Hadrian failure after worktree update

[Bryan Richter]

Below is an error message I have seen a number of times after
rebasing my git worktree, i.e. this is how to "reproduce":

    git fetch origin
    git rebase origin/master
    git submodule update
    ./hadrian/build.sh

(Obviously some details are elided, and this is not a complete reproduction.)

I don't have many copies of the error, but I do remember seeing the
complaint about "No generator for .../PmOracle.hs" on other occasions.

Any idea what this comes from?

-Bryan

--- 8< ---

Error when running Shake build system:
  at action, called at src/Rules.hs:71:19 in main:Rules
  at need, called at src/Rules.hs:93:5 in main:Rules
* Depends on: _build/stage0/lib/package.conf.d/ghc-8.9.0.20190929.conf
  at need, called at src/Rules/Register.hs:113:5 in main:Rules.Register
* Depends on: _build/stage0/compiler/build/libHSghc-8.9.0.20190929.a
* Depends on: _build/stage0/compiler/build/GHCi.o
* Depends on: _build/stage0/compiler/build/GHCi.o _build/stage0/compiler/build/GHCi.hi
* Depends on: OracleQ (KeyValues ("_build/stage0/compiler/.dependencies","_build/stage0/compiler/build/GHCi.o"))
* Depends on: _build/stage0/compiler/.dependencies
* Depends on: _build/stage0/compiler/.dependencies.mk
  at need, called at src/Rules/Dependencies.hs:26:9 in main:Rules.Dependencies
* Depends on: _build/stage0/compiler/build/PmOracle.hs
  at error, called at src/Rules/Generate.hs:105:34 in main:Rules.Generate
* Raised the exception:
No generator for _build/stage0/compiler/build/PmOracle.hs.