holeErrors.lean:3:14-3:20: error: don't know how to synthesize implicit argument `α`
  @id ?m
context:
⊢ Sort u
holeErrors.lean:3:4-3:10: error(lean.inferDefTypeFailed): Failed to infer type of definition `f1.{u}`
holeErrors.lean:5:9-5:10: error(lean.inferDefTypeFailed): Failed to infer type of definition `f2`

Note: Because this declaration's type has been explicitly provided, all parameter types and holes (e.g., `_`) in its header are resolved before its body is processed; information from the declaration body cannot be used to infer what these values should be
holeErrors.lean:8:9-8:15: error: don't know how to synthesize implicit argument `α`
  @id ?m
context:
⊢ Sort u
holeErrors.lean:8:4-8:5: error: failed to infer `let` declaration type
holeErrors.lean:7:4-7:10: error(lean.inferDefTypeFailed): Failed to infer type of definition `f3.{u}`
holeErrors.lean:11:4-11:6: error(lean.inferDefTypeFailed): Failed to infer type of definition `f4`
holeErrors.lean:11:8-11:9: error(lean.inferBinderTypeFailed): Failed to infer type of binder `x`
holeErrors.lean:13:4-13:6: error(lean.inferDefTypeFailed): Failed to infer type of definition `f5`
holeErrors.lean:13:8-13:9: error(lean.inferBinderTypeFailed): Failed to infer type of binder `x`
holeErrors.lean:16:4-16:5: error(lean.inferBinderTypeFailed): Failed to infer type of binder `x`
holeErrors.lean:15:4-15:6: error(lean.inferDefTypeFailed): Failed to infer type of definition `f6`
holeErrors.lean:19:13-19:19: error: don't know how to synthesize implicit argument `α`
  @id ?m
context:
⊢ Sort u
holeErrors.lean:19:8-19:9: error: failed to infer 'let rec' declaration type