• d-bugmail puremagic.com (65/65) Feb 26 2023 https://issues.dlang.org/show_bug.cgi?id=23747

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=23747

          Issue ID: 23747
           Summary: 'auto ref' function return signature does not flag
                    escaping a reference to local variable
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: minor
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: Michael.Shah tufts.edu

Per the spec on 'auto ref'
https://dlang.org/spec/function.html#auto-ref-functions, I am not seeing the
same behavior with 'auto ref' for flagging escaped local references as shown in
the section on ref-functions:
https://dlang.org/spec/function.html#ref-functions

```
// Tested on: 
// DMD64 D Compiler v2.102.1

import std.stdio;

// The compiler will correctly
// flag this as a local variable 'i' escaping. 
//ref int Func1(){
//    int i=1;
//    return i;
//}


// BUGGY Behavior
// 'i' should be inferred as an 'int, thus a
// 'ref int' return value same as above.
ref auto Func2(){
    int i=2;
    return i;
}

// BUGGY Behavior
// Same as above, with explicit return type
auto ref int Func3(){
    int i=3;
    return i;
}

// Correct behavior
// Compiler flags `p` escaping a reference to local variable
//ref int* Func4(){
//    int  i=4;
//    int* p = &i;
//    return p;
//}

// BUGGY  behavior
ref auto Func5(){
    int  i=4;
    int* p = &i;
    return p;
}

void main(){

    auto two     = Func2();
    writeln(two, ":", typeid(two));

    auto three  = Func3();
    writeln(three, ":", typeid(three));

    auto five = Func5();
    writeln(five, ":", typeid(five));

}
```

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