In order to avoid issuing diagnostics for compiler-generate code, we ignore the
syntax subtree rooted at an implicit node. This causes our algorithm to miss
user code wrapped in implicit nodes during desugaring. For example, expressions
in implicit returns from single-expression closures and trailing closures are
completely ignored right now.
This change fixes heproblem by introducing a simple change to the AST walker.
Instead of ignoring the entire implicit-node subtree, we only ignore the
implicit node but continue to descend into its children. This enables our
algorithm to access non-implicit (user code) nodes nested inside
implicit (compiler-generated) nodes.
This commit introduces a performance hint check that warns on the use of
existential any in variable declarations, function and closure parameters and
returns, and typealiases.
This check will run on each type-checked primary input of the current compilation and emit a warning diagnostic for all discovered occurences of this code pattern when the performance hint diagnostic is enabled
