Start handling pattern types at the HIR -> Ty conversion boundary

compiler/rustc_hir_analysis/src/errors/pattern_types.rs

@@ -0,0 +1,9 @@
+use rustc_macros::Diagnostic;
+use rustc_span::Span;
+
+#[derive(Diagnostic)]
+#[diag(hir_analysis_pattern_type_wild_pat)]
+pub struct WildPatTy {
+    #[primary_span]
+    pub span: Span,
+}