Continuing on from the release of TypeScript 3.0, we're committed to improving the user experience all around, and following up on both #25310 and #25257.

Error improvements

• Better errors on object properties in function/constructor calls (Errors not reported on properties inside function calls #25695)
• Better hints for uncalled types ("Did you forget to call 'X'?" for assignability errors #25308)
• Better errors between callable types and unions (Better errors relating callable/constructable types in unions #26449)
• Better errors for accidentally called type assertions (Better errors when accidentally calling type-assertion expressions #26991)
• Better hints for 'cannot find name' errors (Better hints for 'cannot find name' errors #25309)
• Better error spans with nested arrays and arrow functions (Show exact error position in arrays & arrow functions #27030)
• Better errors for accidentally called type assertion (Better errors when accidentally calling type-assertion expressions #26991)

(:running_man: implies we have an existing PR)

Related error spans

• Errors on base members with derived classes (Related error spans for derived members in interfaces/classes #25033)
• Too few arguments (Related error spans for too few arguments #25255)
• Mismatched getters/setters (Add related error spans for getter/setters with different types #25002 🏃)
• Errors on multiple default exports (Related error spans for multiple default exports #25032 🏃)

(:running_man: implies we have an existing PR)

Psst, even though the issues are assigned, we'd welcome any help on them!

The following didn't make the cut, or are in 3.2:

• Seek most-overlapping types in unions (Seek most-overlapping types when relating object types in unions #26450)
• Better errors on weak type intersections like IntrinsicAttributes (Simplify error messages against intersections of weak types #24146 🏃‍♂️)
• Better errors when matching implementation signatures (If call doesn’t resolve to an overload signature, issue a better error when the implementation would work #25488)