(it) }
// else -> false
// }

return type.equals(other);
}

private literalTypeIsAssignableTo(type: LiteralType, other: Type): boolean {
Expand All @@ -173,7 +183,6 @@ export class SafeDsTypeChecker {
other.constants.some((otherConstant) => constant.equals(otherConstant)),
);
} else {
// TODO: union type
return false;
}
}
Expand All @@ -197,18 +206,26 @@ export class SafeDsTypeChecker {
return this.isAssignableTo(classType, other);
}

/* c8 ignore start */
private namedTupleTypeIsAssignableTo(type: NamedTupleType<SdsDeclaration>, other: Type): boolean {
return type.equals(other);
if (other instanceof NamedTupleType) {
return (
type.length === other.length &&
type.entries.every((typeEntry, index) => {
const otherEntry = other.entries[index];
// We deliberately ignore the declarations here
return typeEntry.name === otherEntry.name && this.isAssignableTo(typeEntry.type, otherEntry.type);
})
);
} else {
return false;
}
}

private staticTypeIsAssignableTo(type: Type, other: Type): boolean {
return type.equals(other);
}

private unionTypeIsAssignableTo(type: UnionType, other: Type): boolean {
// return this.possibleTypes.all { it.isSubstitutableFor(other) }
return type.equals(other);
return type.possibleTypes.every((it) => this.isAssignableTo(it, other));
}
}
/* c8 ignore stop */
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