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thorn0 opened this issue Oct 25, 2019 · 4 comments · Fixed by #1141
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Optional chaining: (a?.b).c is parsed as a?.b.c #1139

thorn0 opened this issue Oct 25, 2019 · 4 comments · Fixed by #1141
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bug Something isn't working has pr there is a PR raised to close this package: typescript-estree Issues related to @typescript-eslint/typescript-estree

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@thorn0
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thorn0 commented Oct 25, 2019 •
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prettier/prettier#6657 is blocked by this issue.

What code were you trying to parse?

(a?.b).c

What did you expect to happen?

The outer node should be of type MemberExpresion, not OptionalMemberExpression.

What actually happened?

Both member expressions are OptionalMemberExpression as if the parens weren't there (a?.b.c).

Versions

package version
@typescript-eslint/typescript-estree 2.5.1-alpha.3
TypeScript 3.7.0-rc
node 10.15.0
npm 6.11.3
@thorn0 thorn0 added package: typescript-estree Issues related to @typescript-eslint/typescript-estree triage Waiting for team members to take a look labels Oct 25, 2019
@thorn0 thorn0 mentioned this issue Oct 25, 2019
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@bradzacher
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bradzacher commented Oct 25, 2019 •
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I don't understand why babel handles this case differently.

It seems to me like this is semantically no different.
Unless I'm mistaken, the parenthesis don't actually change the output or order of execution?

@bradzacher bradzacher added bug Something isn't working and removed triage Waiting for team members to take a look labels Oct 25, 2019
@thorn0
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thorn0 commented Oct 25, 2019 •
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TS compiles

  • a?.b.c to: (_a = a) === null || _a === void 0 ? void 0 : _a.b.c
  • (a?.b).c to: ((_a = a) === null || _a === void 0 ? void 0 : _a.b).c

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@bradzacher
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bradzacher commented Oct 25, 2019 •
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Hmmm yes, I am mistaken - it does change the order of execution and thus the return values and types.

type T = Record<string, Record<string, string>>;
declare const x: T | undefined;

const v1 = x?.a.b;
const v2 = (x?.a).b;
//         ^^^^^^ Object is possibly 'undefined'.
const v3 = (x?.a)?.b;

@thorn0
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thorn0 commented Oct 25, 2019 •
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Yep, it's tricky.

@bradzacher bradzacher added the has pr there is a PR raised to close this label Oct 25, 2019
@bradzacher bradzacher mentioned this issue Oct 25, 2019
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bug Something isn't working has pr there is a PR raised to close this package: typescript-estree Issues related to @typescript-eslint/typescript-estree
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fix(typescript-estree): correct parenthesized optional chain AST typescript-eslint/typescript-eslint
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