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Fix #368: generate proper expression for null-coalescing operators on nullable types#369

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metoule merged 1 commit intodynamicexpresso:masterfrom
metoule:fix_367
Oct 6, 2025
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Fix #368: generate proper expression for null-coalescing operators on nullable types#369
metoule merged 1 commit intodynamicexpresso:masterfrom
metoule:fix_367

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@metoule metoule commented Sep 6, 2025 •
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The expression we generate for the null-coalescing operator doesn't work for nullable types, because there's no comparison operator between a nullable type and an object:

const object nullConst = null;
int? MyVar = null;
return MyVar == nullConst ? 0 : MyVar; // <-- doesn't compile

This PR changes the generated expression for nullable types from expr == null ? exprRight : expr to expr.HasValue ? expr.Value : exprRight

Fix #368

@metoule metoule changed the title Fix 367: generate proper expression for null-coalescing operators on nullable types Fix #368: generate proper expression for null-coalescing operators on nullable types Sep 6, 2025
@metoule metoule marked this pull request as draft September 7, 2025 13:41
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metoule commented Sep 7, 2025

Back to draft, so that I can see how to handle the other binary operators.

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metoule commented Sep 8, 2025

After playing with sharplab, I discovered that for nullable types, the .NET compiler generates:

int? a;
int b = a ?? 10; // int b = a.GetValueOrDefault(10);
int? a;
bool b = a > 10; // bool b = (a.GetValueOrDefault() > 10) & a.HasValue

I'll update the PR to match this.

@metoule metoule mentioned this pull request Oct 2, 2025
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@metoule metoule marked this pull request as ready for review October 2, 2025 17:44
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metoule commented Oct 2, 2025

It's actually ready, the other binary operators are properly resolved (e.g. int? > int works as intended).

@metoule metoule merged commit 8825efb into dynamicexpresso:master Oct 6, 2025
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@metoule metoule deleted the fix_367 branch October 6, 2025 10:58
@dependabot dependabot bot mentioned this pull request Oct 27, 2025
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@davideicardi davideicardi davideicardi approved these changes

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Nullable variables (int?) cause error on evaluation when value is null

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