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Merged
merged 6 commits into from
Oct 18, 2016
Merged

Contextual typing of partially annotated signatures #11673

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8094b2c
Improve contextual typing of partially annotated signatures
ahejlsberg Oct 17, 2016
808db07
Accept new baselines
ahejlsberg Oct 17, 2016
6425f0c
Fix lint error
ahejlsberg Oct 17, 2016
df58df1
Add partially annotated function tests
HerringtonDarkholme Oct 17, 2016
8aa56c1
Add fourslash test for contextually-typed `this`
sandersn Oct 17, 2016
af52b63
Address CR feedback
ahejlsberg Oct 17, 2016
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Improve contextual typing of partially annotated signatures
  • Loading branch information
@ahejlsberg
ahejlsberg committed Oct 17, 2016
commit 8094b2c5def5ed39e5a9ddc18bfd09bab731aa11
66 changes: 47 additions & 19 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3144,8 +3144,7 @@ namespace ts {
// Use contextual parameter type if one is available
let type: Type;
if (declaration.symbol.name === "this") {
const thisParameter = getContextualThisParameter(func);
type = thisParameter ? getTypeOfSymbol(thisParameter) : undefined;
type = getContextualThisParameterType(func);
}
else {
type = getContextuallyTypedParameterType(<ParameterDeclaration>declaration);
Expand Down Expand Up @@ -4789,9 +4788,6 @@ namespace ts {
if (isJSConstructSignature) {
minArgumentCount--;
}
if (!thisParameter && isObjectLiteralMethod(declaration)) {
thisParameter = getContextualThisParameter(declaration);
}

const classType = declaration.kind === SyntaxKind.Constructor ?
getDeclaredTypeOfClassOrInterface(getMergedSymbol((<ClassDeclaration>declaration.parent).symbol))
Expand Down Expand Up @@ -6101,9 +6097,24 @@ namespace ts {
}

function isContextSensitiveFunctionLikeDeclaration(node: FunctionLikeDeclaration) {
const areAllParametersUntyped = !forEach(node.parameters, p => p.type);
const isNullaryArrow = node.kind === SyntaxKind.ArrowFunction && !node.parameters.length;
return !node.typeParameters && areAllParametersUntyped && !isNullaryArrow;
// Functions with type parameters are not context sensitive.
if (node.typeParameters) {
return false;
}
// Functions with any parameters that lack type annotations are context sensitive.
if (forEach(node.parameters, p => !p.type)) {
return true;
}
// For arrow functions we now know we're not context sensitive.
if (node.kind === SyntaxKind.ArrowFunction) {
return false;
}
// If the first parameter is not an explicit 'this' parameter, then the function has
// an implicit 'this' parameter which is subject to contextual typing. Otherwise we
// know that all parameters (including 'this') have type annotations and nothing is
// subject to contextual typing.
const parameter = firstOrUndefined(node.parameters);
return !(parameter && parameter.name.kind === SyntaxKind.Identifier && (<Identifier>parameter.name).text === "this");
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This can be written as !parameterIsThisKeyword(firstOrUndefined(node.parameters))

}

function isContextSensitiveFunctionOrObjectLiteralMethod(func: Node): func is FunctionExpression | ArrowFunction | MethodDeclaration {
Expand Down Expand Up @@ -9629,7 +9640,7 @@ namespace ts {
}
}

const thisType = getThisTypeOfDeclaration(container);
let thisType = getThisTypeOfDeclaration(container) || getContextualThisParameterType(container);
if (thisType) {
return thisType;
}
Expand Down Expand Up @@ -9869,14 +9880,16 @@ namespace ts {
}
}

function getContextualThisParameter(func: FunctionLikeDeclaration): Symbol {
function getContextualThisParameterType(func: FunctionLikeDeclaration): Type {
if (isContextSensitiveFunctionOrObjectLiteralMethod(func) && func.kind !== SyntaxKind.ArrowFunction) {
const contextualSignature = getContextualSignature(func);
if (contextualSignature) {
return contextualSignature.thisParameter;
const thisParameter = contextualSignature.thisParameter;
if (thisParameter) {
return getTypeOfSymbol(thisParameter);
}
}
}

return undefined;
}

Expand Down Expand Up @@ -12840,21 +12853,36 @@ namespace ts {

function assignContextualParameterTypes(signature: Signature, context: Signature, mapper: TypeMapper) {
const len = signature.parameters.length - (signature.hasRestParameter ? 1 : 0);
if (isInferentialContext(mapper)) {
for (let i = 0; i < len; i++) {
const declaration = <ParameterDeclaration>signature.parameters[i].valueDeclaration;
if (declaration.type) {
inferTypes(mapper.context, getTypeFromTypeNode(declaration.type), getTypeAtPosition(context, i));
}
}
}
if (context.thisParameter) {
if (!signature.thisParameter) {
signature.thisParameter = createTransientSymbol(context.thisParameter, undefined);
const parameter = signature.thisParameter;
if (!parameter || parameter.valueDeclaration && !(<ParameterDeclaration>parameter.valueDeclaration).type) {
if (!parameter) {
signature.thisParameter = createTransientSymbol(context.thisParameter, undefined);
}
assignTypeToParameterAndFixTypeParameters(signature.thisParameter, getTypeOfSymbol(context.thisParameter), mapper);
}
assignTypeToParameterAndFixTypeParameters(signature.thisParameter, getTypeOfSymbol(context.thisParameter), mapper);
}
for (let i = 0; i < len; i++) {
const parameter = signature.parameters[i];
const contextualParameterType = getTypeAtPosition(context, i);
assignTypeToParameterAndFixTypeParameters(parameter, contextualParameterType, mapper);
if (!(<ParameterDeclaration>parameter.valueDeclaration).type) {
const contextualParameterType = getTypeAtPosition(context, i);
assignTypeToParameterAndFixTypeParameters(parameter, contextualParameterType, mapper);
}
}
if (signature.hasRestParameter && isRestParameterIndex(context, signature.parameters.length - 1)) {
const parameter = lastOrUndefined(signature.parameters);
const contextualParameterType = getTypeOfSymbol(lastOrUndefined(context.parameters));
assignTypeToParameterAndFixTypeParameters(parameter, contextualParameterType, mapper);
if (!(<ParameterDeclaration>parameter.valueDeclaration).type) {
const contextualParameterType = getTypeOfSymbol(lastOrUndefined(context.parameters));
assignTypeToParameterAndFixTypeParameters(parameter, contextualParameterType, mapper);
}
}
}

Expand Down