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Fix 'oneof' in syntax-directed operations #637

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merged 5 commits into from
Mar 26, 2025
Merged

Fix 'oneof' in syntax-directed operations #637

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311e348
Fix 'oneof' in syntax-directed operations
szuend Mar 10, 2025
e006077
Use subset instead of equality when matching one-of lists for SDOs
szuend Mar 11, 2025
286f296
Change tests so usage of 'one of' makes sense
szuend Mar 12, 2025
50b85b7
Add 'default' branch back in
szuend Mar 13, 2025
e487350
Merge branch 'main' into fix-one-of-sdo
bakkot Mar 26, 2025
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12 changes: 10 additions & 2 deletions src/lint/utils.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -73,8 +73,8 @@ export function rhsMatches(a: RightHandSide | OneOfList, b: RightHandSide | OneO
}
return symbolSpanMatches(aHead, bHead);
}
default:
throw new Error('unknown rhs type ' + a.constructor.name);
case SyntaxKind.OneOfList:
return oneOfListMatches(a, b as OneOfList);
}
}

Expand Down Expand Up @@ -171,6 +171,14 @@ function argumentListMatches(a: ArgumentList, b: ArgumentList) {
);
}

function oneOfListMatches(a: OneOfList, b: OneOfList) {
if (a.terminals === undefined || b.terminals === undefined) {
throw new Error('OneOfList must have terminals');
}
// The terminals in a must be a subset of the terminals in b.
return a.terminals.every(ae => b.terminals!.find(be => ae.text === be.text));
}

// this is only for use with single-file grammars
export function getLocationInGrammarFile(file: SourceFile, pos: number) {
const posWithoutWhitespace = skipTrivia(file.text, pos, file.text.length);
Expand Down
69 changes: 69 additions & 0 deletions test/errors.js
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Expand Up @@ -1106,6 +1106,31 @@ ${M} </pre>
);
});

it('unknown oneof', async () => {
await assertError(
positioned`
<emu-grammar type="definition">
Foo :: one of \`a\` \`b\` \`c\`
</emu-grammar>

<emu-clause id="sec-example" type="sdo">
<h1>Static Semantics: Example</h1>
<dl class='header'></dl>
<emu-grammar>
Foo :: ${M}one of \`d\`
</emu-grammar>
<emu-alg>
1. Return *true*.
</emu-alg>
</emu-clause>`,
{
ruleId: 'grammar-shape',
nodeType: 'emu-grammar',
message: 'could not find definition for rhs "d"',
},
);
});

it('negative', async () => {
await assertErrorFree(`
<emu-grammar type="definition">
Expand Down Expand Up @@ -1167,5 +1192,49 @@ ${M} </pre>
},
);
});

it('negative: oneof', async () => {
await assertErrorFree(`
<emu-grammar type="definition">
Foo :: one of \`a\` \`b\` \`c\`
</emu-grammar>

<emu-clause id="sec-example" type="sdo">
<h1>Static Semantics: Example</h1>
<dl class='header'></dl>
<emu-grammar>
Foo :: one of \`a\` \`b\` \`c\`
</emu-grammar>
<emu-alg>
1. Return *true*.
</emu-alg>
</emu-clause>
`);
});

it('negative: oneof (subset)', async () => {
await assertErrorFree(`
<emu-grammar type="definition">
Foo :: one of \`a\` \`b\` \`c\`
</emu-grammar>

<emu-clause id="sec-example" type="sdo">
<h1>Static Semantics: Example</h1>
<dl class='header'></dl>
<emu-grammar>
Foo :: one of \`a\`
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This should read

Suggested change
Foo :: one of \`a\`
Foo :: \`a\`

We should prohibit "one of" with only one alternative.

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I changed the test to Foo :: one of `a` `b` instead. Allowing Foo :: `a` should probably be done in a separate PR since it requires changing rhsMatches to compare different kinds of productions. Also disallowing Foo :: one of `a` should probably be done in the linter in a separate PR.

</emu-grammar>
<emu-alg>
1. Return *true*.
</emu-alg>
<emu-grammar>
Foo :: one of \`b\`
</emu-grammar>
<emu-alg>
1. Return *false*.
</emu-alg>
</emu-clause>
`);
});
});
});