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Support infix operator rules #1836

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6598e54
Support infix operator rules
msujew Mar 11, 2025
9141ddb
Fix completion test
msujew Mar 11, 2025
ca70591
Fix binary expression parsing
msujew Mar 17, 2025
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14 changes: 2 additions & 12 deletions examples/arithmetics/src/language-server/arithmetics.langium
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Expand Up @@ -20,19 +20,9 @@ Evaluation:
expression=Expression ';';

Expression:
Addition;
BinaryExpression;

Addition infers Expression:
Multiplication ({infer BinaryExpression.left=current} operator=('+' | '-') right=Multiplication)*;

Multiplication infers Expression:
Exponentiation ({infer BinaryExpression.left=current} operator=('*' | '/') right=Exponentiation)*;

Exponentiation infers Expression:
Modulo ({infer BinaryExpression.left=current} operator='^' right=Modulo)*;

Modulo infers Expression:
PrimaryExpression ({infer BinaryExpression.left=current} operator='%' right=PrimaryExpression)*;
infix BinaryExpression on PrimaryExpression: '%' > '^' > '*' | '/' > '+' | '-';
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Normally the precedence of > is greater than the one of |. It reads a bit unnatural.
Adding parentheses could be an option to enumerate all alternatives.
Or maybe a equal sign instead of the |.
WDYT?

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And why not using the comma operator instead of '>' ?

'%' , '^' , '*' | '/' , '+' | '-';

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‚>‘ implies an order between the operators, that makes totally sense to me. Having a comma, you do not know what comes first: low or high precedence. But you can assume some convention, true.

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You can mitigate this by writing each group in its own line:

infix BinaryExpression on PrimaryExpression:
    '%'
    > '^'
    > '*' | '/'
    > '+' | '-';

This is how I'd format such expressions for readability.


PrimaryExpression infers Expression:
'(' Expression ')' |
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285 changes: 40 additions & 245 deletions examples/arithmetics/src/language-server/generated/grammar.ts
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Expand Up @@ -30,7 +30,7 @@ export const ArithmeticsGrammar = (): Grammar => loadedArithmeticsGrammar ?? (lo
"terminal": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@12"
"$ref": "#/rules@9"
},
"arguments": []
}
Expand Down Expand Up @@ -102,7 +102,7 @@ export const ArithmeticsGrammar = (): Grammar => loadedArithmeticsGrammar ?? (lo
"terminal": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@12"
"$ref": "#/rules@9"
},
"arguments": []
}
Expand Down Expand Up @@ -194,7 +194,7 @@ export const ArithmeticsGrammar = (): Grammar => loadedArithmeticsGrammar ?? (lo
"terminal": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@12"
"$ref": "#/rules@9"
},
"arguments": []
}
Expand Down Expand Up @@ -255,270 +255,65 @@ export const ArithmeticsGrammar = (): Grammar => loadedArithmeticsGrammar ?? (lo
"wildcard": false
},
{
"$type": "ParserRule",
"name": "Addition",
"inferredType": {
"$type": "InferredType",
"name": "Expression"
"$type": "InfixRule",
"name": "BinaryExpression",
"call": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@7"
},
"arguments": []
},
"definition": {
"$type": "Group",
"elements": [
{
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@7"
},
"arguments": []
},
"operators": {
"$type": "InfixRuleOperators",
"precedences": [
{
"$type": "Group",
"elements": [
"$type": "InfixRuleOperatorList",
"operators": [
{
"$type": "Action",
"inferredType": {
"$type": "InferredType",
"name": "BinaryExpression"
},
"feature": "left",
"operator": "="
},
{
"$type": "Assignment",
"feature": "operator",
"operator": "=",
"terminal": {
"$type": "Alternatives",
"elements": [
{
"$type": "Keyword",
"value": "+"
},
{
"$type": "Keyword",
"value": "-"
}
]
}
},
{
"$type": "Assignment",
"feature": "right",
"operator": "=",
"terminal": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@7"
},
"arguments": []
}
"$type": "Keyword",
"value": "%"
}
],
"cardinality": "*"
}
]
},
"definesHiddenTokens": false,
"entry": false,
"fragment": false,
"hiddenTokens": [],
"parameters": [],
"wildcard": false
},
{
"$type": "ParserRule",
"name": "Multiplication",
"inferredType": {
"$type": "InferredType",
"name": "Expression"
},
"definition": {
"$type": "Group",
"elements": [
{
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@8"
},
"arguments": []
]
},
{
"$type": "Group",
"elements": [
{
"$type": "Action",
"inferredType": {
"$type": "InferredType",
"name": "BinaryExpression"
},
"feature": "left",
"operator": "="
},
"$type": "InfixRuleOperatorList",
"operators": [
{
"$type": "Assignment",
"feature": "operator",
"operator": "=",
"terminal": {
"$type": "Alternatives",
"elements": [
{
"$type": "Keyword",
"value": "*"
},
{
"$type": "Keyword",
"value": "/"
}
]
}
},
{
"$type": "Assignment",
"feature": "right",
"operator": "=",
"terminal": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@8"
},
"arguments": []
}
"$type": "Keyword",
"value": "^"
}
],
"cardinality": "*"
}
]
},
"definesHiddenTokens": false,
"entry": false,
"fragment": false,
"hiddenTokens": [],
"parameters": [],
"wildcard": false
},
{
"$type": "ParserRule",
"name": "Exponentiation",
"inferredType": {
"$type": "InferredType",
"name": "Expression"
},
"definition": {
"$type": "Group",
"elements": [
{
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@9"
},
"arguments": []
]
},
{
"$type": "Group",
"elements": [
{
"$type": "Action",
"inferredType": {
"$type": "InferredType",
"name": "BinaryExpression"
},
"feature": "left",
"operator": "="
},
"$type": "InfixRuleOperatorList",
"operators": [
{
"$type": "Assignment",
"feature": "operator",
"operator": "=",
"terminal": {
"$type": "Keyword",
"value": "^"
}
"$type": "Keyword",
"value": "*"
},
{
"$type": "Assignment",
"feature": "right",
"operator": "=",
"terminal": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@9"
},
"arguments": []
}
"$type": "Keyword",
"value": "/"
}
],
"cardinality": "*"
}
]
},
"definesHiddenTokens": false,
"entry": false,
"fragment": false,
"hiddenTokens": [],
"parameters": [],
"wildcard": false
},
{
"$type": "ParserRule",
"name": "Modulo",
"inferredType": {
"$type": "InferredType",
"name": "Expression"
},
"definition": {
"$type": "Group",
"elements": [
{
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@10"
},
"arguments": []
]
},
{
"$type": "Group",
"elements": [
{
"$type": "Action",
"inferredType": {
"$type": "InferredType",
"name": "BinaryExpression"
},
"feature": "left",
"operator": "="
},
"$type": "InfixRuleOperatorList",
"operators": [
{
"$type": "Assignment",
"feature": "operator",
"operator": "=",
"terminal": {
"$type": "Keyword",
"value": "%"
}
"$type": "Keyword",
"value": "+"
},
{
"$type": "Assignment",
"feature": "right",
"operator": "=",
"terminal": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@10"
},
"arguments": []
}
"$type": "Keyword",
"value": "-"
}
],
"cardinality": "*"
]
}
]
},
"definesHiddenTokens": false,
"entry": false,
"fragment": false,
"hiddenTokens": [],
"parameters": [],
"wildcard": false
"parameters": []
},
{
"$type": "ParserRule",
Expand Down Expand Up @@ -567,7 +362,7 @@ export const ArithmeticsGrammar = (): Grammar => loadedArithmeticsGrammar ?? (lo
"terminal": {
"$type": "RuleCall",
"rule": {
"$ref": "#/rules@13"
"$ref": "#/rules@10"
},
"arguments": []
}
Expand Down
2 changes: 1 addition & 1 deletion packages/langium-cli/src/generator/langium-util.ts
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Expand Up @@ -29,7 +29,7 @@ export function collectKeywords(grammar: Grammar): string[] {
const reachableRules = GrammarUtils.getAllReachableRules(grammar, false);

for (const keyword of stream(reachableRules)
.filter(GrammarAST.isParserRule)
.filter(rule => GrammarAST.isParserRule(rule) || GrammarAST.isInfixRule(rule))
.flatMap(rule => AstUtils.streamAllContents(rule).filter(GrammarAST.isKeyword))) {
keywords.add(keyword.value);
}
Expand Down
2 changes: 1 addition & 1 deletion packages/langium-vscode/data/langium.tmLanguage.json
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Expand Up @@ -13,7 +13,7 @@
},
{
"name": "keyword.control.langium",
"match": "\\b(current|entry|extends|fragment|grammar|hidden|import|infer|infers|interface|returns|terminal|type|with)\\b"
"match": "\\b(current|entry|extends|fragment|grammar|hidden|import|infer|infers|infix|interface|returns|terminal|type|with|on)\\b"
},
{
"name": "constant.language.langium",
Expand Down
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