Second Version

[macabeus]

After nice discussions, the second version of this proposals comes with the following changes:

• add parameter on handle block, to avoid shadowing problem and give more symmetry with catch block (Add "effect" as a parameter in handle block #16)
• doesn't allow to use resume outside of handle block AND must be in handle block directly (What should happen if we perform an effect and there is no handle to catch it? #8) (Statement "resume" really should be restrict to "effect" block? #9)
• throw error if there is an unhandled effect (What should happen if we perform an effect and there is no handle to catch it? #8 (comment))
• perform always should return a value, even if no resume is called (What should happen if we perform an effect and there is no handle to catch it? #8 (comment))

(each commit is one of the changes above)

TODOs

We still need to discuss more about:

• Should we implicitly inject the effects? No @@?
• How will the effect interact with the ecosystem of TypeScript?
• Alternative Syntax to avoid new keywords
• When we could use perform expression?