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Simon Jakobi pushed to branch wip/sjakobi/T22637-v2 at Glasgow Haskell Compiler / GHC

Commits:

bcd7d99b

by Simon Jakobi at 2026-04-10T18:53:13+02:00

Show multiple carets for TcRnBindingNameConflict

When a name is bound multiple times (e.g. `f x x = 2`), the error now
shows carets for all binding locations:

    TcRnBindingNameConflict.hs:3:3: error: [GHC-10498]
        • Conflicting definitions for 'x'
          Bound at: TcRnBindingNameConflict.hs:3:3
                    TcRnBindingNameConflict.hs:3:5
        • In an equation for 'f'
      |
    3 | f x x = 2
      |   ^
      |
    3 | f x x = 2
      |     ^

This is achieved by implementing `diagnosticSourceSpans` for
`TcRnBindingNameConflict`, which already carries multiple source
locations as `NonEmpty SrcSpan`.

d318c190

by Simon Jakobi at 2026-04-10T20:19:16+02:00

Update tests for multi-caret TcRnBindingNameConflict diagnostics

Updated tests to use -fdiagnostics-show-caret now that
TcRnBindingNameConflict shows carets for all binding locations:

- rnfail004: Shows carets for 'a' and 'b' conflicts across lines
- tcfail038: Shows carets for '==' and '/=' on different lines
- T14114: Shows carets for both 'a' positions in pattern (a,a)

7 changed files:

compiler/GHC/Tc/Errors/Ppr.hs
testsuite/tests/patsyn/should_fail/T14114.stderr
testsuite/tests/patsyn/should_fail/all.T
testsuite/tests/rename/should_fail/all.T
testsuite/tests/rename/should_fail/rnfail004.stderr
testsuite/tests/typecheck/should_fail/all.T
testsuite/tests/typecheck/should_fail/tcfail038.stderr

Changes:

compiler/GHC/Tc/Errors/Ppr.hs

@@ -3479,6 +3479,11 @@ instance Diagnostic TcRnMessage where
           NE.fromList $
           sortBy leftmost_smallest $
           map (getLocA . fst) (NE.toList pairs)
 +    TcRnBindingNameConflict _ locs
 +      -> Just $
 +         NE.fromList $
 +         sortBy leftmost_smallest $
 +         NE.toList locs
      _ ->
        Nothing

testsuite/tests/patsyn/should_fail/T14114.stderr

  T14114.hs:4:20: error: [GHC-10498]
 -    • Conflicting definitions for ‘a’
 +    • Conflicting definitions for 'a'
        Bound at: T14114.hs:4:20
                  T14114.hs:4:22
      • In a pattern synonym declaration
 +  |
 +4 | pattern Foo1 a <- (a,a)
 +  |                    ^
 +  |
 +4 | pattern Foo1 a <- (a,a)
 +  |                      ^
  T14114.hs:5:20: error: [GHC-10498]
 -    • Conflicting definitions for ‘a’
 +    • Conflicting definitions for 'a'
        Bound at: T14114.hs:5:20
                  T14114.hs:5:22
      • In a pattern synonym declaration
 +  |
 +5 | pattern Foo2 a  = (a,a)
 +  |                    ^
 +  |
 +5 | pattern Foo2 a  = (a,a)
 +  |                      ^
  T14114.hs:6:20: error: [GHC-10498]
 -    • Conflicting definitions for ‘a’
 +    • Conflicting definitions for 'a'
        Bound at: T14114.hs:6:20
                  T14114.hs:6:22
      • In a pattern synonym declaration
 +  |
 +6 | pattern Foo3 a <- (a,a) where
 +  |                    ^
 +  |
 +6 | pattern Foo3 a <- (a,a) where
 +  |                      ^

testsuite/tests/patsyn/should_fail/all.T

@@ -40,7 +40,7 @@ test('T26465', normal, compile_fail, [''])
  test('T13349', normal, compile_fail, [''])
  test('T13470', normal, compile_fail, [''])
  test('T14112', normal, compile_fail, [''])
 -test('T14114', normal, compile_fail, [''])
 +test('T14114', normal, compile_fail, ['-fdiagnostics-show-caret'])
  test('T14507', normal, compile_fail, ['-dsuppress-uniques'])
  test('T15289', normal, compile_fail, [''])
  test('T15685', normal, compile_fail, [''])

testsuite/tests/rename/should_fail/all.T

  test('rnfail001', normal, compile_fail, [''])
  test('rnfail002', normal, compile_fail, [''])
  test('rnfail003', normal, compile_fail, [''])
 -test('rnfail004', normal, compile_fail, [''])
 +test('rnfail004', normal, compile_fail, ['-fdiagnostics-show-caret'])
  test('rnfail007', normal, compile_fail, [''])
  test('rnfail008', normal, compile_fail, [''])
  test('rnfail009', normal, compile_fail, [''])

testsuite/tests/rename/should_fail/rnfail004.stderr

 -rnfail004.hs:6:5: [GHC-10498]
 -    Conflicting definitions for ‘a’
 +rnfail004.hs:6:5: error: [GHC-10498]
 +    Conflicting definitions for 'a'
      Bound at: rnfail004.hs:6:5
                rnfail004.hs:7:10
 +  |
 +6 |     a           = []
 +  |     ^
 +  |
 +7 |     (b,c,a)     = ([],[],d)
 +  |          ^
 -rnfail004.hs:7:6: [GHC-10498]
 -    Conflicting definitions for ‘b’
 +rnfail004.hs:7:6: error: [GHC-10498]
 +    Conflicting definitions for 'b'
      Bound at: rnfail004.hs:7:6
                rnfail004.hs:8:8
 +  |
 +7 |     (b,c,a)     = ([],[],d)
 +  |      ^
 +  |
 +8 |     [d,b,_]     = ([],a,[])
 +  |        ^

testsuite/tests/typecheck/should_fail/all.T

@@ -31,7 +31,7 @@ test('tcfail034', normal, compile_fail, [''])
  test('tcfail035', normal, compile_fail, [''])
  test('tcfail036', normal, compile_fail, [''])
  test('tcfail037', normal, compile_fail, [''])
 -test('tcfail038', normal, compile_fail, [''])
 +test('tcfail038', normal, compile_fail, ['-fdiagnostics-show-caret'])
  test('tcfail040', normal, compile_fail, [''])
  test('tcfail041', normal, compile_fail, [''])
  test('tcfail042', normal, compile_fail, [''])

testsuite/tests/typecheck/should_fail/tcfail038.stderr

 -tcfail038.hs:7:11: [GHC-10498]
 -    Conflicting definitions for ‘==’
 +tcfail038.hs:7:11: error: [GHC-10498]
 +    Conflicting definitions for '=='
      Bound at: tcfail038.hs:7:11-12
                tcfail038.hs:9:11-12
 +  |
 +7 |         a == b = True
 +  |           ^^
 +  |
 +9 |         a == b = False
 +  |           ^^
 -tcfail038.hs:8:11: [GHC-10498]
 -    Conflicting definitions for ‘/=’
 +tcfail038.hs:8:11: error: [GHC-10498]
 +    Conflicting definitions for '/='
      Bound at: tcfail038.hs:8:11-12
                tcfail038.hs:10:11-12
 +   |
 + 8 |         a /= b = False
 +   |           ^^
 +   |
 +10 |         a /= b = True
 +   |           ^^