Fix return value and error reporting for getIterationTypesOfMethod

[rbuckton]

This fixes getIterationTypesOfMethod to correctly return undefined when the iterator type does not have a valid next method. This also ensures related errors are still reported when we've already cached a noIterationTypes result.

Related #49736

[gabritto]

Thanks for fixing this, I think now the iterator/iterable functions will make more sense.

[rbuckton]

@typescript-bot test this
@typescript-bot user test this

[typescript-bot]

Heya @rbuckton, I've started to run the extended test suite on this PR at 51be560. You can monitor the build here.

[typescript-bot]

Heya @rbuckton, I've started to run the diff-based user code test suite on this PR at 51be560. You can monitor the build here.

Update: The results are in!

[typescript-bot]

Heya @rbuckton, I've run the RWC suite on this PR - assuming you're on the TS core team, you can view the resulting diff here.

[typescript-bot]

@rbuckton
The results of the user tests run you requested are in!

Here they are:

Comparison Report - main..refs/pull/50146/merge

[adonis-framework]

1 of 1 projects failed to build with the old tsc

/mnt/ts_downloads/adonis-framework/tsconfig.json

• error TS2322: Type 'Generator<any, any, unknown>' is not assignable to type 'boolean'.
  • /mnt/ts_downloads/adonis-framework/node_modules/adonis-framework/src/Session/Drivers/Cookie/index.js(77,15)
  • /mnt/ts_downloads/adonis-framework/node_modules/adonis-framework/src/Session/Drivers/Cookie/index.js(88,15)
  • /mnt/ts_downloads/adonis-framework/node_modules/adonis-framework/src/Session/Drivers/Redis/index.js(59,15)
  • /mnt/ts_downloads/adonis-framework/node_modules/adonis-framework/src/Session/Drivers/Redis/index.js(72,15)
  • /mnt/ts_downloads/adonis-framework/node_modules/adonis-framework/src/Session/index.js(168,15)
  • /mnt/ts_downloads/adonis-framework/node_modules/adonis-framework/src/Session/index.js(204,15)
  • /mnt/ts_downloads/adonis-framework/node_modules/adonis-framework/src/Session/index.js(234,15)
  • /mnt/ts_downloads/adonis-framework/node_modules/adonis-framework/src/Session/index.js(287,15)

[rbuckton]

/mnt/ts_downloads/adonis-framework/tsconfig.json

• error TS2322: Type 'Generator<any, any, unknown>' is not assignable to type 'boolean'.

Not actually a new error, this previously said error TS2322: Type 'Generator<any, any, any>' is not assignable to type 'boolean'., so the only difference is the type we show for the error message when checking if a return type is valid for a generator.