rustfmt: Also allow bool literals as first item of let chain

src/tools/rustfmt/src/pairs.rs

@@ -1,4 +1,4 @@
-use rustc_ast::ast;
+use rustc_ast::{ast, token};
 use rustc_span::Span;
 
 use crate::config::IndentStyle;
@@ -272,13 +272,17 @@ struct PairList<'a, 'b, T: Rewrite> {
     span: Span,
 }
 
-fn is_ident(expr: &ast::Expr) -> bool {
+fn is_ident_or_bool_lit(expr: &ast::Expr) -> bool {
     match &expr.kind {
         ast::ExprKind::Path(None, path) if path.segments.len() == 1 => true,
+        ast::ExprKind::Lit(token::Lit {
+            kind: token::LitKind::Bool,
+            ..
+        }) => true,
         ast::ExprKind::Unary(_, expr)
         | ast::ExprKind::AddrOf(_, _, expr)
         | ast::ExprKind::Paren(expr)
-        | ast::ExprKind::Try(expr) => is_ident(expr),
+        | ast::ExprKind::Try(expr) => is_ident_or_bool_lit(expr),
         _ => false,
     }
 }
@@ -296,10 +300,10 @@ impl<'a, 'b> PairList<'a, 'b, ast::Expr> {
             return false;
         }
 
-        let fist_item_is_ident = is_ident(self.list[0].0);
+        let fist_item_is_ident_or_bool_lit = is_ident_or_bool_lit(self.list[0].0);
         let second_item_is_let_chain = matches!(self.list[1].0.kind, ast::ExprKind::Let(..));
 
-        fist_item_is_ident && second_item_is_let_chain
+        fist_item_is_ident_or_bool_lit && second_item_is_let_chain
     }
 }
 

src/tools/rustfmt/tests/source/let_chains.rs

@@ -20,6 +20,11 @@ fn test_single_line_let_chain() {
     if a && let Some(b) = foo() {
     }
 
+    // first item in let-chain is a bool literal
+    if true && let Some(x) = y {
+
+    }
+
     // first item in let-chain is a unary ! with an ident
     let unary_not = if !from_hir_call
         && let Some(p) = parent
@@ -94,11 +99,6 @@ fn test_multi_line_let_chain() {
 
     }
 
-    // bool literal
-    if true && let Some(x) = y {
-
-    }
-
     // cast to a bool
     if 1 as bool && let Some(x) = y {
 

src/tools/rustfmt/tests/target/let_chains.rs

@@ -50,6 +50,9 @@ fn test_single_line_let_chain() {
     // first item in let-chain is an ident
     if a && let Some(b) = foo() {}
 
+    // first item in let-chain is a bool literal
+    if true && let Some(x) = y {}
+
     // first item in let-chain is a unary ! with an ident
     let unary_not = if !from_hir_call && let Some(p) = parent {};
 
@@ -102,11 +105,6 @@ fn test_multi_line_let_chain() {
         && let Some(x) = y
     {}
 
-    // bool literal
-    if true
-        && let Some(x) = y
-    {}
-
     // cast to a bool
     if 1 as bool
         && let Some(x) = y