Make exponentiation operator print with right associativity.

[IwanKaramazow]

Fixes #1676

The exponentiation operator should be printed with right associativity.

let foo = (100. /. 2.) ** 2. +. (200. /. 2.) ** 2.;
let foo = 100. /. 2. ** 2. +. (200. /. 2.) ** 2.;
let foo = 100. /. 2. ** 2. +. 200. /. 2. ** 2.;

now compiles into

Math.pow(100 / 2, 2) + Math.pow(200 / 2, 2);
100 / Math.pow(2, 2) + Math.pow(200 / 2, 2);
var foo = 100 / Math.pow(2, 2) + 200 / Math.pow(2, 2);

with bucklescript, which is the correct output.

[jordwalke]

Why was this not an issue before?
And to be clear, if you don't refmt there is no bug, correct?

[chenglou]

Seems introduced in v3.0.0. Printer issue only

[IwanKaramazow]

It's indeed printer only. Parser seems to parse with the correct precedence.
The parsetree looks the same, aside from a subtle difference between & .
But that might me from using different ocaml versions, I think. Can't re-compile reason 1 at the moment because opam...

/* input */
let foo = (100. /. 2.) ** 2. +. (200. /. 2.) ** 2.;

reason 1

[
  structure_item (test.re[1,0+0]..[1,0+51])
    Pstr_value Nonrec
    [
      <def>
        pattern (test.re[1,0+4]..[1,0+7])
          Ppat_var "foo" (test.re[1,0+4]..[1,0+7])
        expression (test.re[1,0+10]..[1,0+50])
          Pexp_apply
          expression ([0,0+-1]..[0,0+-1])
            Pexp_ident "+." ([0,0+-1]..[0,0+-1])
          [
            <arg>
            Nolabel
              expression (test.re[1,0+10]..[1,0+28])
                Pexp_apply
                expression ([0,0+-1]..[0,0+-1])
                  Pexp_ident "**" ([0,0+-1]..[0,0+-1])
                [
                  <arg>
                  Nolabel
                    expression (test.re[1,0+10]..[1,0+22])
                      Pexp_apply
                      expression ([0,0+-1]..[0,0+-1])
                        Pexp_ident "/." ([0,0+-1]..[0,0+-1])
                      [
                        <arg>
                        Nolabel
                          expression (test.re[1,0+11]..[1,0+15])
                            Pexp_constant PConst_float (100.,None)
                        <arg>
                        Nolabel
                          expression (test.re[1,0+19]..[1,0+21])
                            Pexp_constant PConst_float (2.,None)
                      ]
                  <arg>
                  Nolabel
                    expression (test.re[1,0+26]..[1,0+28])
                      Pexp_constant PConst_float (2.,None)
                ]
            <arg>
            Nolabel
              expression (test.re[1,0+32]..[1,0+50])
                Pexp_apply
                expression ([0,0+-1]..[0,0+-1])
                  Pexp_ident "**" ([0,0+-1]..[0,0+-1])
                [
                  <arg>
                  Nolabel
                    expression (test.re[1,0+32]..[1,0+44])
                      Pexp_apply
                      expression ([0,0+-1]..[0,0+-1])
                        Pexp_ident "/." ([0,0+-1]..[0,0+-1])
                      [
                        <arg>
                        Nolabel
                          expression (test.re[1,0+33]..[1,0+37])
                            Pexp_constant PConst_float (200.,None)
                        <arg>
                        Nolabel
                          expression (test.re[1,0+41]..[1,0+43])
                            Pexp_constant PConst_float (2.,None)
                      ]
                  <arg>
                  Nolabel
                    expression (test.re[1,0+48]..[1,0+50])
                      Pexp_constant PConst_float (2.,None)
                ]
          ]
    ]
]

reason 3

[
  structure_item (exp.re[1,0+0]..[1,0+51])
    Pstr_value Nonrec
    [
      <def>
        pattern (exp.re[1,0+4]..[1,0+7])
          Ppat_var "foo" (exp.re[1,0+4]..[1,0+7])
        expression (exp.re[1,0+10]..[1,0+50])
          Pexp_apply
          expression (exp.re[1,0+29]..[1,0+31])
            Pexp_ident "+." (exp.re[1,0+29]..[1,0+31])
          [
            <label> ""
              expression (exp.re[1,0+10]..[1,0+28])
                Pexp_apply
                expression (exp.re[1,0+23]..[1,0+25])
                  Pexp_ident "**" (exp.re[1,0+23]..[1,0+25])
                [
                  <label> ""
                    expression (exp.re[1,0+10]..[1,0+22])
                      Pexp_apply
                      expression (exp.re[1,0+16]..[1,0+18])
                        Pexp_ident "/." (exp.re[1,0+16]..[1,0+18])
                      [
                        <label> ""
                          expression (exp.re[1,0+11]..[1,0+15])
                            Pexp_constant Const_float 100.
                        <label> ""
                          expression (exp.re[1,0+19]..[1,0+21])
                            Pexp_constant Const_float 2.
                      ]
                  <label> ""
                    expression (exp.re[1,0+26]..[1,0+28])
                      Pexp_constant Const_float 2.
                ]
            <label> ""
              expression (exp.re[1,0+32]..[1,0+50])
                Pexp_apply
                expression (exp.re[1,0+45]..[1,0+47])
                  Pexp_ident "**" (exp.re[1,0+45]..[1,0+47])
                [
                  <label> ""
                    expression (exp.re[1,0+32]..[1,0+44])
                      Pexp_apply
                      expression (exp.re[1,0+38]..[1,0+40])
                        Pexp_ident "/." (exp.re[1,0+38]..[1,0+40])
                      [
                        <label> ""
                          expression (exp.re[1,0+33]..[1,0+37])
                            Pexp_constant Const_float 200.
                        <label> ""
                          expression (exp.re[1,0+41]..[1,0+43])
                            Pexp_constant Const_float 2.
                      ]
                  <label> ""
                    expression (exp.re[1,0+48]..[1,0+50])
                      Pexp_constant Const_float 2.
                ]
          ]
    ]
]

[chenglou]

Merging! Thanks