Auto merge of #14361 - Veykril:if-then-parse, r=Veykril

fix: Fix `ast::IfExpr` child accessors

Fixes https://github.com/rust-lang/rust-analyzer/issues/14360

crates/hir-expand/src/fixup.rs

@@ -636,9 +636,8 @@ fn foo() {
     if {}
 }
 "#,
-            // the {} gets parsed as the condition, I think?
             expect![[r#"
-fn foo () {if {} {}}
+fn foo () {if __ra_fixup {} {}}
 "#]],
         )
     }

crates/syntax/src/ast/expr_ext.rs

@@ -48,23 +48,30 @@ fn from(if_expr: ast::IfExpr) -> Self {
 }
 
 impl ast::IfExpr {
+    pub fn condition(&self) -> Option<ast::Expr> {
+        // If the condition is a BlockExpr, check if the then body is missing.
+        // If it is assume the condition is the expression that is missing instead.
+        let mut exprs = support::children(self.syntax());
+        let first = exprs.next();
+        match first {
+            Some(ast::Expr::BlockExpr(_)) => exprs.next().and(first),
+            first => first,
+        }
+    }
+
     pub fn then_branch(&self) -> Option<ast::BlockExpr> {
-        self.children_after_condition().next()
+        match support::children(self.syntax()).nth(1)? {
+            ast::Expr::BlockExpr(block) => Some(block),
+            _ => None,
+        }
     }
 
     pub fn else_branch(&self) -> Option<ElseBranch> {
-        let res = match self.children_after_condition().nth(1) {
-            Some(block) => ElseBranch::Block(block),
-            None => {
-                let elif = self.children_after_condition().next()?;
-                ElseBranch::IfExpr(elif)
-            }
-        };
-        Some(res)
-    }
-
-    fn children_after_condition<N: AstNode>(&self) -> impl Iterator<Item = N> {
-        self.syntax().children().skip(1).filter_map(N::cast)
+        match support::children(self.syntax()).nth(2)? {
+            ast::Expr::BlockExpr(block) => Some(ElseBranch::Block(block)),
+            ast::Expr::IfExpr(elif) => Some(ElseBranch::IfExpr(elif)),
+            _ => None,
+        }
     }
 }
 

crates/syntax/src/ast/node_ext.rs

@@ -937,12 +937,6 @@ fn from(it: ast::Adt) -> Self {
     }
 }
 
-impl ast::IfExpr {
-    pub fn condition(&self) -> Option<ast::Expr> {
-        support::child(&self.syntax)
-    }
-}
-
 impl ast::MatchGuard {
     pub fn condition(&self) -> Option<ast::Expr> {
         support::child(&self.syntax)