[GHC] #10684: Error cascade when unrelated class derivation fails
#10684: Error cascade when unrelated class derivation fails -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.11 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Pretty minor bug, but I thought I'd point it out: {{{ module A where import Data.Typeable data A = A deriving (Show, Typeable) data B = B A deriving (Show) }}} I get two errors when I expect one: {{{ A.hs:3:28: Can't make a derived instance of `Typeable A': You need -XDeriveDataTypeable to derive an instance for this class In the data declaration for `A' A.hs:4:24: No instance for (Show A) arising from the 'deriving' clause of a data type declaration Possible fix: add an instance declaration for (Show A) or use a standalone 'deriving instance' declaration, so you can specify the instance context yourself When deriving the instance for (Show B) }}} The failed Typeable derivation also causes the Show derivation to fail, which causes an error later in the file. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10684 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10684: Error cascade when unrelated class derivation fails -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * cc: RyanGlScott (added) Comment: Since all datatypes now have `Typeable` derived implicitly, here's a modern version of this bug: {{{#!hs module A where import GHC.Generics data A = A deriving (Show, Generic) data B = B A deriving (Show) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10684#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10684: Error cascade when unrelated class derivation fails -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): See #12801 for another example -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10684#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10684: Error cascade when unrelated class derivation fails -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: patch Priority: low | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3771 Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: new => patch * differential: => Phab:D3771 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10684#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10684: Error cascade when unrelated class derivation fails
-------------------------------------+-------------------------------------
Reporter: ezyang | Owner: (none)
Type: bug | Status: patch
Priority: low | Milestone:
Component: Compiler (Type | Version: 7.11
checker) |
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s): Phab:D3771
Wiki Page: |
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Comment (by Ryan Scott
#10684: Error cascade when unrelated class derivation fails -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: closed Priority: low | Milestone: 8.4.1 Component: Compiler (Type | Version: 7.11 checker) | Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | deriving/should_fail/T10684 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3771 Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: patch => closed * testcase: => deriving/should_fail/T10684 * resolution: => fixed * milestone: => 8.4.1 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10684#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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