Merge #10440

10440: Fix Clippy warnings and replace some `if let`s with `match` r=Veykril a=arzg

I decided to try fixing a bunch of Clippy warnings. I am aware of this project’s opinion of Clippy (I have read both [rust-lang/clippy#5537](https://github.com/rust-lang/rust-clippy/issues/5537) and [rust-analyzer/rowan#57 (comment)](https://github.com/rust-analyzer/rowan/pull/57#discussion_r415676159)), so I totally understand if part of or the entirety of this PR is rejected. In particular, I can see how the semicolons and `if let` vs `match` commits provide comparatively little benefit when compared to the ensuing churn.

I tried to separate each kind of change into its own commit to make it easier to discard certain changes. I also only applied Clippy suggestions where I thought they provided a definite improvement to the code (apart from semicolons, which is IMO more of a formatting/consistency question than a linting question). In the end I accumulated a list of 28 Clippy lints I ignored entirely.

Sidenote: I should really have asked about this on Zulip before going through all 1,555 `if let`s in the codebase to decide which ones definitely look better as `match` :P

Co-authored-by: Aramis Razzaghipour <aramisnoah@gmail.com>

crates/ide/src/display/navigation_target.rs

@@ -292,10 +292,9 @@ impl TryToNav for hir::Impl {
     fn try_to_nav(&self, db: &RootDatabase) -> Option<NavigationTarget> {
         let src = self.source(db)?;
         let derive_attr = self.is_builtin_derive(db);
-        let frange = if let Some(item) = &derive_attr {
-            item.syntax().original_file_range(db)
-        } else {
-            src.syntax().original_file_range(db)
+        let frange = match &derive_attr {
+            Some(item) => item.syntax().original_file_range(db),
+            None => src.syntax().original_file_range(db),
         };
         let focus_range = if derive_attr.is_some() {
             None

crates/ide/src/join_lines.rs

@@ -136,10 +136,9 @@ fn remove_newline(
             }
             T!['}'] => {
                 // Removes: comma, newline (incl. surrounding whitespace)
-                let space = if let Some(left) = prev.prev_sibling_or_token() {
-                    compute_ws(left.kind(), next.kind())
-                } else {
-                    " "
+                let space = match prev.prev_sibling_or_token() {
+                    Some(left) => compute_ws(left.kind(), next.kind()),
+                    None => " ",
                 };
                 edit.replace(
                     TextRange::new(prev.text_range().start(), token.text_range().end()),

crates/ide/src/rename.rs

@@ -156,7 +156,7 @@ fn rename_to_self(sema: &Semantics<RootDatabase>, local: hir::Local) -> RenameRe
         _ => bail!("Cannot rename local to self outside of function"),
     };
 
-    if let Some(_) = fn_def.self_param(sema.db) {
+    if fn_def.self_param(sema.db).is_some() {
         bail!("Method already has a self parameter");
     }
 

crates/ide/src/static_index.rs

@@ -103,10 +103,9 @@ impl StaticIndex<'_> {
         for token in tokens {
             let range = token.text_range();
             let node = token.parent().unwrap();
-            let def = if let Some(x) = get_definition(&sema, token.clone()) {
-                x
-            } else {
-                continue;
+            let def = match get_definition(&sema, token.clone()) {
+                Some(x) => x,
+                None => continue,
             };
             let id = if let Some(x) = self.def_map.get(&def) {
                 *x
@@ -124,10 +123,9 @@ impl StaticIndex<'_> {
             let token = self.tokens.get_mut(id).unwrap();
             token.references.push(ReferenceData {
                 range: FileRange { range, file_id },
-                is_definition: if let Some(x) = def.try_to_nav(self.db) {
-                    x.file_id == file_id && x.focus_or_full_range() == range
-                } else {
-                    false
+                is_definition: match def.try_to_nav(self.db) {
+                    Some(x) => x.file_id == file_id && x.focus_or_full_range() == range,
+                    None => false,
                 },
             });
             result.tokens.push((range, id));

crates/ide/src/syntax_highlighting.rs

@@ -330,7 +330,7 @@ fn traverse(
             }
         }
 
-        if let Some(_) = macro_highlighter.highlight(element_to_highlight.clone()) {
+        if macro_highlighter.highlight(element_to_highlight.clone()).is_some() {
             continue;
         }