Merge remote-tracking branch 'upstream/stable' into merge_stable

std/regex/internal/tests.d

@@ -1106,3 +1106,15 @@ alias Sequence(int B, int E) = staticIota!(B, E);
     auto e = collectException!RegexException(regex(q"<[^]>"));
     assert(e.msg.canFind("no operand for '^'"), e.msg);
 }
+
+// bugzilla 17673
+@safe unittest
+{
+    string str = `<">`;
+    string[] regexps = ["abc", "\"|x"];
+    auto regexp = regex(regexps);
+    auto c = matchFirst(str, regexp);
+    assert(c);
+    assert(c.whichPattern == 2);
+}
+

std/regex/package.d

@@ -374,9 +374,15 @@ if (isSomeString!(S))
                 app.put("|");
             app.put("(?:");
             app.put(patterns[i]);
+            // terminator for the pattern
+            // to detect if the pattern unexpectedly ends
             app.put("\\");
-            app.put(cast(dchar)(privateUseStart+i)); // special end marker
+            app.put(cast(dchar)(privateUseStart+i));
             app.put(")");
+            // another one to return correct whichPattern
+            // for all of potential alternatives in the patterns[i]
+            app.put("\\");
+            app.put(cast(dchar)(privateUseStart+i));
         }
         pat = app.data;
     }