Add readonly check to property access of index signature#17710
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sandersn merged 3 commits intoAug 16, 2017
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Unfortunately, the checking code isn't reusable in a large chunk, so I copied it from `getPropertyTypeForIndexType`. It still might be better to extract the four lines to report the error into its own function.
weswigham
approved these changes
Aug 9, 2017
rbuckton
suggested changes
Aug 10, 2017
| if (indexInfo && indexInfo.type) { | ||
| if (indexInfo.isReadonly && (isAssignmentTarget(node) || isDeleteTarget(node))) { | ||
| error(node, Diagnostics.Index_signature_in_type_0_only_permits_reading, typeToString(apparentType)); | ||
| return unknownType; |
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Should we return unknownType here? We know the type, even if the access is invalid.
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Agree with Ron. You should fix this in the other place where we perform a read-only check.
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Good catch. Always happy to remove bad code! 💯
ahejlsberg
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Aug 10, 2017
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Approved with the requested changes.
| if (indexInfo && indexInfo.type) { | ||
| if (indexInfo.isReadonly && (isAssignmentTarget(node) || isDeleteTarget(node))) { | ||
| error(node, Diagnostics.Index_signature_in_type_0_only_permits_reading, typeToString(apparentType)); | ||
| return unknownType; |
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Agree with Ron. You should fix this in the other place where we perform a read-only check.
Now, in an assignment to an indexed access of a readonly property, the resulting type is still the property's type. Previously it was unknownType. This improves error reporting slightly by reporting some errors that were previously missed.
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Fixes #14296
Unfortunately, the checking code isn't reusable in a large chunk, so I copied it from
getPropertyTypeForIndexType. It still might be better to extract the four lines to report the error into its own function.