Bug 18804 – std.algorithm.mutation.copy puts whole source range into target range when it should put elements

I wrote this script to check my csv file for me: void main() { int line = 1; try { File("in") .byChunk(0x1000) .joiner .map!(to!(immutable char)) .array .csvReader!(Tuple!(string, bool, string)) .map!(a => a[2].substitute(';', '\n').csvReader!(Tuple!(float, float, float)).array) .tee!(el => line++) .map!(tuples => tuples.map!(tup => tup[0] + tup[1] + tup[2]).sum) .copy(nullSink) ; writeln("No problems"); } catch (Exception e) { writeln("On line ", line, ": ", e); } readln; } It does not catch any errors reqardless whether there are, but replacing range.copy(nullSink) with range.each!writeln fixes that. It seems the optimizer has got a bit too eager here. Just because nullSink discards what it receives does not mean the range shouldn't be processed, if there may be side-effects.

Generally, please post complete code, including imports. Also include the contents of other files like "in". What happens here is that `copy` puts the range as a whole into the NullSink. This is not DMD optimizing anything out. Reduced test case: ---- import std.algorithm.mutation: copy; struct NullSink { void put(E)(E) {} } int line = 0; struct R { int front; @property bool empty() { return line == 1; } void popFront() { line = 1; } } void main() { R r; copy(r, NullSink()); assert(line == 1); /* fails; should pass */ } ---- Pull request to fix this: https://github.com/dlang/phobos/pull/6485

Already being fixed? Thanks! imports are, on top of file: import std.stdio, std.file, std.conv, std.algorithm, std.range, std.string, std.typecons, std.math, std.csv; A few examples of correct lines from "in": Kukat,Gif\Kukat\1_Tumma_patina\05_Ruusu_tu.gif,false,"0.07,0.18,0.0; 0.09,0.25,0.0" Kukat,Gif\Kukat\1_Tumma_patina\06_Ruusu_tu.gif,false,"0.07,0.19,0.0; 0.1,0.28,0.0" Kukat,Gif\Kukat\1_Tumma_patina\09_Ruusu_tu.gif,false,"0.1,0.4,0.0; 0.1,0.56,0.0" Kukat,Gif\Kukat\1_Tumma_patina\10_Ruusukoynnos_tu.gif,false,"0.1,0.375,0.0"

Commits pushed to master at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/19052b08de1e269bf7e8ad1fef89540a5427b5d7 fix issue 18804 - std.algorithm.mutation.copy puts whole source range into target range when it should put elements https://github.com/dlang/phobos/commit/1d70525d00ec2aa6dbbe2713531f6c9fc7e19abb Merge pull request #6485 from aG0aep6G/18804 fix issue 18804 - std.algorithm.mutation.copy puts whole source range… merged-on-behalf-of: Sebastian Wilzbach <[email protected]>