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cex: always show ε/%empty in counterexamples

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On a case such as
    %%
    exp
    : empty "a"
    | "a" empty

    empty
    : %empty

we used to display

    warning: shift/reduce conflict on token "a" [-Wcounterexamples]
    Example: • "a"
    Shift derivation
      exp
      ↳ 2: • "a" empty
                 ↳ 2: ε
    Example: • "a"
    Reduce derivation
      exp
      ↳ 1: empty  "a"
           ↳ 3: •

where the shift derivation shows an item "2: empty → ε", with an
explicit "ε", but the reduce derivation shows "3: empty → •", without
"ε".

For consistency, let's always show ε/%empty in rules with an empty
rhs:

    Reduce derivation
      exp
      ↳ 1: empty    "a"
           ↳ 3: ε •

* src/derivation.c (derivation_width, derivation_print_tree_impl):
Always show ε/%empty in counterexamples.
* tests/diagnostics.at: Check that case.
* tests/conflicts.at, tests/counterexample.at: Adjust.
This commit is contained in:
Akim Demaille
2020-08-31 07:22:17 +02:00
parent 82d913741b
commit 325ec7d324
6 changed files with 141 additions and 66 deletions
Download Patch File Download Diff File Expand all files Collapse all files

62
tests/diagnostics.at
View File

@@ -532,9 +532,58 @@ exp
exp
: "if" exp "then" exp
| "if" exp "then" exp "else" exp
| exp "+" exp
| "num"
| empty "a"
| "a" empty
empty
: %empty
]],
]],
[1],
[[input.y: <error>error:</error> shift/reduce conflicts: 9 found, 0 expected
input.y: <warning>warning:</warning> shift/reduce conflict on token "a" [<warning>-Wcounterexamples</warning>]
Example: <cex-0><cex-dot>•</cex-dot> <cex-leaf>"a"</cex-leaf><cex-1></cex-1></cex-0>
Shift derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 6: <cex-dot>•</cex-dot><cex-leaf> "a"</cex-leaf><cex-1><cex-step> empty</cex-step></cex-1></cex-step></cex-0>
<cex-1><cex-step> ↳ 6: ε</cex-step></cex-1>
Example: <cex-0><cex-1><cex-dot>•</cex-dot></cex-1> <cex-leaf>"a"</cex-leaf></cex-0>
Reduce derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 5: <cex-1><cex-step>empty</cex-step></cex-1><cex-leaf> "a"</cex-leaf></cex-step></cex-0>
<cex-1><cex-step> ↳ 7: ε<cex-dot> •</cex-dot></cex-step></cex-1>
input.y: <warning>warning:</warning> shift/reduce conflict on token "a" [<warning>-Wcounterexamples</warning>]
Example: <cex-0><cex-dot>•</cex-dot> <cex-leaf>"a"</cex-leaf><cex-1></cex-1></cex-0>
Shift derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 6: <cex-dot>•</cex-dot><cex-leaf> "a"</cex-leaf><cex-1><cex-step> empty</cex-step></cex-1></cex-step></cex-0>
<cex-1><cex-step> ↳ 6: ε</cex-step></cex-1>
Example: <cex-0><cex-1><cex-dot>•</cex-dot></cex-1> <cex-leaf>"a"</cex-leaf></cex-0>
Reduce derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 5: <cex-1><cex-step>empty</cex-step></cex-1><cex-leaf> "a"</cex-leaf></cex-step></cex-0>
<cex-1><cex-step> ↳ 7: ε<cex-dot> •</cex-dot></cex-step></cex-1>
input.y: <warning>warning:</warning> shift/reduce conflict on token "a" [<warning>-Wcounterexamples</warning>]
Example: <cex-0><cex-dot>•</cex-dot> <cex-leaf>"a"</cex-leaf><cex-1></cex-1></cex-0>
Shift derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 6: <cex-dot>•</cex-dot><cex-leaf> "a"</cex-leaf><cex-1><cex-step> empty</cex-step></cex-1></cex-step></cex-0>
<cex-1><cex-step> ↳ 6: ε</cex-step></cex-1>
Example: <cex-0><cex-1><cex-dot>•</cex-dot></cex-1> <cex-leaf>"a"</cex-leaf></cex-0>
Reduce derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 5: <cex-1><cex-step>empty</cex-step></cex-1><cex-leaf> "a"</cex-leaf></cex-step></cex-0>
<cex-1><cex-step> ↳ 7: ε<cex-dot> •</cex-dot></cex-step></cex-1>
input.y: <warning>warning:</warning> shift/reduce conflict on token "a" [<warning>-Wcounterexamples</warning>]
Example: <cex-0><cex-dot>•</cex-dot> <cex-leaf>"a"</cex-leaf><cex-1></cex-1></cex-0>
Shift derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 6: <cex-dot>•</cex-dot><cex-leaf> "a"</cex-leaf><cex-1><cex-step> empty</cex-step></cex-1></cex-step></cex-0>
<cex-1><cex-step> ↳ 6: ε</cex-step></cex-1>
Example: <cex-0><cex-1><cex-dot>•</cex-dot></cex-1> <cex-leaf>"a"</cex-leaf></cex-0>
Reduce derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 5: <cex-1><cex-step>empty</cex-step></cex-1><cex-leaf> "a"</cex-leaf></cex-step></cex-0>
<cex-1><cex-step> ↳ 7: ε<cex-dot> •</cex-dot></cex-step></cex-1>
input.y: <warning>warning:</warning> shift/reduce conflict on token "+" [<warning>-Wcounterexamples</warning>]
@@ -568,6 +617,17 @@ input.y: <warning>warning:</warning> shift/reduce conflict on token "+" [<warnin
Example: <cex-0><cex-1><cex-leaf>"if"</cex-leaf> <cex-leaf>exp</cex-leaf> <cex-leaf>"then"</cex-leaf> <cex-leaf>exp</cex-leaf> <cex-dot>•</cex-dot></cex-1> <cex-leaf>"+"</cex-leaf> <cex-leaf>exp</cex-leaf></cex-0>
Reduce derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 3: <cex-1><cex-step>exp</cex-step></cex-1><cex-leaf> "+"</cex-leaf><cex-leaf> exp</cex-leaf></cex-step></cex-0>
<cex-1><cex-step> ↳ 1: <cex-leaf>"if"</cex-leaf><cex-leaf> exp</cex-leaf><cex-leaf> "then"</cex-leaf><cex-leaf> exp</cex-leaf><cex-dot> •</cex-dot></cex-step></cex-1>
input.y: <warning>warning:</warning> shift/reduce conflict on token "a" [<warning>-Wcounterexamples</warning>]
Example: <cex-0><cex-dot>•</cex-dot> <cex-leaf>"a"</cex-leaf><cex-1></cex-1></cex-0>
Shift derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 6: <cex-dot>•</cex-dot><cex-leaf> "a"</cex-leaf><cex-1><cex-step> empty</cex-step></cex-1></cex-step></cex-0>
<cex-1><cex-step> ↳ 6: ε</cex-step></cex-1>
Example: <cex-0><cex-1><cex-dot>•</cex-dot></cex-1> <cex-leaf>"a"</cex-leaf></cex-0>
Reduce derivation
<cex-0><cex-step>exp</cex-step></cex-0>
<cex-0><cex-step>↳ 5: <cex-1><cex-step>empty</cex-step></cex-1><cex-leaf> "a"</cex-leaf></cex-step></cex-0>
<cex-1><cex-step> ↳ 7: ε<cex-dot> •</cex-dot></cex-step></cex-1>
input.y: <warning>warning:</warning> shift/reduce conflict on token "+" [<warning>-Wcounterexamples</warning>]