[Issue 6857] New: Precondition contract checks should be statically bound.

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=6857

           Summary: Precondition contract checks should be statically
                    bound.
           Product: D
           Version: D2
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: timon.gehr at gmx.ch


--- Comment #0 from timon.gehr at gmx.ch 2011-10-26 14:08:40 PDT ---
import std.stdio;

class A{
    void foo()in{writeln("A, in!");assert(false);}out{writeln("A,
out!");}body{}
}
class B:A{
    override void foo()in{writeln("B, in!");}out{writeln("B, out!");}body{}
}

void main(){
    A x = new B;
    x.foo(); // prints all four messages
}

It is an error for the caller of foo to rely on the widened interface of B,
because the static type of x is A. Therefore only the in-contract of A should
be checked. The way it is now, in contracts provide no means of reasoning about
the validity of the code if the dynamic type of some instance is unknown during
compilation.

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