Bound methods with non-identifier names cause a crash #858

alangpierce · 2017-02-20T04:49:08Z

decaffeinate is crashing on my CoffeeScript input:

class A
  "#{b}": => c

(repl)

I get this error:

AddVariableDeclarationsStage failed to parse: Unexpected token (3:9)
  1 | class A {
  2 |   constructor() {
> 3 |     this."#{b}" = this."#{b}".bind(this);
    |          ^
  4 |   }
  5 |

Progress toward decaffeinate/decaffeinate#858 The babylon AST has ObjectMethod and ClassMethod keys that are within the method node, which means that we were viewing any assignment within that key as being in the method block, so the variable would get declared in the wrong place. To work around this, we can temporarily set the scope as one higher while we traverse the key part of the method.

Fixes decaffeinate#858 The basic idea is that we make sure all bound method keys are repeatable and that method bindings are patched after the bound method keys are, then use that information if necessary to generate a method binding line using square bracket notation. There were some nuances here: * We now need to change the patching order so constructors are patched last, so that we have the patched values for method names to bind. This means that we need to explicitly do so in BlockPatcher, and in the case where we introduce the constructor, we want to introduce it at the top of the class but after the class contents are patched. Since normally patching needs to be done in order, I added a way to use the `prependLeft` method from magic-string for special cases where we know that patching needs to be done out of order. * Since there's a special case that a `"#{a}"` key turns into `[a]`, we need to properly handle the case where the string expression is repeatable. This requires extending the repeatable protocol a little.

Fixes #858 The basic idea is that we make sure all bound method keys are repeatable and that method bindings are patched after the bound method keys are, then use that information if necessary to generate a method binding line using square bracket notation. There were some nuances here: * We now need to change the patching order so constructors are patched last, so that we have the patched values for method names to bind. This means that we need to explicitly do so in BlockPatcher, and in the case where we introduce the constructor, we want to introduce it at the top of the class but after the class contents are patched. Since normally patching needs to be done in order, I added a way to use the `prependLeft` method from magic-string for special cases where we know that patching needs to be done out of order. * Since there's a special case that a `"#{a}"` key turns into `[a]`, we need to properly handle the case where the string expression is repeatable. This requires extending the repeatable protocol a little.

alangpierce added the crash label Feb 20, 2017

alangpierce self-assigned this Feb 20, 2017

alangpierce mentioned this issue Feb 21, 2017

fix: use the proper scope for assignments within method keys eventualbuddha/add-variable-declarations#52

Merged

alangpierce mentioned this issue Feb 25, 2017

fix: allow computed keys for the names of bound methods #866

Merged

alangpierce closed this in #866 Feb 26, 2017

decaffeinate / decaffeinate

Bound methods with non-identifier names cause a crash #858

Bound methods with non-identifier names cause a crash #858

alangpierce commented Feb 20, 2017

decaffeinate / decaffeinate

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Bound methods with non-identifier names cause a crash #858

Bound methods with non-identifier names cause a crash #858

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alangpierce commented Feb 20, 2017

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