[Issue 22903] New: IFTI for immediately-invoked lambda keeps qualifier for pointer/slice argument

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22903

          Issue ID: 22903
           Summary: IFTI for immediately-invoked lambda keeps qualifier
                    for pointer/slice argument
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: snarwin+bugzilla at gmail.com

As of DMD 2.099.0, the following program fails to compile:

---
const(int*) p;
static assert(is(typeof((x => x)(p)) == const(int)*));
---

The error message is:

---
onlineapp.d(2): Error: static assert:  `is(const(int*) == const(int)*)` is
false
---

According to the language spec for IFTI [1], "the deduced type for dynamic
array and pointer arguments has an unqualified head", so the type deduced for
`x` should be `const(int)*`, not `const(int*)`.

If the lambda is defined in a separate statement, the correct type is deduced:

---
const(int*) p;
alias id = x => x;
static assert(is(typeof(id(p)) == const(int)*)); // passes
---

[1]: https://dlang.org/spec/template.html#ifti

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