rust-analyzer

diff --git a/crates/syntax/src/validation.rs b/crates/syntax/src/validation.rs
index 8dc47e0bd3..3ea5844c95 100644
--- a/crates/syntax/src/validation.rs
+++ b/crates/syntax/src/validation.rs

@@ -38,6 +38,7 @@ pub(crate) fn validate(root: &SyntaxNode) -> Vec<SyntaxError> {

ast::PtrType(it) => validate_trait_object_ptr_ty(it, &mut errors),

ast::FnPtrType(it) => validate_trait_object_fn_ptr_ret_ty(it, &mut errors),

ast::MacroRules(it) => validate_macro_rules(it, &mut errors),

+ ast::LetExpr(it) => validate_let_expr(it, &mut errors),

_ => (),

}

@@ -343,3 +344,33 @@ fn validate_const(const_: ast::Const, errors: &mut Vec<SyntaxError>) {

errors.push(SyntaxError::new("const globals cannot be mutable", mut_token.text_range()));

}

+fn validate_let_expr(let_: ast::LetExpr, errors: &mut Vec<SyntaxError>) {

+ let mut token = let_.syntax().clone();

+ loop {

+ token = match token.parent() {

+ Some(it) => it,

+ None => break,

+ };

+ if ast::ParenExpr::can_cast(token.kind()) {

+ continue;

+ } else if let Some(it) = ast::BinExpr::cast(token.clone()) {

+ if it.op_kind() == Some(ast::BinaryOp::LogicOp(ast::LogicOp::And)) {

+ continue;

+ }

+ } else if ast::IfExpr::can_cast(token.kind())

+ || ast::WhileExpr::can_cast(token.kind())

+ || ast::MatchGuard::can_cast(token.kind())

+ {

+ // It must be part of the condition since the expressions are inside a block.

+ return;

+ }

+ break;

+ }

+ errors.push(SyntaxError::new(

+ "`let` expressions are not supported here",

+ let_.syntax().text_range(),

+ ));

diff --git a/crates/syntax/test_data/parser/validation/invalid_let_expr.rast b/crates/syntax/test_data/parser/validation/invalid_let_expr.rast
new file mode 100644
index 0000000000..5b37b59783
--- /dev/null
+++ b/crates/syntax/test_data/parser/validation/invalid_let_expr.rast

@@ -0,0 +1,216 @@