[Issue 14534] New: Front-end should lower all non-scalar condition expressions

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14534

          Issue ID: 14534
           Summary: Front-end should lower all non-scalar condition
                    expressions
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nobody at puremagic.com
          Reporter: ibuclaw at gdcproject.org

Types in D2 that have a non-scalar representation, this involves:
 - Dynamic arrays { size_t length, void *ptr }
 - Delegates { void *object, void *funcptr }
 - Associative arrays { void *ptr }

Are silently allowed to pass through the front-end in checkToBoolean checks as
valid boolean values.

This means that type-strict backends (GDC, LDC) must do it's own special
lowering to ensure that the correct value is extracted and proper scalar ->
bool conversion is done.

This also means that dmd, gdc, and ldc may be each doing something different
when it comes to the following operations.

---
if (arr) { ... }  // Could be (arr.ptr != null) or (arr.ptr || arr.length)
if (dg)  { ... }  // Could be (dg.funcptr != null) or (dg.object || dg.funcptr)
if (aa)  { ... }  // arr.ptr != null
---

So I propose that the front-end should instead do this lowering so the
behaviour is 'precisely defined' and not up for interpretation of the backend
implementer.

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