v: refactor $var to ${var} across entire repository

[revosw]

String interpolation has two supported variants as of today. $var and ${var}, with ${var} being preferred.

vfmt automatically converts $var to ${var}, but only for code that runs. Comments, .vsh files and test artifacts such as .vv, .out and such are unaffected. Refactoring all occurrences to the new format is a step in entirely removing the interpolation support for $var.

scanner.v has not been altered, a follow-up commit that actually removes support for $var can do the final work in rephrasing comments and such.

Other notes:

str.v:348 | Need to rephrase comment regarding interpolation
syntax.v_:306 | Not sure what effect changing $literal to ${literal} has here, didn't touch

[revosw]

If I understand the vlib/v/slow_tests/inout/panic_array_decompose_extra_args.vv failure correctly, I should change array := ... from:

fn main() {
  array := ['a', 'b', 'c']

  print_1(array[0])

  print_1(...array)
  print_2(...array)
  print_3(...array)

  print_1(...array[1..2])
  print_2(...array[1..])

  println('================ V panic ================')
  print_4(...array)
}

To:

fn main() {
  array := ['\${a}', '\${b}', '\${c}']

  print_1(array[0])

  print_1(...array)
  print_2(...array)
  print_3(...array)

  print_1(...array[1..2])
  print_2(...array[1..])

  println('================ V panic ================')
  print_4(...array)
}

[revosw]

There is also other output that is misaligned, for example the ~~~~ in this check

Error: vlib/v/scanner/tests/undefined_ident_in_string_literal_err.vv:2:16: error: expression does not return a value
    1 | fn abc() string {
    2 |     return 'abc ${type}'
      |                   ~~~~
    3 | }
    4 |
============

diff: 
@@ -1,13 +1,13 @@
Error: -vlib/v/scanner/tests/undefined_ident_in_string_literal_err.vv:2:15: error: undefined ident: `type`
-    1 | fn abc() string {
-    2 |     return 'abc ${type}'
-      |                  ~~~~
-    3 | }
-    4 |
Error: -vlib/v/scanner/tests/undefined_ident_in_string_literal_err.vv:2:15: error: expression does not return a value
-    1 | fn abc() string {
-    2 |     return 'abc ${type}'
-      |                  ~~~~
Error: +vlib/v/scanner/tests/undefined_ident_in_string_literal_err.vv:2:16: error: undefined ident: `type`
+    1 | fn abc() string {
+    2 |     return 'abc ${type}'
+      |                   ~~~~
+    3 | }
+    4 |
Error: +vlib/v/scanner/tests/undefined_ident_in_string_literal_err.vv:2:16: error: expression does not return a value
+    1 | fn abc() string {
+    2 |     return 'abc ${type}'
+      |                   ~~~~
    3 | }
    4 |

I should run v test-all locally and fix the ones that are obvious from my changes

[JalonSolov]

If I understand the vlib/v/slow_tests/inout/panic_array_decompose_extra_args.vv failure correctly, I should change array := ... from:

fn main() {
  array := ['a', 'b', 'c']

  print_1(array[0])

  print_1(...array)
  print_2(...array)
  print_3(...array)

  print_1(...array[1..2])
  print_2(...array[1..])

  println('================ V panic ================')
  print_4(...array)
}

To:

fn main() {
  array := ['\${a}', '\${b}', '\${c}']

  print_1(array[0])

  print_1(...array)
  print_2(...array)
  print_3(...array)

  print_1(...array[1..2])
  print_2(...array[1..])

  println('================ V panic ================')
  print_4(...array)
}

No, this is incorrect. There are no variables by those names, and no $ in front of them in the current strings, so that bit should not be modified at all.

[revosw]

I'll consolidate the errors in this one message.

• vlib\v\checker\tests\prefix_err.out

I have mistakenly changed the error message from error: cannot take the address of '$b' to error: cannot take the address of '${b}'.

vlib/v/checker/tests/prefix_err.vv:11:6: error: cannot take the address of '${b}'
    9 | _ := &10
   10 | _ := &'Hi'
   11 | _ := &'${b}'
      |      ^
   12 | _ := &`c`
   13 | _ := &1.2

My guess is that it's because ast.StringInterLiteral uses a str() that outputs the contents of the string interpolation, not including ${ and }. But I haven't looked deep into it.

fn (mut c Checker) prefix_expr(mut node ast.PrefixExpr) ast.Type {

	// ...

	if node.op == .amp && (!right_is_ptr || (right_is_ptr && expr is ast.CallExpr)) {
		if expr in [ast.BoolLiteral, ast.CallExpr, ast.CharLiteral, ast.FloatLiteral, ast.IntegerLiteral,
			ast.InfixExpr, ast.StringLiteral, ast.StringInterLiteral] {
			c.error('cannot take the address of ${expr}', node.pos)
		}

		// ...
	}
}

• vlib/v/slow_tests/inout/comptime_smartcast_variant.vv
  Exactly the same behavior as prefix_err.out. The checker outputs the interpolation as $var instead of ${var}

I was going to write out all of the tests, but I would just be repeating myself. Should I change all my .out files to simply contain $var, or is it desirable that the string representation of a string interpolation is changed to the ${var} form?

[JalonSolov]

${var} is the correct form in all string interpolation cases. If you want to print the actual characters, \${var} should work... if it doesn't, it's a bug.

[revosw]

I am very pleased to say that I consider this pull request ready for proper review after CI has finished.

In the commit "ast: always output string literals with braces", I took the liberty to refactor get_fspec_braces (now called get_fspec) and their call sites to completely remove needs_braces and the conditional branching related to it. Now it always output braces.

[spytheman]

Excellent work.
Thank you @revosw 🙇🏻 for the patience and perseverance .