> This PR adds experimental support for type-class based operator resolution.
> This means that it is possible to define classes that "witness" some
> numerical type class, like so:
>
>
> record Box(int i) {
> __witness Integral<Box> INTEGRAL = ...
> }
>
>
> Then, we can start using `Box` in e.g. binary operations, like so:
>
>
> Box one = new Box(1);
> Box two = new Box(1);
> one + two // three
>
>
> In order to support type-class mediated operator resolution, we needed to add
> a new kind of operator helper in `Operators`. These new operator helpers (one
> for unary operators, one for binary operators) wrap some method in one of the
> standard numeric classes -- for instance, type class `+` is realized through
> `Numerical::add`, and so forth.
>
> There's a new kind of operator symbol, namely `TypeClassOperatorSymbol` which
> is used to store the type of the operation as well as the method symbol in
> charge of performing the operation.
>
> To resolve an operator, we basically have to prove that a witness for the
> corresponding class, parameterized by the operand type exists. E.g. in the
> above, we need to find a witness for `Numerical<Box>`.
>
> During lowering, we emit such witness, and call the correct operator method
> on it.
>
> Note that support for assignment operators is also provided -- `Lower`
> already has logic to lower some assignment operators into plain binary
> operations, so we just leverage that support to translate type-class based
> assignment ops.
Maurizio Cimadamore has updated the pull request incrementally with one
additional commit since the last revision:
Test cleanup
-------------
Changes:
- all: https://git.openjdk.org/valhalla/pull/1948/files
- new: https://git.openjdk.org/valhalla/pull/1948/files/6dedb1de..2b56b03d
Webrevs:
- full: https://webrevs.openjdk.org/?repo=valhalla&pr=1948&range=01
- incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1948&range=00-01
Stats: 51 lines in 1 file changed: 2 ins; 1 del; 48 mod
Patch: https://git.openjdk.org/valhalla/pull/1948.diff
Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1948/head:pull/1948
PR: https://git.openjdk.org/valhalla/pull/1948
