• d-bugmail puremagic.com (35/35) Jul 20 2021 https://issues.dlang.org/show_bug.cgi?id=22133

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=22133

          Issue ID: 22133
           Summary: [REG2.097] Breaking change in DotTemplateExp type
                    semantics leading to e.g. isInputRange regression
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: kinke gmx.net

```
import std.range.primitives : isInputRange;

struct Slice
{
    bool empty() const;
    int front() const;
    void popFront()() // note: requires a mutable Slice
    {}
}

static assert(isInputRange!(      Slice) == true);
static assert(isInputRange!(const Slice) == false); // fails since v2.097
```

It boils down to both of the following assertions failing since v2.097:
```
enum isInputRange1(R) = is(typeof((R r) => r.popFront));
enum isInputRange2(R) = __traits(compiles, (R r) => r.popFront);
static assert(isInputRange1!(const Slice) == false);
static assert(isInputRange2!(const Slice) == false);
```

Regression introduced by https://github.com/dlang/dmd/pull/12294.

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