Error elaborations should not be de-duped

TypeScript Version: 3.5.1

Search Terms:

• Error message different

Code

interface ExprData {
  mapper : () => unknown,
  blah : string,
}
interface Expr<DataT extends ExprData> {
  mapper : DataT["mapper"],
  blah : DataT["blah"],

  extra : number,
}

declare function where (
  callback : () => Expr<{
    mapper : () => boolean,
    blah : string,
  }>
) : void;

declare function getInvalidWhere () : Expr<{
  mapper : () => (boolean|null),
  blah : string,
}>;

/*
Type 'Expr<{ mapper: () => boolean | null; blah: string; }>' is not assignable to type 'Expr<{ mapper: () => boolean; blah: string; }>'.
  Type '{ mapper: () => boolean | null; blah: string; }' is not assignable to type '{ mapper: () => boolean; blah: string; }'.
    Types of property 'mapper' are incompatible.
      Type '() => boolean | null' is not assignable to type '() => boolean'.
        Type 'boolean | null' is not assignable to type 'boolean'.
          Type 'null' is not assignable to type 'boolean'.
*/
where(() => getInvalidWhere())
/*
  Expected: Same error as above,
  Actual:
    Type 'Expr<{ mapper: () => boolean | null; blah: string; }>' is not assignable to type
    'Expr<{ mapper: () => boolean; blah: string; }>'.
*/
where(() => getInvalidWhere())

Expected behavior:

• Both errors should have the same error message, if they're in the same file.
• Both errors should have the same error message, if they're in different files.

Actual behavior:

• Both errors have different error messages in the same file.
• Both errors have different error messages in different files.

Playground Link:

Playground

Related Issues:

No source file or test is named. Start by reproducing the two calls in the provided TypeScript example and compare diagnostics from the Playground or a local compiler, then trace the compiler's error elaboration and de-duplication path. Done means repeated elaborations retain the same full message in both the same-file and different-file cases.