When I compile the following, the line number for the error in the lambda body is left out of the error message.

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public class HiddenLine {

    void m(String s1) {}

    static class Nested {
        void m2(Number n) {
            Runnable r = () -> m(n);
        }
    }

}

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error: incompatible types: Number cannot be converted to String
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
1 error

I can get the desired information using -Xdiags:verbose:

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HiddenLine.java:7: error: method m in class HiddenLine cannot be applied to given types;
            Runnable r = () -> m(n);
                               ^
  required: String
  found: Number
  reason: argument mismatch; Number cannot be converted to String
1 error