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feat: Constructor generic type inference #2894

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feat: Constructor generic type inference #2894

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46c9ead
Refactor to extract existing inference logic
mattjohnsonpint Jan 12, 2025
df03df9
Infer type arguments for constructor calls
mattjohnsonpint Jan 12, 2025
983c40f
Update tests
mattjohnsonpint Jan 12, 2025
815721e
Fix bootstrap errors
mattjohnsonpint Jan 12, 2025
3b03351
Handle constructor on base class
mattjohnsonpint Jan 12, 2025
48758f5
oops - put tests back
mattjohnsonpint Jan 12, 2025
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271 changes: 169 additions & 102 deletions src/resolver.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -731,110 +731,158 @@ export class Resolver extends DiagnosticEmitter {

// infer generic call if type arguments have been omitted
if (prototype.is(CommonFlags.Generic)) {
let contextualTypeArguments = cloneMap(ctxFlow.contextualTypeArguments);
let resolvedTypeArguments = this.inferGenericTypeArguments(
node,
prototype,
prototype.typeParameterNodes,
ctxFlow,
reportMode,
);

return this.resolveFunction(
prototype,
resolvedTypeArguments,
cloneMap(ctxFlow.contextualTypeArguments),
reportMode
);
}

// fill up contextual types with auto for each generic component
let typeParameterNodes = assert(prototype.typeParameterNodes);
let numTypeParameters = typeParameterNodes.length;
let typeParameterNames = new Set<string>();
for (let i = 0; i < numTypeParameters; ++i) {
let name = typeParameterNodes[i].name.text;
contextualTypeArguments.set(name, Type.auto);
typeParameterNames.add(name);
}

let parameterNodes = prototype.functionTypeNode.parameters;
let numParameters = parameterNodes.length;
let argumentNodes = node.args;
let numArguments = argumentNodes.length;

// infer types with generic components while updating contextual types
for (let i = 0; i < numParameters; ++i) {
let argumentExpression = i < numArguments
? argumentNodes[i]
: parameterNodes[i].initializer;
if (!argumentExpression) {
// optional but not have initializer should be handled in the other place
if (parameterNodes[i].parameterKind == ParameterKind.Optional) {
continue;
}
// missing initializer -> too few arguments
if (reportMode == ReportMode.Report) {
this.error(
DiagnosticCode.Expected_0_arguments_but_got_1,
node.range, numParameters.toString(), numArguments.toString()
);
}
return null;
// otherwise resolve the non-generic call as usual
return this.resolveFunction(prototype, null, new Map(), reportMode);
}

private inferGenericTypeArguments(
node: Expression,
prototype: FunctionPrototype,
typeParameterNodes: TypeParameterNode[] | null,
ctxFlow: Flow,
reportMode: ReportMode = ReportMode.Report,
): Type[] | null {

if (!typeParameterNodes) {
return null;
}

let contextualTypeArguments = cloneMap(ctxFlow.contextualTypeArguments);

// fill up contextual types with auto for each generic component
let numTypeParameters = typeParameterNodes.length;
let typeParameterNames = new Set<string>();
for (let i = 0; i < numTypeParameters; ++i) {
let name = typeParameterNodes[i].name.text;
contextualTypeArguments.set(name, Type.auto);
typeParameterNames.add(name);
}

let parameterNodes = prototype.functionTypeNode.parameters;
let numParameters = parameterNodes.length;

let argumentNodes: Expression[];
switch (node.kind) {
case NodeKind.Call:
argumentNodes = (<CallExpression>node).args;
break;
case NodeKind.New:
argumentNodes = (<NewExpression>node).args;
break;
default:
assert(false);
return null;
}

let numArguments = argumentNodes.length;

// infer types with generic components while updating contextual types
for (let i = 0; i < numParameters; ++i) {
let argumentExpression = i < numArguments
? argumentNodes[i]
: parameterNodes[i].initializer;
if (!argumentExpression) {
// optional but not have initializer should be handled in the other place
if (parameterNodes[i].parameterKind == ParameterKind.Optional) {
continue;
}
// missing initializer -> too few arguments
if (reportMode == ReportMode.Report) {
this.error(
DiagnosticCode.Expected_0_arguments_but_got_1,
node.range, numParameters.toString(), numArguments.toString()
);
}
let typeNode = parameterNodes[i].type;
if (typeNode.hasGenericComponent(typeParameterNodes)) {
let type = this.resolveExpression(argumentExpression, ctxFlow, Type.auto, ReportMode.Swallow);
if (type) {
this.propagateInferredGenericTypes(
typeNode,
type,
prototype,
contextualTypeArguments,
typeParameterNames
);
}
return null;
}
let typeNode = parameterNodes[i].type;
if (typeNode.hasGenericComponent(typeParameterNodes)) {
let type = this.resolveExpression(argumentExpression, ctxFlow, Type.auto, ReportMode.Swallow);
if (type) {
this.propagateInferredGenericTypes(
typeNode,
type,
prototype,
contextualTypeArguments,
typeParameterNames
);
}
}
}

// apply concrete types to the generic function signature
let resolvedTypeArguments = new Array<Type>(numTypeParameters);
for (let i = 0; i < numTypeParameters; ++i) {
let typeParameterNode = typeParameterNodes[i];
let name = typeParameterNode.name.text;
if (contextualTypeArguments.has(name)) {
let inferredType = assert(contextualTypeArguments.get(name));
if (inferredType != Type.auto) {
resolvedTypeArguments[i] = inferredType;
continue;
}
let defaultType = typeParameterNode.defaultType;
if (defaultType) {
// Default parameters are resolved in context of the called function, not the calling function
let parent = prototype.parent;
let defaultTypeContextualTypeArguments: Map<string, Type> | null = null;
if (parent.kind == ElementKind.Class) {
defaultTypeContextualTypeArguments = (<Class>parent).contextualTypeArguments;
} else if (parent.kind == ElementKind.Function) {
defaultTypeContextualTypeArguments = (<Function>parent).contextualTypeArguments;
}
let resolvedDefaultType = this.resolveType(
defaultType,
null,
prototype,
defaultTypeContextualTypeArguments,
reportMode
);
if (!resolvedDefaultType) return null;
resolvedTypeArguments[i] = resolvedDefaultType;
continue;
// apply concrete types to the generic function signature
let resolvedTypeArguments = new Array<Type>(numTypeParameters);
for (let i = 0; i < numTypeParameters; ++i) {
let typeParameterNode = typeParameterNodes[i];
let name = typeParameterNode.name.text;
if (contextualTypeArguments.has(name)) {
let inferredType = assert(contextualTypeArguments.get(name));
if (inferredType != Type.auto) {
resolvedTypeArguments[i] = inferredType;
continue;
}
let defaultType = typeParameterNode.defaultType;
if (defaultType) {
// Default parameters are resolved in context of the called function, not the calling function
let parent = prototype.parent;
let defaultTypeContextualTypeArguments: Map<string, Type> | null = null;
if (parent.kind == ElementKind.Class) {
defaultTypeContextualTypeArguments = (<Class>parent).contextualTypeArguments;
} else if (parent.kind == ElementKind.Function) {
defaultTypeContextualTypeArguments = (<Function>parent).contextualTypeArguments;
}
}
// unused template, e.g. `function test<T>(): void {...}` called as `test()`
// invalid because the type is effectively unknown inside the function body
if (reportMode == ReportMode.Report) {
this.error(
DiagnosticCode.Type_argument_expected,
node.expression.range.atEnd
let resolvedDefaultType = this.resolveType(
defaultType,
null,
prototype,
defaultTypeContextualTypeArguments,
reportMode
);
if (!resolvedDefaultType) return null;
resolvedTypeArguments[i] = resolvedDefaultType;
continue;
}
return null;
}
return this.resolveFunction(
prototype,
resolvedTypeArguments,
cloneMap(ctxFlow.contextualTypeArguments),
reportMode
);
// unused template, e.g. `function test<T>(): void {...}` called as `test()`
// invalid because the type is effectively unknown inside the function body
if (reportMode == ReportMode.Report) {
let range: Range;
switch (node.kind) {
case NodeKind.Call:
range = (<CallExpression>node).expression.range;
break;
case NodeKind.New:
range = (<NewExpression>node).typeName.range;
break;
default:
assert(false);
return null;
}
this.error(
DiagnosticCode.Type_argument_expected,
range.atEnd
);
}
return null;
}

// otherwise resolve the non-generic call as usual
return this.resolveFunction(prototype, null, new Map(), reportMode);
return resolvedTypeArguments;
}

/** Updates contextual types with a possibly encapsulated inferred type. */
Expand Down Expand Up @@ -3644,15 +3692,34 @@ export class Resolver extends DiagnosticEmitter {

// Resolve type arguments if generic
if (prototype.is(CommonFlags.Generic)) {
resolvedTypeArguments = this.resolveTypeArguments( // reports
assert(prototype.typeParameterNodes), // must be present if generic
typeArgumentNodes,
flow,
ctxElement,
ctxTypes, // update
reportNode,
reportMode
);

// find the constructor prototype, which may be on a base class
let constructorPrototype: FunctionPrototype | null = null;
for (let p: ClassPrototype | null = prototype; p && !constructorPrototype; p = p.basePrototype) {
constructorPrototype = p.constructorPrototype;
}

// if no type arguments are provided, try to infer them from the constructor call
if (!typeArgumentNodes && constructorPrototype && flow && ctxTypes.size == 0) {
resolvedTypeArguments = this.inferGenericTypeArguments(
reportNode as NewExpression,
constructorPrototype,
prototype.typeParameterNodes,
flow,
);
} else {
// resolve them from the provided type argument nodes
resolvedTypeArguments = this.resolveTypeArguments( // reports
assert(prototype.typeParameterNodes), // must be present if generic
typeArgumentNodes,
flow,
ctxElement,
ctxTypes, // update
reportNode,
reportMode
);
}

if (!resolvedTypeArguments) return null;

// Otherwise make sure that no type arguments have been specified
Expand Down
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