Design Meeting Notes, 5/8/2020 #38598

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on May 15, 2020

PR Consistent narrowing by discriminant #38311 More-consistent narrowing
- Fixes long-standing issue
- Design limitation was due to some caching issues
- Singleton types still won't narrow to never, which is generally the desired behvioar
Named tuples
- Switching to parameter-style syntax based on poll feedback
- All names must be present or not present
- Names are preserved through most transforms
- Good to go for 4.0
static index signatures on classes
- ASI issues in parsing
- Final approval 👍
Exponential increase in compile time and memory usage #38339 performance issues
- Caused by massive unions (JSX.IntrisicElements[keyof JSX.IntrinsicElements]) going through subtype reduction
- Keep investigating

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