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feat: add checked as-cast expression 🎯 #215

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Merged
timfennis merged 8 commits into from
Sep 2, 2026
Merged

feat: add checked as-cast expression 🎯 #215

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d9173c6
test(analyser): pin the type rules for dispatch and augmented assignm…
timfennis Sep 2, 2026
0daca8d
feat: add checked as-cast expression 🎯
timfennis Sep 2, 2026
33251e5
feat(tree-sitter): support `as` in the grammar and editor queries 🌳
timfennis Sep 2, 2026
7505cc8
feat(analyser): suggest a cast when only the argument type is too wide 💡
timfennis Sep 2, 2026
5ccfadc
refactor(analyser): render type-annotation help as a note 📝
timfennis Sep 2, 2026
3fb7cc5
fix(parser): disambiguate cast comparisons 🧭
timfennis Sep 2, 2026
34a672a
fix(vm): bound cast error type rendering ⏱️
timfennis Sep 2, 2026
26b15dd
fix(vm): deduplicate aliased cast checks 🔁
timfennis Sep 2, 2026
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2 changes: 1 addition & 1 deletion ext/andy-cpp/syntaxes/andy-cpp.tmLanguage.json
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Original file line number Diff line number Diff line change
Expand Up @@ -308,7 +308,7 @@
{
"comment": "other keywords",
"name": "keyword.other.andy-cpp",
"match": "\\b(in)\\b"
"match": "\\b(in|as)\\b"
}
]
},
Expand Down
29 changes: 23 additions & 6 deletions ext/tree-sitter-andy-cpp/grammar.js
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Expand Up @@ -8,8 +8,8 @@
*
* assignment < comma/sequence < or < and < not < range
* < comparison/in < spaceship < shift < | < ~ < &
* < + - ++ <> < * / \ % %% < ^ (right assoc) < unary ! - ~
* < postfix call/index/member
* < + - ++ <> < * / \ % %% < ^ (right assoc) < as cast
* < unary ! - ~ < postfix call/index/member
*/

/* eslint-disable arrow-parens */
Expand All @@ -33,8 +33,9 @@ const PREC = {
term: 13,
factor: 14,
exponent: 15,
unary: 16,
call: 17,
cast: 16,
unary: 17,
call: 18,
};

/** @param {RuleOrLiteral} rule */
Expand All @@ -59,6 +60,10 @@ module.exports = grammar({
conflicts: $ => [
[$._pattern, $._expression],
[$.if_expression, $.if_guard],
// `x as Int < 2` — a `<` after a cast type may open a type argument list
// or be a less-than operator. Both branches are explored; the dynamic
// precedence on `generic_type` picks the cast when either parse works.
[$._type, $.generic_type],
],

rules: {
Expand Down Expand Up @@ -151,13 +156,18 @@ module.exports = grammar({

type_identifier: $ => /[A-Za-z_][A-Za-z0-9_]*/,

generic_type: $ => seq(
// A `<` after a type name is ambiguous in a cast: it may open a type
// argument list or be a less-than operator. The conflict declared above
// makes the parser try both; this dynamic precedence prefers the type
// argument list whenever it parses, mirroring the recursive-descent
// parser in `ndc_parser/src/parser.rs`.
generic_type: $ => prec.dynamic(1, seq(
field('name', $.type_identifier),
'<',
commaSep($._type),
optional(','),
'>',
),
)),

tuple_type: $ => seq(
'(',
Expand Down Expand Up @@ -186,6 +196,7 @@ module.exports = grammar({
$._literal,
$.unary_expression,
$.not_expression,
$.cast_expression,
$.binary_expression,
$.range_expression,
$.assignment,
Expand Down Expand Up @@ -240,6 +251,12 @@ module.exports = grammar({
field('right', $._expression_or_sequence),
)),

cast_expression: $ => prec.left(PREC.cast, seq(
field('value', $._expression),
'as',
field('type', $._type),
)),

unary_expression: $ => prec(PREC.unary, seq(
field('operator', choice('!', '-', '~')),
field('operand', $._expression),
Expand Down
5 changes: 4 additions & 1 deletion ext/tree-sitter-andy-cpp/queries/highlights.scm
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Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,10 @@
(continue_expression)
] @keyword.control

"in" @keyword.operator
[
"in"
"as"
] @keyword.operator

[
"and"
Expand Down
175 changes: 108 additions & 67 deletions ext/tree-sitter-andy-cpp/src/grammar.json
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Original file line number Diff line number Diff line change
Expand Up @@ -520,70 +520,74 @@
"value": "[A-Za-z_][A-Za-z0-9_]*"
},
"generic_type": {
"type": "SEQ",
"members": [
{
"type": "FIELD",
"name": "name",
"content": {
"type": "SYMBOL",
"name": "type_identifier"
}
},
{
"type": "STRING",
"value": "<"
},
{
"type": "CHOICE",
"members": [
{
"type": "SEQ",
"members": [
{
"type": "SYMBOL",
"name": "_type"
},
{
"type": "REPEAT",
"content": {
"type": "SEQ",
"members": [
{
"type": "STRING",
"value": ","
},
{
"type": "SYMBOL",
"name": "_type"
}
]
}
}
]
},
{
"type": "BLANK"
}
]
},
{
"type": "CHOICE",
"members": [
{
"type": "STRING",
"value": ","
},
{
"type": "BLANK"
"type": "PREC_DYNAMIC",
"value": 1,
"content": {
"type": "SEQ",
"members": [
{
"type": "FIELD",
"name": "name",
"content": {
"type": "SYMBOL",
"name": "type_identifier"
}
]
},
{
"type": "STRING",
"value": ">"
}
]
},
{
"type": "STRING",
"value": "<"
},
{
"type": "CHOICE",
"members": [
{
"type": "SEQ",
"members": [
{
"type": "SYMBOL",
"name": "_type"
},
{
"type": "REPEAT",
"content": {
"type": "SEQ",
"members": [
{
"type": "STRING",
"value": ","
},
{
"type": "SYMBOL",
"name": "_type"
}
]
}
}
]
},
{
"type": "BLANK"
}
]
},
{
"type": "CHOICE",
"members": [
{
"type": "STRING",
"value": ","
},
{
"type": "BLANK"
}
]
},
{
"type": "STRING",
"value": ">"
}
]
}
},
"tuple_type": {
"type": "SEQ",
Expand Down Expand Up @@ -704,6 +708,10 @@
"type": "SYMBOL",
"name": "not_expression"
},
{
"type": "SYMBOL",
"name": "cast_expression"
},
{
"type": "SYMBOL",
"name": "binary_expression"
Expand Down Expand Up @@ -1030,9 +1038,38 @@
]
}
},
"cast_expression": {
"type": "PREC_LEFT",
"value": 16,
"content": {
"type": "SEQ",
"members": [
{
"type": "FIELD",
"name": "value",
"content": {
"type": "SYMBOL",
"name": "_expression"
}
},
{
"type": "STRING",
"value": "as"
},
{
"type": "FIELD",
"name": "type",
"content": {
"type": "SYMBOL",
"name": "_type"
}
}
]
}
},
"unary_expression": {
"type": "PREC",
"value": 16,
"value": 17,
"content": {
"type": "SEQ",
"members": [
Expand Down Expand Up @@ -1878,7 +1915,7 @@
},
"call": {
"type": "PREC",
"value": 17,
"value": 18,
"content": {
"type": "SEQ",
"members": [
Expand Down Expand Up @@ -1961,7 +1998,7 @@
},
"index": {
"type": "PREC",
"value": 17,
"value": 18,
"content": {
"type": "SEQ",
"members": [
Expand Down Expand Up @@ -1994,7 +2031,7 @@
},
"member_expression": {
"type": "PREC_RIGHT",
"value": 17,
"value": 18,
"content": {
"type": "SEQ",
"members": [
Expand Down Expand Up @@ -2820,6 +2857,10 @@
[
"if_expression",
"if_guard"
],
[
"_type",
"generic_type"
]
],
"precedences": [],
Expand Down
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