Get rid of unused variables in std/algorithm

.dscanner.ini

@@ -157,7 +157,7 @@ undocumented_declaration_check="-etc.c.curl,-etc.c.odbc.sql,-etc.c.odbc.sqlext,-
 ; Checks for unused labels
 unused_label_check="-std.conv,-std.format,-std.internal.math.biguintx86,-std.regex.internal.thompson,-std.signals,-std.uni"
 ; Checks for unused variables and function parameters
-unused_variable_check="-std.algorithm.comparison,-std.algorithm.mutation,-std.algorithm.searching,-std.algorithm.setops,-std.algorithm.sorting,-std.array,-std.bigint,-std.bitmanip,-std.complex,-std.concurrency,-std.container,-std.container.array,-std.container.dlist,-std.container.rbtree,-std.container.slist,-std.conv,-std.csv,-std.datetime,-std.datetime.date,-std.datetime.interval,-std.datetime.stopwatch,-std.datetime.systime,-std.datetime.timezone,-std.digest.crc,-std.digest,-std.digest.md,-std.digest.murmurhash,-std.digest.ripemd,-std.digest.sha,-std.encoding,-std.exception,-std.experimental.allocator,-std.experimental.allocator.building_blocks.affix_allocator,-std.experimental.allocator.building_blocks.bitmapped_block,-std.experimental.allocator.building_blocks.bucketizer,-std.experimental.allocator.building_blocks.kernighan_ritchie,-std.experimental.allocator.building_blocks.stats_collector,-std.experimental.allocator.common,-std.experimental.allocator.gc_allocator,-std.experimental.allocator.mallocator,-std.experimental.allocator.typed,-std.experimental.checkedint,-std.experimental.logger.core,-std.experimental.typecons,-std.file,-std.format,-std.functional,-std.getopt,-std.internal.cstring,-std.internal.digest.sha_SSSE3,-std.internal.math.biguintcore,-std.internal.math.biguintx86,-std.internal.math.errorfunction,-std.internal.scopebuffer,-std.internal.test.dummyrange,-std.json,-std.math,-std.meta,-std.mmfile,-std.net.curl,-std.numeric,-std.parallelism,-std.process,-std.random,-std.range,-std.range.interfaces,-std.range.primitives,-std.regex.internal.backtracking,-std.regex.internal.tests,-std.regex.internal.thompson,-std.signals,-std.socket,-std.stdio,-std.string,-std.traits,-std.typecons,-std.uni,-std.uri,-std.utf,-std.uuid,-std.variant,-std.windows.registry,-std.xml,-std.zip,-std.zlib"
+unused_variable_check="-std.algorithm.comparison,-std.array,-std.bigint,-std.bitmanip,-std.complex,-std.concurrency,-std.container,-std.container.array,-std.container.dlist,-std.container.rbtree,-std.container.slist,-std.conv,-std.csv,-std.datetime,-std.datetime.date,-std.datetime.interval,-std.datetime.stopwatch,-std.datetime.systime,-std.datetime.timezone,-std.digest.crc,-std.digest,-std.digest.md,-std.digest.murmurhash,-std.digest.ripemd,-std.digest.sha,-std.encoding,-std.exception,-std.experimental.allocator,-std.experimental.allocator.building_blocks.affix_allocator,-std.experimental.allocator.building_blocks.bitmapped_block,-std.experimental.allocator.building_blocks.bucketizer,-std.experimental.allocator.building_blocks.kernighan_ritchie,-std.experimental.allocator.building_blocks.stats_collector,-std.experimental.allocator.common,-std.experimental.allocator.gc_allocator,-std.experimental.allocator.mallocator,-std.experimental.allocator.typed,-std.experimental.checkedint,-std.experimental.logger.core,-std.experimental.typecons,-std.file,-std.format,-std.functional,-std.getopt,-std.internal.cstring,-std.internal.digest.sha_SSSE3,-std.internal.math.biguintcore,-std.internal.math.biguintx86,-std.internal.math.errorfunction,-std.internal.scopebuffer,-std.internal.test.dummyrange,-std.json,-std.math,-std.meta,-std.mmfile,-std.net.curl,-std.numeric,-std.parallelism,-std.process,-std.random,-std.range,-std.range.interfaces,-std.range.primitives,-std.regex.internal.backtracking,-std.regex.internal.tests,-std.regex.internal.thompson,-std.signals,-std.socket,-std.stdio,-std.string,-std.traits,-std.typecons,-std.uni,-std.uri,-std.utf,-std.uuid,-std.variant,-std.windows.registry,-std.xml,-std.zip,-std.zlib"
 ; Check for useless user defined initializers
 useless_initializer="+disabled"
 ;useless_initializer="-etc.c.odbc.sqlext,-etc.c.zlib,-std.algorithm.iteration,-std.algorithm.mutation,-std.algorithm.searching,-std.algorithm.setops,-std.algorithm.sorting,-std.array,-std.bigint,-std.bitmanip,-std.compiler,-std.container.array,-std.container.dlist,-std.container.rbtree,-std.conv,-std.csv,-std.datetime.systime,-std.digest.md,-std.digest.murmurhash,-std.digest.ripemd,-std.encoding,-std.exception,-std.experimental.allocator,-std.experimental.allocator.building_blocks.bitmapped_block,-std.experimental.allocator.building_blocks.free_tree,-std.experimental.allocator.building_blocks.kernighan_ritchie,-std.experimental.allocator.common,-std.experimental.allocator.mallocator,-std.experimental.logger.core,-std.experimental.logger.multilogger,-std.file,-std.format,-std.functional,-std.getopt,-std.internal.cstring,-std.internal.digest.sha_SSSE3,-std.internal.math.biguintcore,-std.internal.math.biguintnoasm,-std.internal.math.biguintx86,-std.internal.math.gammafunction,-std.internal.test.dummyrange,-std.json,-std.math,-std.net.curl,-std.numeric,-std.parallelism,-std.path,-std.process,-std.random,-std.range,-std.range.interfaces,-std.range.primitives,-std.regex,-std.regex.internal.backtracking,-std.regex.internal.generator,-std.regex.internal.ir,-std.regex.internal.kickstart,-std.regex.internal.parser,-std.regex.internal.tests,-std.regex.internal.thompson,-std.signals,-std.socket,-std.stdio,-std.string,-std.uni,-std.uri,-std.utf,-std.uuid,-std.variant,-std.windows.registry,-std.windows.syserror,-std.xml,-std.zip,-std.zlib"

std/algorithm/mutation.d

@@ -520,6 +520,7 @@ $(HTTP sgi.com/tech/stl/copy_backward.html, STL's copy_backward'):
             copy(arr1, arr2);
             return 35;
         }();
+        assert(v == 35);
     }
 }
 
@@ -605,8 +606,10 @@ if ((isInputRange!Range && is(typeof(range.front = value)) ||
 @nogc @safe unittest
 {
     const(char)[] chars;
+    assert(chars.length == 0);
     static assert(!__traits(compiles, fill(chars, 'c')));
     wstring wchars;
+    assert(wchars.length == 0);
     static assert(!__traits(compiles, fill(wchars, wchar('c'))));
 }
 
@@ -929,6 +932,8 @@ if (is(Range == char[]) || is(Range == wchar[]))
     assert(a[] == [char.init, char.init, char.init]);
     string s;
     assert(!__traits(compiles, s.initializeAll()));
+    assert(!__traits(compiles, s.initializeAll()));
+    assert(s.empty);
 
     //Note: Cannot call uninitializedFill on narrow strings
 
@@ -1169,11 +1174,15 @@ pure nothrow @safe @nogc unittest
 {
     struct S
     {
+        int a = 1;
         @disable this(this);
         ~this() pure nothrow @safe @nogc {}
     }
     S s1;
+    s1.a = 2;
     S s2 = move(s1);
+    assert(s1.a == 1);
+    assert(s2.a == 2);
 }
 
 private void trustedMoveImpl(T)(ref T source, ref T target) @trusted
@@ -1592,6 +1601,7 @@ pure nothrow @nogc @system unittest
     Foo[3] dst = void;
 
     auto res = moveEmplaceSome(src[], dst[]);
+    assert(res.length == 2);
 
     import std.algorithm.searching : all;
     assert(src[0 .. 3].all!(e => e._ptr is null));
@@ -2518,8 +2528,14 @@ if (isBlitAssignable!T && !is(typeof(lhs.proxySwap(rhs))))
     assert(s2.y == [ 1, 2 ]);
 
     // Immutables cannot be swapped:
-    immutable int imm1, imm2;
+    immutable int imm1 = 1, imm2 = 2;
     static assert(!__traits(compiles, swap(imm1, imm2)));
+
+    int c = imm1 + 0;
+    int d = imm2 + 0;
+    swap(c, d);
+    assert(c == 2);
+    assert(d == 1);
 }
 
 ///
@@ -2565,6 +2581,7 @@ if (isBlitAssignable!T && !is(typeof(lhs.proxySwap(rhs))))
 
     // Const types cannot be swapped.
     const NoCopy const1, const2;
+    assert(const1.n == 0 && const2.n == 0);
     static assert(!__traits(compiles, swap(const1, const2)));
 }
 
@@ -2598,9 +2615,14 @@ if (isBlitAssignable!T && !is(typeof(lhs.proxySwap(rhs))))
     struct S
     {
         const int i;
+        int i2 = 2;
+        int i3 = 3;
     }
     S s;
     static assert(!__traits(compiles, swap(s, s)));
+    swap(s.i2, s.i3);
+    assert(s.i2 == 3);
+    assert(s.i3 == 2);
 }
 
 @safe unittest
@@ -2616,6 +2638,7 @@ if (isBlitAssignable!T && !is(typeof(lhs.proxySwap(rhs))))
     // 12024
     import std.datetime;
     SysTime a, b;
+    swap(a, b);
 }
 
 @system unittest // 9975

std/algorithm/searching.d

@@ -1691,11 +1691,8 @@ if (isInputRange!InputRange &&
 
 @safe pure nothrow unittest
 {
-    int[] a1 = [1, 2, 3];
     assert(!find              ([1, 2, 3], 2).empty);
     assert(!find!((a,b)=>a == b)([1, 2, 3], 2).empty);
-    ubyte[] a2 = [1, 2, 3];
-    ubyte   b2 = 2;
     assert(!find              ([1, 2, 3], 2).empty);
     assert(!find!((a,b)=>a == b)([1, 2, 3], 2).empty);
 }
@@ -1707,21 +1704,13 @@ if (isInputRange!InputRange &&
     {
         foreach (E; AliasSeq!(char, wchar, dchar))
         {
-            R r1 = "hello world";
-            E e1 = 'w';
             assert(find              ("hello world", 'w') == "world");
             assert(find!((a,b)=>a == b)("hello world", 'w') == "world");
-            R r2 = "日c語";
-            E e2 = 'c';
             assert(find              ("日c語", 'c') == "c語");
             assert(find!((a,b)=>a == b)("日c語", 'c') == "c語");
-            R r3 = "0123456789";
-            E e3 = 'A';
             assert(find              ("0123456789", 'A').empty);
             static if (E.sizeof >= 2)
             {
-                R r4 = "hello world";
-                E e4 = 'w';
                 assert(find              ("日本語", '本') == "本語");
                 assert(find!((a,b)=>a == b)("日本語", '本') == "本語");
             }
@@ -1737,11 +1726,8 @@ if (isInputRange!InputRange &&
     static assert(find("日本語", '本') == "本語");
     static assert(find([1, 2, 3], 2)  == [2, 3]);
 
-    int[] a1 = [1, 2, 3];
     static assert(find              ([1, 2, 3], 2));
     static assert(find!((a,b)=>a == b)([1, 2, 3], 2));
-    ubyte[] a2 = [1, 2, 3];
-    ubyte   b2 = 2;
     static assert(find              ([1, 2, 3], 2));
     static assert(find!((a,b)=>a == b)([1, 2, 3], 2));
 }
@@ -2145,6 +2131,7 @@ if (isForwardRange!R1 && isForwardRange!R2
 
 @safe unittest
 {
+    import std.algorithm.comparison : equal;
     // @@@BUG@@@ removing static below makes unittest fail
     static struct BiRange
     {
@@ -2157,6 +2144,7 @@ if (isForwardRange!R1 && isForwardRange!R2
         void popBack() { return payload.popBack(); }
     }
     auto r = BiRange([1, 2, 3, 10, 11, 4]);
+    assert(equal(find(r, [10, 11]), [10, 11, 4]));
 }
 
 @safe unittest
@@ -2277,6 +2265,7 @@ private R1 simpleMindedFind(alias pred, R1, R2)(R1 haystack, scope R2 needle)
     // If issue 7992 occurs, this will throw an exception from calling
     // popFront() on an empty range.
     auto r = find(CustomString("a"), CustomString("b"));
+    assert(r.empty);
 }
 
 /**
@@ -4605,7 +4594,7 @@ if (isInputRange!Range)
 
 @safe unittest // Issue 13124
 {
-    import std.algorithm.comparison : among;
+    import std.algorithm.comparison : among, equal;
     auto s = "hello how\nare you";
-    s.until!(c => c.among!('\n', '\r'));
+    assert(equal(s.until!(c => c.among!('\n', '\r')), "hello how"));
 }

std/algorithm/setops.d

@@ -1412,6 +1412,8 @@ setSymmetricDifference(alias less = "a < b", R1, R2)
 
 @safe unittest // Issue 10460
 {
+    import std.algorithm.comparison : equal;
+
     int[] a = [1, 2];
     double[] b = [2.0, 3.0];
     int[] c = [2, 3];
@@ -1423,6 +1425,9 @@ setSymmetricDifference(alias less = "a < b", R1, R2)
     alias R2 = typeof(setSymmetricDifference(a, c));
     static assert(is(ElementType!R2 == int));
     static assert(hasLvalueElements!R2);
+
+    assert(equal(setSymmetricDifference(a, b), [1.0, 3.0]));
+    assert(equal(setSymmetricDifference(a, c), [1, 3]));
 }
 
 /++

std/algorithm/sorting.d

@@ -2823,6 +2823,7 @@ private template TimSortImpl(alias pred, R)
     testSort(seed);
 
     enum result = testSort(seed);
+    assert(result == true);
 }
 
 @safe unittest
@@ -3118,11 +3119,10 @@ if (isRandomAccessRange!(Range) && hasLength!Range && hasSlicing!Range)
         // Workaround for https://issues.dlang.org/show_bug.cgi?id=16528
         // Safety checks: enumerate all potentially unsafe generic primitives
         // then use a @trusted implementation.
-        auto b = binaryFun!less(r[0], r[r.length - 1]);
+        binaryFun!less(r[0], r[r.length - 1]);
         import std.algorithm.mutation : swapAt;
         r.swapAt(size_t(0), size_t(0));
-        auto len = r.length;
+        static assert(is(typeof(r.length) == size_t));
-        static assert(is(typeof(len) == size_t));
         pivotPartition!less(r, 0);
     }
     bool useSampling = true;