Remove undefined from the type of default initialised parameters when narrowing #14498
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When narrowing, remove optionality from the initial type of parameters with initialisers. Note that the type of the initialiser is not used; its presence just means that the initial type of the parameter can't contain undefined. It could contain any other member of a declared union type.
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@ahejlsberg can you take a look? |
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That is, it's treated as a narrowing instead of removing |
ahejlsberg
requested changes
Mar 7, 2017
src/compiler/checker.ts
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| declaration.initializer && | ||
| getFalsyFlags(declaredType) & TypeFlags.Undefined && | ||
| !(getFalsyFlags(checkExpression(declaration.initializer)) & TypeFlags.Undefined); | ||
| return annotationIncludesUndefined ? getNonNullableType(declaredType) : declaredType; |
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This line is the source if the issue with null I mentioned. It removes both undefined and null. You need to use getTypeWithFacts(declaredType, TypeFacts.NEUndefined) instead.
src/compiler/checker.ts
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| const initialType = assumeInitialized ? (isParameter ? removeOptionalityFromDeclaredType(type, getRootDeclaration(declaration) as VariableLikeDeclaration) : type) : | ||
| type === autoType || type === autoArrayType ? undefinedType : | ||
| includeFalsyTypes(type, TypeFlags.Undefined); | ||
| const flowType = isFlowNarrowable(node, type, !assumeInitialized) ? getFlowTypeOfReference(node, type, initialType, flowContainer) : type; |
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I would keep the isFlowNarrowable logic inside getFlowTypeOfReference, even if it means adding another parameter. Otherwise, you have to always write this combined pattern which is even more complicated.
ahejlsberg
reviewed
Mar 7, 2017
src/compiler/checker.ts
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| let key: string; | ||
| if (!reference.flowNode || assumeInitialized && !(declaredType.flags & TypeFlags.Narrowable)) { | ||
| if (!isFlowNarrowable(reference, declaredType, couldBeUninitialized)) { |
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Just inline the function here. It's not called anywhere else best I can tell.
ahejlsberg
approved these changes
Mar 7, 2017
Merged
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When narrowing, remove optionality from the initial type of parameters with initialisers. Note that the type of the initialiser is not used; its presence just means that the initial type of the parameter
can't contain undefined. It could contain any other member of a declared union type.
This fix builds on the previous fix #12033, but is slightly more complex in that it changes the initial type before control flow analysis rather than just throwing undefined away from the declared type.
The code refactors most of the complexity into
checkIdentifier, out ofgetFlowTypeOfReference, since it's only needed there. Suggestions on simplifying the mess of conditionals are welcome!Fixes #14487
Fixes #14425
Fixes #14236