#10420: "Care with plugin imports" is wrong / orphan RULE visibility -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Description changed by ezyang: Old description:

A module loaded by a plugin poisons the module cache, so we never load an orphan RULE or instance even if we legitimately should do so. The way to test this is a bit convoluted, but it goes something like this:

plugins07.hs {{{ module Main where

import Plugins07a import RuleDefiningPlugin

{-# NOINLINE x #-} x = "foo"

main = putStrLn (show x) }}}

Plugins07a.hs {{{ --{-# OPTIONS_GHC -fplugin RuleDefiningPlugin #-} module Plugins07a where }}}

RuleDefiningPlugin.hs, in ANOTHER PACKAGE (otherwise, EPT rules don't apply) {{{ module RuleDefiningPlugin where

import GhcPlugins

{-# RULES "unsound" forall x. show x = "SHOWED" #-}

plugin :: Plugin plugin = defaultPlugin }}}

I'll commit the full test.

Here's what happens:

* Building `Plugins07a` results in `loadPluginInterface` on `RuleDefiningPlugin`. We load the `ModIface` but only add its types to the environment because of the "Care with plugin imports" special case.

* Building `plugins07.hs` results in a normal source level import for `RuleDefiningPlugin`, but `ModIface` is already in the cache so we don't load anything. RULE is not loaded, disaster!

Admittedly, actually triggering this bug requires a convoluted chain of events. But really this problem arose because the "Care with plugin imports" fix is just completely nonsense. Here's what we should do:

* We should apply the same fix from #2182 on orphan instances to orphan rules too. This way, we can safely load RULEs into the EPS without accidentally bringing them into scope when they shouldn't be.

* Loading an interface should unconditionally suck in the instances and rules.

The result is more correct and simpler, so it seems worth fixing.

New description: A module loaded by a plugin poisons the module cache, so we never load an orphan RULE or instance even if we legitimately should do so. The way to test this is a bit convoluted, but it goes something like this: plugins07.hs {{{ module Main where import Plugins07a import RuleDefiningPlugin {-# NOINLINE x #-} x = "foo" main = putStrLn (show x) }}} Plugins07a.hs {{{ {-# OPTIONS_GHC -fplugin RuleDefiningPlugin #-} module Plugins07a where }}} RuleDefiningPlugin.hs, in ANOTHER PACKAGE (otherwise, EPT rules don't apply) {{{ module RuleDefiningPlugin where import GhcPlugins {-# RULES "unsound" forall x. show x = "SHOWED" #-} plugin :: Plugin plugin = defaultPlugin }}} I'll commit the full test. Here's what happens: * Building `Plugins07a` results in `loadPluginInterface` on `RuleDefiningPlugin`. We load the `ModIface` but only add its types to the environment because of the "Care with plugin imports" special case. * Building `plugins07.hs` results in a normal source level import for `RuleDefiningPlugin`, but `ModIface` is already in the cache so we don't load anything. RULE is not loaded, disaster! Admittedly, actually triggering this bug requires a convoluted chain of events. But really this problem arose because the "Care with plugin imports" fix is just completely nonsense. Here's what we should do: * We should apply the same fix from #2182 on orphan instances to orphan rules too. This way, we can safely load RULEs into the EPS without accidentally bringing them into scope when they shouldn't be. * Loading an interface should unconditionally suck in the instances and rules. The result is more correct and simpler, so it seems worth fixing. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10420#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10420: "Care with plugin imports" is wrong / orphan RULE visibility -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: None/Unknown | Test Case: plugins07 Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by ezyang): * testcase: => plugins07 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10420#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10420: "Care with plugin imports" is wrong / orphan RULE visibility -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: None/Unknown | Test Case: plugins07 Blocked By: | Blocking: 10294 Related Tickets: | Differential Revisions: Phab:D950 -------------------------------------+------------------------------------- Changes (by ezyang): * priority: low => normal Comment: Marking higher since this can affect non-orphan instances too, see #10294 for an example. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10420#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10420: "Care with plugin imports" is wrong / orphan RULE visibility -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Keywords: Resolution: fixed | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: None/Unknown | Test Case: plugins07 Blocked By: | Blocking: 10294 Related Tickets: | Differential Revisions: Phab:D950 -------------------------------------+------------------------------------- Changes (by ezyang): * status: patch => closed * resolution: => fixed -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10420#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler