4841 – -inline wrecks certain nested structs causing error "*** is a nested function and cannot be accessed from ***"

This is a D2 program:
import std.algorithm: map;
import std.array: array;
void main() {
 int c;
 array(map!((x){return c;})([1]));
}
It works if you compile it with dmd 2.048 with:
dmd test.d
But if use inlining:
dmd -inline test.d
It doesn't compile and dmd returns:
test.d(5): Error: function D main is a nested function and cannot be accessed from array
I think this is a compiler bug because inlining should not affect the compilability of a program.

Original title: "An array()/map inlining problem"
Here's a simpler case that gives the same error message, only with -inline:
---
struct Struct4841(alias pred)
{
 this(int k) { }
}
void bug4841a() {
 Struct4841!( (t) { any_old_garbage;} )( 1 ); 
}
void bug4841b() {
 bug4841a();
}
---
This is a problem with delegates and alias templates. It's not a regression.
There also seems to be an accepts-invalid bug in this. You can put any old garbage inside the alias, which seems odd. And you cannot declare a variable of type Struct4841!( (t) { any_old_garbage;} ) --- it's rejected at the parsing stage.

I think the following test case also belongs to this issue:
R1 find(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle)
{
 return simpleMindedFind!pred(haystack, needle);
}
R1 simpleMindedFind(alias pred, R1, R2)(R1 haystack, R2 needle)
{
 bool haystackTooShort()
 {
 return true;
 }
 return haystack;
}
sizediff_t indexOf(Char1, Char2)(const(Char1)[] s, const(Char2)sub)
{
 const(Char1)[] balance = find!({})(s, sub);
 return -1;
}
string extStr;
void main()
{
	extStr.indexOf("bla");
}

*** Issue 4724 has been marked as a duplicate of this issue. ***

Further reduced shows neither constructor nor delegate is required.
struct Struct4841(alias pred)
{
 void unused_func();
}
void bug4841a() {
 int w;
 Struct4841!( w ) m; 
}
void bug4841b() {
 bug4841a();
}
----------------
The unused function is required only because it makes Struct4841 into a nested struct.
I think it is because moving a templated nested struct changes its type - the enclosing function is part of the mangled name, or something like that. It can't trivially be moved around.

Commit pushed to master at https://github.com/D-Programming-Language/dmd
https://github.com/D-Programming-Language/dmd/commit/7766bbd9857ab5ad5b1d5ff0444cb7088823a793
fix Issue 4841 - -inline wrecks nested struct with alias template parameter (An array()/map inlining problem)

I just tested the fix that was merged recently. It only fixes some cases such as Don's and Tass3r's. Bearophile's case is still broken, as is the case I reported in Bug 4724.

I believe this is the same as bug 5939.

(In reply to comment #7)
> I believe this is the same as bug 5939.
I don't think bug 5939 involves -inline, but this one definitely does. Unless there are plans to make compiler changes are to fix bug 5939, the inliner shouldn't be making this transformation.

See also Issue 7559 

Another example of this would be:
import std.string;
void main()
{
 auto str = new char[](5);
 assert(sformat(str, "%s", 42) == "42");
}
If you compile with -inline, it fails to compile with the latest master, giving
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2593): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2593): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2596): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2596): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2596): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2597): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2593): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2593): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2596): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2596): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2596): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2597): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2601): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char[]).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2601): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char[]).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2604): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char[]).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2604): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char[]).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2604): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char[]).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2605): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, char[]).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2601): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)[]).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2601): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)[]).put
/home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(2604): Error: function std.string.sformat!(char, int).sformat is a nested function and cannot be accessed from std.range.put!(Sink, const(char)[]).put

import std.array: array;
import std.algorithm: map;
void main() {
 int[] foo;
 auto r1 = map!(i => foo[0])([0]);
 auto r2 = array(r1);
}
Gives (dmd 2.063 alpha):
temp.d(5): Error: function D main is a nested function and cannot be accessed
from std.array.array!(MapResult!(__lambda2, int[])).array

*** Issue 9187 has been marked as a duplicate of this issue. ***

*** Issue 9996 has been marked as a duplicate of this issue. ***

*** Issue 7129 has been marked as a duplicate of this issue. ***

Currently failing tests:
1. From Description
---
import std.algorithm: map;
import std.array: array;
void main()
{
 int c;
 map!(x => c)([1]).array();
}
---
2. From Comment 10
---
import std.string;
void main()
{
 assert(new char[5].sformat("%s", 42) == "42");
}
---
3. From Issue 7129 Comment 4
---
auto fun()
{
 int i;
 struct Result
 {
 this(int u) {}
 auto bar() { i = 42; }
 }
 return Result();
}
void main()
{
 auto t = fun();
 t.bar();
}
---

As mixing -inline/non-inline modules may result in a wrong code because of Issue 9193 one can use "-inline" only for toy D projects.

(In reply to comment #16)
> As mixing -inline/non-inline modules may result in a wrong code because of
> Issue 9193 one can use "-inline" only for toy D projects.
If you believe that to be true, then I think you should raise the Importance of this issue to Major.

https://github.com/D-Programming-Language/dmd/pull/2329 

Commits pushed to master at https://github.com/D-Programming-Language/dmd
https://github.com/D-Programming-Language/dmd/commit/1fbbe5966e372abb20e70c4ac69ecfaeaa6db952
fix Issue 4841 - -inline wrecks certain nested structs causing error "*** is a nested function and cannot be accessed from ***"
https://github.com/D-Programming-Language/dmd/commit/c19b8a43f45da1347302d3b49a3d1b0b53997003
Merge pull request #2329 from 9rnsr/fix4841
Issue 4841 - -inline wrecks certain nested structs causing error "*** is a nested function and cannot be accessed from ***"

*** Issue 11210 has been marked as a duplicate of this issue. ***