Merge #5732

5732: Consider only IdentPats for param name hints r=matklad a=SomeoneToIgnore

Closes https://github.com/rust-analyzer/rust-analyzer/issues/4960

Avoid displaying any param name hints like 
<img width="590" alt="image" src="https://user-images.githubusercontent.com/2690773/90071461-47a4ad80-dcfe-11ea-9330-fb4f4e2d1b71.png">

Those hints seem to occupy plenty of space for no apparent benefit, with their destructured content not used in the code with the function hints.

I'm not entirely sure if we should show something else than `IdentPat`s, since I don't understand some of the `Pat` variant meanings:
https://github.com/rust-analyzer/rust-analyzer/blob/a1c187eef3ba08076aedb5154929f7eda8d1b424/crates/syntax/src/ast/generated/nodes.rs#L1336-L1352

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>

crates/ra_ide/src/inlay_hints.rs

@@ -156,15 +156,15 @@ fn get_param_name_hints(
         .params(sema.db)
         .into_iter()
         .zip(args)
-        .filter_map(|((param, _ty), arg)| match param? {
-            Either::Left(self_param) => Some((self_param.to_string(), arg)),
-            Either::Right(pat) => {
-                let param_name = match pat {
+        .filter_map(|((param, _ty), arg)| {
+            let param_name = match param? {
+                Either::Left(self_param) => self_param.to_string(),
+                Either::Right(pat) => match pat {
                     ast::Pat::IdentPat(it) => it.name()?.to_string(),
-                    it => it.to_string(),
-                };
-                Some((param_name, arg))
-            }
+                    _ => return None,
+                },
+            };
+            Some((param_name, arg))
         })
         .filter(|(param_name, arg)| should_show_param_name_hint(sema, &callable, &param_name, &arg))
         .map(|(param_name, arg)| InlayHint {
@@ -707,6 +707,8 @@ fn different_order(param: &Param) {}
 fn different_order_mut(param: &mut Param) {}
 fn has_underscore(_param: bool) {}
 fn enum_matches_param_name(completion_kind: CompletionKind) {}
+fn param_destructuring_omitted_1((a, b): (u32, u32)) {}
+fn param_destructuring_omitted_2(TestVarContainer { test_var: _ }: TestVarContainer) {}
 
 fn twiddle(twiddle: bool) {}
 fn doo(_doo: bool) {}
@@ -746,6 +748,10 @@ fn main() {
     let b: f64 = 4.0;
     let _: f64 = a.div_euclid(b);
     let _: f64 = a.abs_sub(b);
+
+    let range: (u32, u32) = (3, 5);
+    param_destructuring_omitted_1(range);
+    param_destructuring_omitted_2(container);
 }"#,
         );
     }