Merge #10491

10491: Support nested type on replace if let with match r=k-nasa a=k-nasa

## Why

close: https://github.com/rust-analyzer/rust-analyzer/issues/8690

Now, Replacing if-let with match cant't output exhaustive patterns code.
This was because the `else` conversion used specific types (ex. Option, Result) instead of wildcards.

I thought it was more of a problem to generate non-exhaustive patterns than the benefits of using the concrete one.

How about using wildcards in `else`? 
Is this change policy acceptable?

## What

- using wildcards on `make_else_arm`
- Change test cases

Co-authored-by: k-nasa <htilcs1115@gmail.com>

crates/ide_assists/src/utils.rs

@@ -285,6 +285,47 @@ pub(crate) fn does_pat_match_variant(pat: &ast::Pat, var: &ast::Pat) -> bool {
     pat_head == var_head
 }
 
+pub(crate) fn does_nested_pattern(pat: &ast::Pat) -> bool {
+    let depth = calc_depth(pat, 0);
+
+    if 1 < depth {
+        return true;
+    }
+    false
+}
+
+fn calc_depth(pat: &ast::Pat, depth: usize) -> usize {
+    match pat {
+        ast::Pat::IdentPat(_)
+        | ast::Pat::BoxPat(_)
+        | ast::Pat::RestPat(_)
+        | ast::Pat::LiteralPat(_)
+        | ast::Pat::MacroPat(_)
+        | ast::Pat::OrPat(_)
+        | ast::Pat::ParenPat(_)
+        | ast::Pat::PathPat(_)
+        | ast::Pat::WildcardPat(_)
+        | ast::Pat::RangePat(_)
+        | ast::Pat::RecordPat(_)
+        | ast::Pat::RefPat(_)
+        | ast::Pat::SlicePat(_)
+        | ast::Pat::TuplePat(_)
+        | ast::Pat::ConstBlockPat(_) => depth,
+
+        // FIXME: Other patterns may also be nested. Currently it simply supports only `TupleStructPat`
+        ast::Pat::TupleStructPat(pat) => {
+            let mut max_depth = depth;
+            for p in pat.fields() {
+                let d = calc_depth(&p, depth + 1);
+                if d > max_depth {
+                    max_depth = d
+                }
+            }
+            max_depth
+        }
+    }
+}
+
 // Uses a syntax-driven approach to find any impl blocks for the struct that
 // exist within the module/file
 //