typespec1-1  Exercise 3: Four Compiler Errors
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broken.tsp:

  @service(#{ title: "Shelf Service" })
  namespace ShelfService;

  model Shelf {
    id: string;
    capacity: int;
  }

  @route("/shelves")
  interface Shelves {
    @get list(): Shelff[];
  }

PREDICTION (from reading the source)
  line 6   capacity: int         -> int is not a TypeSpec type
  line 9   @route(...)           -> no import of the HTTP library, so @route is unknown
  line 11  Shelff[]              -> a typo for Shelf
  line 11  @get                  -> unknown for the same reason as @route

Output of the compiler, then of the fixed file:

  $ tsp compile broken.tsp
  Diagnostics were reported during compilation:

  ex/broken.tsp:6:13 - error invalid-ref: Unknown identifier int
  ex/broken.tsp:9:2 - error invalid-ref: Unknown decorator @route
  ex/broken.tsp:11:16 - error invalid-ref: Unknown identifier Shelff
  ex/broken.tsp:11:4 - error invalid-ref: Unknown decorator @get

  Found 4 errors.


  $ tsp compile fixed.tsp

  Compilation completed successfully.

fixed.tsp:

  import "@typespec/http";

  using Http;

  @service(#{ title: "Shelf Service" })
  namespace ShelfService;

  model Shelf {
    id: string;
    capacity: int32;
  }

  @route("/shelves")
  interface Shelves {
    @get list(): Shelf[];
  }

THE FIXES
  import "@typespec/http"; and using Http;   (two of the four errors disappear at once)
  int  becomes  int32                        (a sized integer; integer also compiles)
  Shelff  becomes  Shelf

WHY THIS WORKS AS AN ANSWER
---------------------------
The four diagnostics come from three causes, and two of them (@route and @get) share one cause: the HTTP library was never loaded. That is why it pays to fix errors from the top of the file and recompile, because later errors are sometimes consequences. Note that the compiler listed the errors in an order that is not strictly top to bottom (line 6, then 9, then 11 twice, with the column of @get after the typo's): do not rely on the order, read each line number.