std.algorithm.searching: Fix a -dip1000 compilable issue

[carblue]

Eliminates an error from std.algorithm.searching (the remaining errors are from std.algorithm.comparison and std.uni):

make -f posix.mak std/algorithm/searching.test [-dip1000 for std.algorithm.searching.d (the posix.mak I'm using is master+ https://github.com//pull/6195] + -dip1000 for searching.d; master at Latest commit 4820a49)]:

std/algorithm/searching.d(2101): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2102): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2103): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2104): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2105): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2106): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2424): Error: @safe function std.algorithm.searching.__unittest_L2416_C7 cannot call @system function std.algorithm.searching.find!(string, binaryFun, string).find
std/algorithm/searching.d(2436): Error: @safe function std.algorithm.searching.__unittest_L2430_C7 cannot call @system function std.algorithm.searching.find!(int[], binaryFun, int[]).find
std/algorithm/searching.d(2437): Error: @safe function std.algorithm.searching.__unittest_L2430_C7 cannot call @system function std.algorithm.searching.find!(int[], binaryFun, int[]).find
std/algorithm/searching.d(2443): Error: @safe function std.algorithm.searching.__unittest_L2440_C7 cannot call @system function std.algorithm.searching.find!(string, binaryFun, string).find

PR applied and function
R1 find(alias pred = "a == b", R1, R2)(R1 haystack, scope R2 needle)
temporarily attributed @safe, results in:

std/algorithm/searching.d(1969): Error: scope variable needle assigned to non-scope parameter r2 calling std.algorithm.comparison.mismatch!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).mismatch
std/algorithm/searching.d(2101): Error: template instance `std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b"))` error instantiating
std/uni.d(2553): Error: reference to local variable __tmpfordtor1666 assigned to non-scope parameter this calling std.uni.InversionList!(GcPolicy).InversionList.byInterval
std/uni.d(1976): Error: template instance `std.uni.InversionList!(GcPolicy)` error instantiating

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[MartinNowak]

We should better leave this to inference as opHash or opEquals of the element type could possibly escape a reference to one of the keys of the occ hash table. Somewhat unlikely but still possible, e.g. some cache of expensive hashing.

[carblue]

This sounds like rejection of PR, thus I will close it

[carblue]

@MartinNowak PR reopened:
I didn't gratuitously add scope, because for the implicit this parameter, it doesn't get inferred currently, as this will show. Temporarily apply these changes:

diff --git a/std/algorithm/searching.d b/std/algorithm/searching.d
index 42e128f..084bfc0 100644
--- a/std/algorithm/searching.d
+++ b/std/algorithm/searching.d
@@ -360,7 +360,7 @@ public:
     }
 
     ///
-    Range beFound(Range haystack)
+    Range beFound(Range haystack) @safe
     {
         import std.algorithm.comparison : max;
 
@@ -1839,7 +1839,7 @@ if (isInputRange!InputRange)
 }
 
 /// ditto
-R1 find(alias pred = "a == b", R1, R2)(R1 haystack, scope R2 needle)
+R1 find(alias pred = "a == b", R1, R2)(R1 haystack, scope R2 needle) @safe
 if (isForwardRange!R1 && isForwardRange!R2
         && is(typeof(binaryFun!pred(haystack.front, needle.front)) : bool))
 {
@@ -2408,7 +2408,7 @@ if (Ranges.length > 1 && is(typeof(startsWith!pred(haystack, needles))))
  * such position exists, returns `haystack` advanced to termination).
  */
 RandomAccessRange find(RandomAccessRange, alias pred, InputRange)(
-    RandomAccessRange haystack, scope BoyerMooreFinder!(pred, InputRange) needle)
+    RandomAccessRange haystack, scope BoyerMooreFinder!(pred, InputRange) needle) @safe
 {
     return needle.beFound(haystack);
 }
diff --git a/std/range/package.d b/std/range/package.d
index b179f98..e1609cc 100644
--- a/std/range/package.d
+++ b/std/range/package.d
@@ -9715,7 +9715,7 @@ if (isInputRange!Range)
     {
         return predFun(rhs, lhs);
     }
-    private Range _input;
+    /*private*/ Range _input;
 
     // Undocummented because a clearer way to invoke is by calling
     // assumeSorted.

make -f posix.mak std/algorithm/searching.test (aa[std.algorithm.searching]=-dip1000 in #6278)
results in:
...

T=`mktemp -d /tmp/.dmd-run-test.XXXXXX` &&                                                              \
  (                                                                                                     \
    ../dmd/generated/linux/release/64/dmd -od$T -conf= -I../druntime/import  -w -de -dip25 -m64 -fPIC -transition=complex -O -release -dip1000  -main -unittest generated/linux/release/64/libphobos2.a -defaultlib= -debuglib= -L-ldl -cov -run std/algorithm/searching.d ;     \
    RET=$? ; rm -rf $T ; exit $RET                                                                   \
  )
std/algorithm/searching.d(1969): Error: scope variable needle assigned to non-scope parameter r2 calling std.algorithm.comparison.mismatch!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).mismatch
std/algorithm/searching.d(2101): Error: template instance `std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b"))` error instantiating
std/algorithm/searching.d(2413): Error: scope variable needle assigned to non-scope parameter this calling std.algorithm.searching.BoyerMooreFinder!(binaryFun, string).BoyerMooreFinder.beFound
std/algorithm/searching.d(2424): Error: template instance `std.algorithm.searching.find!(string, binaryFun, string)` error instantiating
std/algorithm/searching.d(2413): Error: scope variable needle assigned to non-scope parameter this calling std.algorithm.searching.BoyerMooreFinder!(binaryFun, int[]).BoyerMooreFinder.beFound
std/algorithm/searching.d(2436): Error: template instance `std.algorithm.searching.find!(int[], binaryFun, int[])` error instantiating
posix.mak:571: die Regel für Ziel „std/algorithm/searching.test“ scheiterte (the rule for target ... failed)

Thus, BoyerMooreFinder.beFound doesn't get its this parameter inferred scope.
And if You extend changes above to
Range beFound(Range haystack) scope @safe
the same is true (not inferred) for ptrdiff_t occurrence(ElementType!(Range) c):

std/algorithm/searching.d(379): Error: scope variable this assigned to non-scope parameter this calling std.algorithm.searching.BoyerMooreFinder!(binaryFun, string).BoyerMooreFinder.occurrence
std/algorithm/searching.d(1969): Error: scope variable needle assigned to non-scope parameter r2 calling std.algorithm.comparison.mismatch!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).mismatch
std/algorithm/searching.d(2101): Error: template instance `std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b"))` error instantiating
std/algorithm/searching.d(379): Error: scope variable this assigned to non-scope parameter this calling std.algorithm.searching.BoyerMooreFinder!(binaryFun, int[]).BoyerMooreFinder.occurrence
std/algorithm/searching.d(2436): Error: template instance `std.algorithm.searching.find!(int[], binaryFun, int[])` error instantiating
posix.mak:571: die Regel für Ziel „std/algorithm/searching.test“ scheiterte (the rule for target ... failed)

I'm about to push an update for this PR

[wilzbach]

Just a spontaneous idea: couldn't inout be modified to also infer scope?

[schveiguy]

No, inout converts implicitly to const, it could be legally escaped. It also could be new data from the heap if returned.

[carblue]

Since I opened this PR 12 days ago, the errors changed to these:
make -f posix.mak std/algorithm/searching.test (aa[std.algorithm.searching]=-dip1000 in #6278):
...

T=`mktemp -d /tmp/.dmd-run-test.XXXXXX` &&                                                              \
  (                                                                                                     \
    ../dmd/generated/linux/release/64/dmd -od$T -conf= -I../druntime/import  -w -de -dip25 -m64 -fPIC -transition=complex -O -release -dip1000  -main -unittest generated/linux/release/64/libphobos2.a -defaultlib= -debuglib= -L-ldl -cov -run std/algorithm/searching.d ;     \
    RET=$? ; rm -rf $T ; exit $RET                                                                   \
  )
std/algorithm/searching.d(2101): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2101): Error: struct `std.range.SortedRange!(int[], "a < b").SortedRange` member _input is not accessible from @safe code
std/algorithm/searching.d(2101): Error: struct `std.range.SortedRange!(int[], "a < b").SortedRange` member _input is not accessible from @safe code
std/algorithm/searching.d(2102): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2102): Error: struct `std.range.SortedRange!(int[], "a < b").SortedRange` member _input is not accessible from @safe code
std/algorithm/searching.d(2102): Error: struct `std.range.SortedRange!(int[], "a < b").SortedRange` member _input is not accessible from @safe code
std/algorithm/searching.d(2103): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2103): Error: struct `std.range.SortedRange!(int[], "a < b").SortedRange` member _input is not accessible from @safe code
std/algorithm/searching.d(2103): Error: struct `std.range.SortedRange!(int[], "a < b").SortedRange` member _input is not accessible from @safe code
std/algorithm/searching.d(2104): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2105): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2106): Error: @safe function std.algorithm.searching.__unittest_L2088_C7 cannot call @system function std.algorithm.searching.find!("a == b", SortedRange!(int[], "a < b"), SortedRange!(int[], "a < b")).find
std/algorithm/searching.d(2424): Error: @safe function std.algorithm.searching.__unittest_L2416_C7 cannot call @system function std.algorithm.searching.find!(string, binaryFun, string).find
std/algorithm/searching.d(2436): Error: @safe function std.algorithm.searching.__unittest_L2430_C7 cannot call @system function std.algorithm.searching.find!(int[], binaryFun, int[]).find
std/algorithm/searching.d(2437): Error: @safe function std.algorithm.searching.__unittest_L2430_C7 cannot call @system function std.algorithm.searching.find!(int[], binaryFun, int[]).find
std/algorithm/searching.d(2443): Error: @safe function std.algorithm.searching.__unittest_L2440_C7 cannot call @system function std.algorithm.searching.find!(string, binaryFun, string).find

The additional ones can be removed again by removing protection attribute private from:
std.range.package. struct SortedRange(Range, alias pred = "a < b"). private Range _input;
which is probably not the right direction to go

[WalterBright]

Since this is congruent with the D vision, I added the Vision label and this is a priority issue. https://wiki.dlang.org/Vision/2018H1

[WalterBright]

If it still compiles successfully and passes the test suite after adding scope, then the addition is good to go. If that does turn out to break things, then the test suite (at least) is inadequate.