Building Java sources with Maven using org.eclipse.tycho:tycho-compiler-jdt:0.19.0 produces compiler warnings in a slightly different format than older versions:
The only difference is the specification of the location within the source file:
 vs. [13,0]
The leads to the problem that when using the "Java Compiler (Eclipse)" parser does not detect any warnings.
When using the "Java Compiler (javac)" parser instead, the warnings are detected but the message is not extracted.
I've already patched the parser and will submit a pull request soon.