+ # Caret error.
+ s/^ *#error.*\n *\^\n//gm;
+ # Number of errors.
+ s/^1 error generated\.\n//gm;
+
+ # 2. Normalize the lines we kept.
+
+ # Remove column.
+ s/^([^:]+:\d+)[.:][^:]+:(.+)$/$][1:$][2/gm;
+ # Map all combinations of "error: " and "#error: " to "#error ".
+ s/^([^:]+:\d+):( |#error|error|:)+/$][1: #error /gm;