http://d.puremagic.com/issues/show_bug.cgi?id=6230

           Summary: Member functions can no longer be weakly pure
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: blocker
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: kennytm@gmail.com


--- Comment #0 from kennytm@gmail.com 2011-06-30 08:39:36 PDT ---
(See http://lists.puremagic.com/pipermail/phobos/2011-June/005487.html and comments in Phobos commit 4f28d** for existing discussion.)

After DMD commit 84b4f* a member function can no longer be pure, claiming itself as a nested function. I believe this is a bug because the relevant DMD code

            Dsymbol *vparent = v->toParent2();
            for (Dsymbol *s = sc->func; s; s = s->toParent2())
            {
                if (s == vparent)
                    break;
                FuncDeclaration *ff = s->isFuncDeclaration();
                if (!ff)
                    break;
                if (ff->setImpure())
                {   error("pure nested function '%s' cannot access mutable data
'%s'",
                        ff->toChars(), v->toChars());
                    break;
                }
            }

cannot check the case when 'vparent' is an aggregrate. Nevertheless, this leads to commits d014a and 40def in druntime, and 4f28d in Phobos**, which probably means this bug is INVALID.

Test case:
-----------------------
struct S {
    int p;
    int q() const pure {    // <-- Error
        return p;
    }
}

class C {
    int p;
    int q() const pure {    // <-- Error
        return p;
    }
}

int q2(ref const S s) pure {    // <-- Currently OK
    return s.p;
}

int q3(ref const C c) pure {    // <-- Currently OK
    return c.p;
}
-----------------------
y.d(4): Error: pure nested function 'q' cannot access mutable data 'p'
y.d(11): Error: pure nested function 'q' cannot access mutable data 'p'
-----------------------

* https://github.com/D-Programming-Language/dmd/commit/84b4f
** https://github.com/D-Programming-Language/druntime/commit/d014a
   https://github.com/D-Programming-Language/druntime/commit/40def
   https://github.com/D-Programming-Language/phobos/commit/4f28d

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--- Comment #1 from kennytm@gmail.com 2011-06-30 09:50:12 PDT ---
One possible patch:



diff --git a/src/expression.c b/src/expression.c
index 57cdd61..71f6239 100644
--- a/src/expression.c
+++ b/src/expression.c
@@ -1366,17 +1366,23 @@ void Expression::checkPurity(Scope *sc, VarDeclaration
*v, Expression *ethis)
              * requiring each function in between to be impure.
              */
             Dsymbol *vparent = v->toParent2();
-            for (Dsymbol *s = sc->func; s; s = s->toParent2())
+            Dsymbol *s = sc->func, *snext = s->toParent2();
+            // Make sure we're really finding parent *functions*, not parent
+            // class.
+            if (vparent->isFuncDeclaration() || snext != vparent)
             {
-                if (s == vparent)
-                    break;
-                FuncDeclaration *ff = s->isFuncDeclaration();
-                if (!ff)
-                    break;
-                if (ff->setImpure())
-                {   error("pure nested function '%s' cannot access mutable
data '%s'",
-                        ff->toChars(), v->toChars());
-                    break;
+                for (; s; s = s->toParent2())
+                {
+                    if (s == vparent)
+                        break;
+                    FuncDeclaration *ff = s->isFuncDeclaration();
+                    if (!ff)
+                        break;
+                    if (ff->setImpure())
+                    {   error("pure nested function '%s' cannot access mutable
data '%s'",
+                            ff->toChars(), v->toChars());
+                        break;
+                    }
                 }
             }
         }
diff --git a/src/func.c b/src/func.c
index 9957d7f..1cccbed 100644
--- a/src/func.c
+++ b/src/func.c
@@ -2664,9 +2664,9 @@ enum PURE FuncDeclaration::isPure()
     TypeFunction *tf = (TypeFunction *)type;
     if (flags & FUNCFLAGpurityInprocess)
         setImpure();
-    enum PURE purity = tf->purity;
-    if (purity == PUREfwdref)
+    if (tf->purity == PUREfwdref)
         tf->purityLevel();
+    enum PURE purity = tf->purity;
     if (purity > PUREweak && needThis())
     {   // The attribute of the 'this' reference affects purity strength
         if (type->mod & (MODimmutable | MODwild))
@@ -2676,6 +2676,9 @@ enum PURE FuncDeclaration::isPure()
         else
             purity = PUREweak;
     }
+    tf->purity = purity;
+    // ^ This rely on the current situation that every FuncDeclaration has a
+    //   unique TypeFunction.
     return purity;
 }

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kennytm@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


--- Comment #2 from kennytm@gmail.com 2011-07-04 12:25:20 PDT ---
DMD pull #210.

https://github.com/D-Programming-Language/dmd/pull/210

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


--- Comment #3 from Walter Bright <bugzilla@digitalmars.com> 2011-07-06 20:34:27 PDT ---
https://github.com/D-Programming-Language/dmd/commit/47efdef731e2ed1333aeedc053d37adff4356585

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--- Comment #4 from Walter Bright <bugzilla@digitalmars.com> 2011-08-01 21:44:14 PDT ---
https://github.com/D-Programming-Language/dmd/commit/1dac08b77af2826996567f629acf7f43d724cd48

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