Unnecessarily multiline squiggles on function definitions distracting.

[polypus74]

Certain errors/warnings draw squiggles underneath entire function definitions. This is visually distracting, especially with very large function definitions. Either only the function name, or first line should be squiggled, imo. Note in the attached picture that if an fn has a single line of arguments without a where clause then only the first line is squiggled. Functions with where clauses on a separate line (not sure about on same line as args because rustfmt always indents them as shown anyways), or with multiline arguments always get fully "squiggled".