transformer: fix precalculations of simple expressions involving floating literals, with -prod (fix VSL tests with -prod)

vlib/v/tests/prod/f64_literals_and_simple_expressions_should_not_round_as_f32.prod.v

@@ -0,0 +1,30 @@
+import math
+
+struct Sample {
+	value   f64
+	literal f64
+}
+
+fn s(literal f64, value f64) Sample {
+	return Sample{value, literal}
+}
+
+fn main() {
+	mut samples := [
+		s(1.0000000000000000, 1_000_000.0 * 10.0 / 10_000_000.0),
+		s(0.3333333333333300, 1.0 / 3.0),
+		s(2.5000000000000000, 10 / 4.0),
+		s(0.6666666666666600, 2.0 / 3.0),
+		s(0.1000000000000000, 1 / 10.0),
+		s(3.1415926535897932, math.pi),
+	]
+	mut fails := 0
+	for sample in samples {
+		equal := math.abs(sample.value - sample.literal) < 0.00000000001
+		eprintln('> sample.value: ${sample.value:20.16f} | sample.literal: ${sample.literal:20.16f} | equal: $equal')
+		if !equal {
+			fails++
+		}
+	}
+	eprintln('> FAILS: $fails .')
+}

vlib/v/tests/prod/f64_literals_and_simple_expressions_should_not_round_as_f32.prod.v.expected.txt

@@ -0,0 +1,7 @@
+> sample.value:   1.0000000000000000 | sample.literal:   1.0000000000000000 | equal: true
+> sample.value:   0.3333333333333333 | sample.literal:   0.3333333333333300 | equal: true
+> sample.value:   2.5000000000000000 | sample.literal:   2.5000000000000000 | equal: true
+> sample.value:   0.6666666666666666 | sample.literal:   0.6666666666666600 | equal: true
+> sample.value:   0.1000000000000000 | sample.literal:   0.1000000000000000 | equal: true
+> sample.value:   3.1415926535897930 | sample.literal:   3.1415926535897930 | equal: true
+> FAILS: 0 .

vlib/v/transformer/transformer.v

@@ -866,8 +866,8 @@ pub fn (mut t Transformer) infix_expr(mut node ast.InfixExpr) ast.Expr {
 			ast.FloatLiteral {
 				match mut node.right {
 					ast.FloatLiteral {
-						left_val := node.left.val.f32()
+						left_val := node.left.val.f64()
-						right_val := node.right.val.f32()
+						right_val := node.right.val.f64()
 						match node.op {
 							.eq {
 								return ast.BoolLiteral{