Add SplicePattern AST to parse and type quote pattern splices #17396
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nicolasstucki
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| @@ -1566,6 +1587,8 @@ object Trees { | |||
| cpy.Quote(tree)(transform(body)(using quoteContext), transform(tags)) | |||
| case tree @ Splice(expr) => | |||
| cpy.Splice(tree)(transform(expr)(using spliceContext)) | |||
| case tree @ SplicePattern(body, args) => | |||
| cpy.SplicePattern(tree)(transform(body)(using spliceContext), transform(args)) | |||
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Why isn't spliceContext used for the arguments?
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Arguments of the SplicePattern are defined and references within the quoted pattern. The definition and references are at the same level.
case '{ (x: T) => $f(x) } =>In this example f is the body, which is at a lower staging level and usable in the RHS of the =>. On the other hand x is defined in the pattern (x: T) and then referenced in the pattern within the SplicePattern in (x).
| record("typedSplicePattern") | ||
| if (isFullyDefined(pt, ForceDegree.flipBottom)) { | ||
| def spliceOwner(ctx: Context): Symbol = | ||
| if (ctx.mode.is(Mode.QuotedPattern)) spliceOwner(ctx.outer) else ctx.owner |
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Aren't we always in mode QuotedPattern here?
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Only in the first iteration. We want to find the first context that is outside of the quote pattern. Note the recursion spliceOwner(ctx.outer) and the end ctx.owner. I will refactor it to make this clearer.
| val pat = typedPattern(tree.body, defn.QuotedExprClass.typeRef.appliedTo(patType))( | ||
| using spliceContext.retractMode(Mode.QuotedPattern).addMode(Mode.Pattern).withOwner(spliceOwner(ctx))) | ||
| val baseType = pat.tpe.baseType(defn.QuotedExprClass) | ||
| val argType = if baseType != NoType then baseType.argTypesHi.head else defn.NothingType |
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| val argType = if baseType != NoType then baseType.argTypesHi.head else defn.NothingType | |
| val argType = if baseType.exists then baseType.argTypesHi.head else defn.NothingType |
| report.error(em"Type must be fully defined.\nConsider annotating the splice using a type ascription:\n ($tree: XYZ).", tree.body.srcPos) | ||
| tree.withType(UnspecifiedErrorType) |
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We usually use errorTree(tree, ...) for this
| * Parser will only create `${ pattern }` and `$ident`, hence they will not have args. | ||
| * While typing, the `$ident(args*)` the args are identified and desugared into a `SplicePattern` | ||
| * containing them. |
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Why not have the parser take care of this since it's based purely on syntactic information?
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In the next PR I will introduce QuotePattern. At that point SplicePatterns will be kept after parser and until we encode the pattern into unapply and '{..}s.
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Splices in quoted expressions and quoted patterns are fundamentally different. SplicePattern makes this difference explicit and also handles HOAS arguments to the pattern splices.