[stable] Fix silly dmd.parse regression

src/dmd/parse.d

@@ -239,15 +239,18 @@ bool writeMixin(const(char)[] s, ref Loc loc)
 
     // write by line to create consistent line endings
     size_t lastpos = 0;
-    foreach (i,c; s)
+    for (size_t i = 0; i < s.length; ++i)
     {
         // detect LF and CRLF
+        const c = s[i];
         if (c == '\n' || (c == '\r' && i+1 < s.length && s[i+1] == '\n'))
         {
             ob.writestring(s[lastpos .. i]);
             ob.writenl();
             global.params.mixinLines++;
-            lastpos = i + (c == '\r' ? 2 : 1);
+            if (c == '\r')
+                ++i;
+            lastpos = i + 1;
         }
     }
 

test/runnable/extra-files/mixin.d

@@ -2,8 +2,8 @@
 // https://issues.dlang.org/show_bug.cgi?id=12790
 string get()
 {
-    return
-    q{int x;
+    return "int x =\n        123;\r\n" ~
+    q{
         int y;
 
 

test/runnable/extra-files/mixin.mixin

@@ -1,5 +1,7 @@
 // expansion at runnable/extra-files/mixin.d(16)
-int x;
+int x =
+        123;
+
         int y;