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Look-ahead for arrow function expressions too permissive when encountering "()" #34

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DanielRosenwasser opened this issue Jul 16, 2014 · 2 comments
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Look-ahead for arrow function expressions too permissive when encountering "()" #34

DanielRosenwasser opened this issue Jul 16, 2014 · 2 comments
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@DanielRosenwasser
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Bug A bug in TypeScript Fixed A PR has been merged for this issue
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TypeScript 1.5

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@DanielRosenwasser
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When encountering code like

().toString();

We make a strange assumption, which is that the () belongs to an arrow function like the following:

() => x

This is weird because it bubbles up to nothing better than the error

Cannot find name 'toString'.

In this case, we should check to see if the next token is an arrow (=>).
@DanielRosenwasser DanielRosenwasser mentioned this issue Jul 16, 2014
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@DanielRosenwasser DanielRosenwasser self-assigned this Jul 16, 2014
@JsonFreeman
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Make sure to check if the next token is either an arrow or open brace. The open brace corresponds to a function expression where the user forgot the arrow.

@sophiajt sophiajt added the Bug label Jul 16, 2014
@sophiajt sophiajt added this to the TypeScript 2.0 milestone Jul 16, 2014
DanielRosenwasser added a commit that referenced this issue Jul 22, 2014
@DanielRosenwasser
Improved lookahead for arrow functions.
426e8e5 
Fixes issue #34.

Specifically:
    * We no longer automatically assume "()" is a function expression. It must be followed by an arrow, colon, or curly brace.
    * If an arrow is missing following a signature, but a curly brace is present, we assume the user forgot the arrow and try to parse the body anyway.
DanielRosenwasser added a commit that referenced this issue Jul 23, 2014
@DanielRosenwasser
Improved lookahead for arrow functions.
5b6bb5b 
Fixes issue #34.

Specifically:
    * We no longer automatically assume "()" is a function expression. It must be followed by an arrow, colon, or curly brace.
    * If an arrow is missing following a signature, but a curly brace is present, we assume the user forgot the arrow and try to parse the body anyway.
@DanielRosenwasser DanielRosenwasser mentioned this issue Jul 23, 2014
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@DanielRosenwasser
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Addressed in #203, with the potential "issue" that

a ? () : c

parses as a lambda as well.

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@sophiajt @DanielRosenwasser @mhegazy @JsonFreeman