Add support for ExprKind::Let

src/expr.rs

@@ -132,7 +132,7 @@ pub(crate) fn format_expr(
         ast::ExprKind::Tup(ref items) => {
             rewrite_tuple(context, items.iter(), expr.span, shape, items.len() == 1)
         }
-        ast::ExprKind::Let(..) => None,
+        ast::ExprKind::Let(ref pat, ref expr, _span) => rewrite_let(context, shape, pat, expr),
         ast::ExprKind::If(..)
         | ast::ExprKind::ForLoop(..)
         | ast::ExprKind::Loop(..)
@@ -1834,6 +1834,37 @@ fn rewrite_tuple_in_visual_indent_style<'a, T: 'a + IntoOverflowableItem<'a>>(
     Some(format!("({list_str})"))
 }
 
+fn rewrite_let(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    pat: &ast::Pat,
+    expr: &ast::Expr,
+) -> Option<String> {
+    let mut result = "let ".to_owned();
+
+    // 4 = "let ".len()
+    let pat_shape = shape.offset_left(4)?;
+    let pat_str = pat.rewrite(context, pat_shape)?;
+    result.push_str(&pat_str);
+
+    result.push_str(" =");
+
+    let comments_lo = context
+        .snippet_provider
+        .span_after(expr.span.with_lo(pat.span.hi()), "=");
+    let comments_span = mk_sp(comments_lo, expr.span.lo());
+    rewrite_assign_rhs_with_comments(
+        context,
+        result,
+        expr,
+        shape,
+        &RhsAssignKind::Expr(&expr.kind, expr.span),
+        RhsTactics::Default,
+        comments_span,
+        true,
+    )
+}
+
 pub(crate) fn rewrite_tuple<'a, T: 'a + IntoOverflowableItem<'a>>(
     context: &'a RewriteContext<'_>,
     items: impl Iterator<Item = &'a T>,

tests/source/let_chains.rs

@@ -0,0 +1,16 @@
+fn main() {
+    if let x = x && x {}
+
+    if xxx && let x = x {}
+
+    if aaaaaaaaaaaaaaaaaaaaa &&  aaaaaaaaaaaaaaa && aaaaaaaaa && let Some(x) = xxxxxxxxxxxx && aaaaaaa && let None = aaaaaaaaaa {}
+
+    if aaaaaaaaaaaaaaaaaaaaa &&  aaaaaaaaaaaaaaa || aaaaaaaaa && let Some(x) = xxxxxxxxxxxx && aaaaaaa && let None = aaaaaaaaaa {}
+
+    if let Some(Struct { x:TS(1,2) }) = path::to::<_>(hehe)
+        && let [Simple, people] = /* get ready */ create_universe(/* hi */  GreatPowers).initialize_badminton().populate_swamps() &&
+        let    everybody    =    (Loops { hi /*hi*/  , ..loopy() }) || summons::triumphantly() { todo!() }
+
+    if let XXXXXXXXX { xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyy, zzzzzzzzzzzzz} = xxxxxxx()
+    && let Foo = bar() { todo!() }
+}

tests/source/match.rs

@@ -292,6 +292,9 @@ fn guards() {
         aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
             if fooooooooooooooooooooo &&
                (bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb || cccccccccccccccccccccccccccccccccccccccc) => {}
+        Hi { friend } if let None = friend => {}
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa if let Some(foooooooooooooo) = hiiiiiiiiiiiiiii => {}
+        aaaaaaaaaaaaaaaaa if let Superman { powers: Some(goteem), .. } = all::get_random_being::<Super>() => {}
     }
 }
 

tests/target/let_chains.rs

@@ -0,0 +1,41 @@
+fn main() {
+    if let x = x && x {}
+
+    if xxx && let x = x {}
+
+    if aaaaaaaaaaaaaaaaaaaaa
+        && aaaaaaaaaaaaaaa
+        && aaaaaaaaa
+        && let Some(x) = xxxxxxxxxxxx
+        && aaaaaaa
+        && let None = aaaaaaaaaa
+    {}
+
+    if aaaaaaaaaaaaaaaaaaaaa && aaaaaaaaaaaaaaa
+        || aaaaaaaaa && let Some(x) = xxxxxxxxxxxx && aaaaaaa && let None = aaaaaaaaaa
+    {}
+
+    if let Some(Struct { x: TS(1, 2) }) = path::to::<_>(hehe)
+        && let [Simple, people] = /* get ready */
+            create_universe(/* hi */ GreatPowers)
+                .initialize_badminton()
+                .populate_swamps()
+        && let everybody = (Loops {
+            hi, /*hi*/
+            ..loopy()
+        })
+        || summons::triumphantly()
+    {
+        todo!()
+    }
+
+    if let XXXXXXXXX {
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        yyyyyyyyyyyyy,
+        zzzzzzzzzzzzz,
+    } = xxxxxxx()
+        && let Foo = bar()
+    {
+        todo!()
+    }
+}

tests/target/match.rs

@@ -317,6 +317,14 @@ fn guards() {
             if fooooooooooooooooooooo
                 && (bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
                     || cccccccccccccccccccccccccccccccccccccccc) => {}
+        Hi { friend } if let None = friend => {}
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+            if let Some(foooooooooooooo) = hiiiiiiiiiiiiiii => {}
+        aaaaaaaaaaaaaaaaa
+            if let Superman {
+                powers: Some(goteem),
+                ..
+            } = all::get_random_being::<Super>() => {}
     }
 }