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Issue 6418 - [CTFE] Cannot call a struct member function with name 'length'.
Summary: [CTFE] Cannot call a struct member function with name 'length'.
Status: RESOLVED FIXED
Alias: None
Product: D
Classification: Unclassified
Component: dmd (show other issues)
Version: D2
Hardware: Other All
: P2 major
Assignee: No Owner
URL:
Keywords: ice-on-valid-code, rejects-valid
Depends on:
Blocks:
 
Reported: 2011-07-31 11:16 UTC by Dmitry Olshansky
Modified: 2011-08-03 17:15 UTC (History)
3 users (show)

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Description Dmitry Olshansky 2011-07-31 11:16:16 UTC 
Test case:

import std.range;

enum table = [2, 3, 5, 7, 11];

uint lookup(uint k)
{
        auto tab = assumeSorted(table);
        tab.equalRange(k);  //changing it to lowerBound works
        assert(!tab.empty);
        return 42;
}
enum t = lookup(7);

invking dmd:
dmd2/linux/bin/../../src/phobos/std/range.d(5572): Error: cannot evaluate this.length() at compile time
dmd2/linux/bin/../../src/phobos/std/range.d(5620): Error: cannot evaluate this.getTransitionIndex(v) at compile time
dmd2/linux/bin/../../src/phobos/std/range.d(5620): Error: cannot evaluate this.opSlice(0LU,this.getTransitionIndex(v)) at compile time
dmd2/linux/bin/../../src/phobos/std/range.d(5693): Error: cannot evaluate this.opSlice(first,it).lowerBound(value) at compile time
Segmentation fault (core dumped)
Comment 1 kennytm 2011-07-31 15:17:29 UTC 
Reduced test case (which doesn't trigger the ICE, but should have the same cause):

---------------------
struct Bug6418 {
    size_t length2() { return 1; } 
    size_t length() { return 1; }
}
static assert(Bug6418.init.length2 == 1);  // <-- ok
static assert(Bug6418.init.length == 1);   // <-- error
---------------------
x.d(6): Error: cannot evaluate Bug6418().length() at compile time
x.d(6): Error: static assert  (Bug6418().length() == 1u) is not evaluatable at compile time
---------------------


Temporary workaround to Phobos is to change all 'length' to '_input.length':

diff --git a/std/range.d b/std/range.d
index 622f7b8..a8e4e4e 100644
--- a/std/range.d
+++ b/std/range.d
@@ -5618,7 +5618,7 @@ if (isRandomAccessRange!Range)
     private size_t getTransitionIndex(SearchPolicy sp, alias test, V)(V v)
     if (sp == SearchPolicy.trotBackwards || sp == SearchPolicy.gallopBackwards)
     {
-        immutable count = length;
+        immutable count = _input.length;
         if (empty || !test(back, v)) return count;
         if (count == 1) return 0;
         size_t below = count - 2, above = count - 1, step = 2;
@@ -5690,7 +5690,7 @@ if (isRandomAccessRange!Range)
     if (is(V : ElementType!Range))
     {
         ElementType!Range v = value;
-        return this[getTransitionIndex!(sp, gt)(v) .. length];
+        return this[getTransitionIndex!(sp, gt)(v) .. _input.length];
     }
 
 // equalRange
@@ -5739,12 +5739,12 @@ if (isRandomAccessRange!Range)
                 // Gallop towards the left end as it's likely nearby
                 immutable left = first
                     + this[first .. it]
-                    .lowerBound!(SearchPolicy.gallopBackwards)(value).length;
+                    .lowerBound!(SearchPolicy.gallopBackwards)(value)._input.length;
                 first += count;
                 // Gallop towards the right end as it's likely nearby
                 immutable right = first
                     - this[it + 1 .. first]
-                    .upperBound!(SearchPolicy.gallop)(value).length;
+                    .upperBound!(SearchPolicy.gallop)(value)._input.length;
                 return this[left .. right];
             }
         }
Comment 2 Don 2011-07-31 21:41:04 UTC 
There are two bugs here. The segfault has a completely different cause from the rejects-valid bug.