Make left hand side of -> parse as a tuple of arguments
#522
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This makes argument lists on the left hand side of `->` parse as tuples. In particular, this fixes a very inconsistent case where the left hand side previously parsed as a `K"block"`; we now have: * `(a;x=1)->b` ==> `(-> (tuple-p a (parameters (= x 1))) b` rather than `(block a (= x 1))` on the left hand side. In addition, the following forms are treated consistently * `a->b` ==> `(-> (tuple a) b)` * `(a)->b` ==> `(-> (tuple-p a) b)` * `(a,)->b` ==> `(-> (tuple-p-, a) b)` The upside of this is that expression processing of `->` syntax should be much easier. There's one aberrant case involving `where` which is particularly difficult and still not dealt with: `(x where T) -> b` does not parse as `(where (tuple x) T)` on the left hand side. However, `where` precedence involving `::` and `->` is already horribly broken and this syntax will always be awful to write unless we make breaking changes. So I'm too tempted to call this a lost cause for now 😬. Compatibility shims for converting the `SyntaxNode` form back to `Expr` in order to keep `Expr` stable are included. (At some point we should consider fixing this and deleting these shims because the new form is so much more consistent and would be reflected neatly into `Expr` form.)
Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #522 +/- ##
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+ Coverage 96.18% 96.19% +0.01%
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Files 13 13
Lines 4032 4071 +39
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+ Hits 3878 3916 +38
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This caused an error in RBNF.jl, see thautwarm/RBNF.jl#17 for a workaround. I guess this is #535. |
c42f
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Oct 17, 2025
…ax.jl#522) This makes argument lists on the left hand side of `->` parse as tuples. In particular, this fixes a very inconsistent case where the left hand side previously parsed as a `K"block"`; we now have: * `(a;x=1)->b` ==> `(-> (tuple-p a (parameters (= x 1))) b` rather than `(block a (= x 1))` on the left hand side. In addition, the following forms are treated consistently * `a->b` ==> `(-> (tuple a) b)` * `(a)->b` ==> `(-> (tuple-p a) b)` * `(a,)->b` ==> `(-> (tuple-p-, a) b)` The upside of this is that expression processing of `->` syntax should be much easier. There's one aberrant case involving `where` which is particularly difficult and still not dealt with: `(x where T) -> b` does not parse as `(where (tuple x) T)` on the left hand side. However, `where` precedence involving `::` and `->` is already horribly broken and this syntax will always be awful to write unless we make breaking changes. So I'm too tempted to call this a lost cause for now 😬. Compatibility shims for converting the `SyntaxNode` form back to `Expr` in order to keep `Expr` stable are included. (At some point we should consider fixing this and deleting these shims because the new form is so much more consistent and would be reflected neatly into `Expr` form.)
topolarity
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Nov 14, 2025
…ax.jl#522) This makes argument lists on the left hand side of `->` parse as tuples. In particular, this fixes a very inconsistent case where the left hand side previously parsed as a `K"block"`; we now have: * `(a;x=1)->b` ==> `(-> (tuple-p a (parameters (= x 1))) b` rather than `(block a (= x 1))` on the left hand side. In addition, the following forms are treated consistently * `a->b` ==> `(-> (tuple a) b)` * `(a)->b` ==> `(-> (tuple-p a) b)` * `(a,)->b` ==> `(-> (tuple-p-, a) b)` The upside of this is that expression processing of `->` syntax should be much easier. There's one aberrant case involving `where` which is particularly difficult and still not dealt with: `(x where T) -> b` does not parse as `(where (tuple x) T)` on the left hand side. However, `where` precedence involving `::` and `->` is already horribly broken and this syntax will always be awful to write unless we make breaking changes. So I'm too tempted to call this a lost cause for now 😬. Compatibility shims for converting the `SyntaxNode` form back to `Expr` in order to keep `Expr` stable are included. (At some point we should consider fixing this and deleting these shims because the new form is so much more consistent and would be reflected neatly into `Expr` form.)
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This makes argument lists on the left hand side of
->parse as tuples. In particular, this fixes a very inconsistent case where the left hand side previously parsed as aK"block"; we now have:(a;x=1)->b==>(-> (tuple-p a (parameters (= x 1))) brather than
(block a (= x 1))on the left hand side.In addition, the following forms are treated consistently
a->b==>(-> (tuple a) b)(a)->b==>(-> (tuple-p a) b)(a,)->b==>(-> (tuple-p-, a) b)The upside of this is that expression processing of
->syntax should be much easier.There's one aberrant case involving
wherewhich is particularly difficult and still not dealt with:(x where T) -> bdoes not parse as(where (tuple x) T)on the left hand side. However,whereprecedence involving::and->is already horribly broken and this syntax will always be awful to write unless we make breaking changes. So I'm too tempted to call this a lost cause for now 😬.Compatibility shims for converting the
SyntaxNodeform back toExprin order to keepExprstable are included. (At some point we should consider fixing this and deleting these shims because the new form is so much more consistent and would be reflected neatly intoExprform.)