Merge pull request #8691 from ntrel/return-type

More avoidance of std.traits.ReturnType
dlang · Feb 20, 2023 · c9d1bd5 · c9d1bd5
2 parents 0cec16a + 1c397ee
commit c9d1bd5
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Showing 2 changed files with 8 additions and 4 deletions.
diff --git a/std/range/primitives.d b/std/range/primitives.d
@@ -1674,8 +1674,8 @@ The following expression must be true for `hasSlicing` to be `true`:
 
 ----
     isForwardRange!R
-    && !isNarrowString!R
-    && is(ReturnType!((R r) => r[1 .. 1].length) == size_t)
+    && !(isAutodecodableString!R && !isAggregateType!R)
+    && is(typeof((R r) { return r[1 .. 1].length; } (R.init)) == size_t)
     && (is(typeof(lvalueOf!R[1 .. 1]) == R) || isInfinite!R)
     && (!is(typeof(lvalueOf!R[0 .. $])) || is(typeof(lvalueOf!R[0 .. $]) == R))
     && (!is(typeof(lvalueOf!R[0 .. $])) || isInfinite!R

diff --git a/std/traits.d b/std/traits.d
@@ -986,6 +986,10 @@ private template fqnType(T,
  * or a class with an `opCall`. Please note that $(D_KEYWORD ref)
  * is not part of a type, but the attribute of the function
  * (see template $(LREF functionAttributes)).
+ *
+ * $(NOTE To reduce template instantiations, consider instead using
+ * $(D typeof(() { return func(args); } ())) if the argument types are known or
+ * $(D static if (is(typeof(func) Ret == return))) if only that basic test is needed.)
  */
 template ReturnType(alias func)
 if (isCallable!func)
@@ -7969,15 +7973,15 @@ has both opApply and a range interface.
 */
 template ForeachType(T)
 {
-    alias ForeachType = ReturnType!(typeof(
+    alias ForeachType = typeof(
     (inout int x = 0)
     {
         foreach (elem; T.init)
         {
             return elem;
         }
         assert(0);
-    }));
+    }());
 }
 
 ///