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Merge pull request #19912 from Microsoft/fixEmptyArrayInference

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Fix empty array inference
This commit is contained in:
Anders Hejlsberg
2017-11-10 13:48:38 -08:00
committed by GitHub
parent 06dd3f246f c3b650fb38
commit a79610a403
8 changed files with 144 additions and 39 deletions
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17
src/compiler/checker.ts
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@@ -10898,22 +10898,25 @@ namespace ts {
// it as an inference candidate. Hopefully, a better candidate will come along that does
// not contain anyFunctionType when we come back to this argument for its second round
// of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
// when constructing types from type parameters that had no inference candidates) and
// implicitNeverType (which is used as the element type for empty array literals).
if (source.flags & TypeFlags.ContainsAnyFunctionType || source === silentNeverType || source === implicitNeverType) {
// when constructing types from type parameters that had no inference candidates).
if (source.flags & TypeFlags.ContainsAnyFunctionType || source === silentNeverType) {
return;
}
const inference = getInferenceInfoForType(target);
if (inference) {
if (!inference.isFixed) {
if (!inference.candidates || priority < inference.priority) {
// We give lowest priority to inferences of implicitNeverType (which is used as the
// element type for empty array literals). Thus, inferences from empty array literals
// only matter when no other inferences are made.
const p = priority | (source === implicitNeverType ? InferencePriority.NeverType : 0);
if (!inference.candidates || p < inference.priority) {
inference.candidates = [source];
inference.priority = priority;
inference.priority = p;
}
else if (priority === inference.priority) {
else if (p === inference.priority) {
inference.candidates.push(source);
}
if (!(priority & InferencePriority.ReturnType) && target.flags & TypeFlags.TypeParameter && !isTypeParameterAtTopLevel(originalTarget, <TypeParameter>target)) {
if (!(p & InferencePriority.ReturnType) && target.flags & TypeFlags.TypeParameter && !isTypeParameterAtTopLevel(originalTarget, <TypeParameter>target)) {
inference.topLevel = false;
}
}

1
src/compiler/types.ts
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@@ -3613,6 +3613,7 @@ namespace ts {
NakedTypeVariable = 1 << 1, // Naked type variable in union or intersection type
MappedType = 1 << 2, // Reverse inference for mapped type
ReturnType = 1 << 3, // Inference made from return type of generic function
NeverType = 1 << 4, // Inference made from the never type
}
export interface InferenceInfo {