[Issue 21312] New: [REG 2.095] Newly triggered <expr> is not an lvalue and cannot be modified

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21312

          Issue ID: 21312
           Summary: [REG 2.095] Newly triggered <expr> is not an lvalue
                    and cannot be modified
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: industry, rejects-valid
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: pro.mathias.lang at gmail.com

Test code:
```
public T deserializeFull (T) () @safe
{
    static if (is(T : E*, E))
    {
        return &[ deserializeFull!(typeof(T.init[0]))() ][0];
    }
    return T.init;
}

struct Block { string value; }

void main ()
{
    auto b = deserializeFull!(immutable(Block)*)();
}
```

Works in v2.094.0, but with master, breaks with:
```
foo.d(5): Error: [deserializeFull()][0] is not an lvalue and cannot be modified
foo.d(14): Error: template instance foo.deserializeFull!(immutable(Block)*)
error instantiating
```

Introduced by https://github.com/dlang/dmd/pull/10124

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