[Rafael-SOWNet]

Fixes #2222.

Over System.Numerics.Complex, in FastExpression and in the LINQ compiler, a product's imaginary part is a.Re b.Im + a.Im b.Re. With a real infinity that is ∞ · 0, which is NaN. So -x at +oo was (-∞, NaN), and so were 2 * x, x / 2 and x * x. That is a value with no imaginary part at all: a comparison of it had no truth value, and a piecewise passed over it. Evaluation gives -oo, and so does the compiler over double.

RealProducts.Product and RealProducts.Quotient take two numbers whose imaginary parts are both 0 as reals, and anything else as before. FastExpression's CALL_MUL and CALL_DIV call them, and so do the LINQ compiler's Multiply and Divide over Complex.

A division by 0 is left to Complex, whose NaN is evaluation's. A real quotient would have made 1/x at 0 equal +∞, where evaluation has no value for 1/0.

	2.6.0 and master	now
"-x".ToEntity().Compile("x").Call(double.PositiveInfinity)	(-Infinity, NaN)	(-Infinity, 0)
"x / 2".ToEntity().Compile<Complex, Complex>("x")(double.PositiveInfinity)	(Infinity, NaN)	(Infinity, 0)

#2223's MembershipCompilationTest kept its piecewise case away from the infinities because of this. That case now runs at +oo and -oo too.

Tests: RealProductCompilationTest has 8 expressions at +oo or -oo, all failing on master. It also has 6 cases elsewhere that keep their values: a division by 0, and complex products and quotients. Full suite 18025/0, interactive trio, AOT smoke 73/0, all frameworks build.

A power at a real infinity comes out NaN in both parts. That is a different mechanism, Complex.Pow, filed as #2225.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.66%. Comparing base (5c6a13f) to head (4b17696).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2226      +/-   ##
==========================================
- Coverage   86.67%   86.66%   -0.02%     
==========================================
  Files         308      309       +1     
  Lines       67639    67644       +5     
  Branches    19610    19612       +2     
==========================================
- Hits        58628    58625       -3     
- Misses       4895     4899       +4     
- Partials     4116     4120       +4     

Flag	Coverage Δ
cpp	37.77% <ø> (ø)
csharp	87.21% <100.00%> (-0.02%)	⬇️
fsharp	32.97% <ø> (ø)
interactive	40.72% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ath/Functions/Compilation/IntoFE/FastExpression.cs	96.72% <100.00%> (ø)
...ctions/Compilation/IntoLinq/CompilationProtocol.cs	91.36% <100.00%> (+0.06%)	⬆️
.../AngouriMath/Functions/Compilation/RealProducts.cs	100.00% <100.00%> (ø)

... and 10 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.