Happy should error out on duplicate productions - Githubissues

haskell / happy

The Happy parser generator for Haskell

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Happy should error out on duplicate productions #158

Open harpocrates opened 4 years ago

harpocrates commented 4 years ago

Consider the following short grammar:
```
foo :: { Int }
  : int             { $1 }

foo :: { Int }
  : int             { $1 + 4 }
```
Happy should not accept this - it should complain that I've defined foo twice. Right now, it just silently picks one of the two.
Consider the following shorter grammar:
```
foo :: { Int }
foob
  : int             { $1 }
```
Happy should not accept this - it should complain that the name foob does not match the expected name foo. Right now, it just uses foo and ignores foob completely.