Auto merge of #17941 - ChayimFriedman2:pre-closure-to-fn, r=Veykril

Preliminary work for #17940

I split the PR as requested, and made small commits.

crates/syntax/src/ast/edit.rs

@@ -8,7 +8,7 @@ use crate::{
     ted, AstToken, NodeOrToken, SyntaxElement, SyntaxNode, SyntaxToken,
 };
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct IndentLevel(pub u8);
 
 impl From<u8> for IndentLevel {

crates/syntax/src/ast/generated/nodes.rs

@@ -486,6 +486,8 @@ impl Fn {
     #[inline]
     pub fn fn_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![fn]) }
     #[inline]
+    pub fn gen_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![gen]) }
+    #[inline]
     pub fn unsafe_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![unsafe]) }
 }
 

crates/syntax/src/ast/make.rs

@@ -1035,6 +1035,7 @@ pub fn fn_(
     is_async: bool,
     is_const: bool,
     is_unsafe: bool,
+    is_gen: bool,
 ) -> ast::Fn {
     let type_params = match type_params {
         Some(type_params) => format!("{type_params}"),
@@ -1056,9 +1057,10 @@ pub fn fn_(
     let async_literal = if is_async { "async " } else { "" };
     let const_literal = if is_const { "const " } else { "" };
     let unsafe_literal = if is_unsafe { "unsafe " } else { "" };
+    let gen_literal = if is_gen { "gen " } else { "" };
 
     ast_from_text(&format!(
-        "{visibility}{async_literal}{const_literal}{unsafe_literal}fn {fn_name}{type_params}{params} {ret_type}{where_clause}{body}",
+        "{visibility}{const_literal}{async_literal}{gen_literal}{unsafe_literal}fn {fn_name}{type_params}{params} {ret_type}{where_clause}{body}",
     ))
 }
 pub fn struct_(

crates/syntax/src/ast/node_ext.rs

@@ -17,7 +17,7 @@ use crate::{
     ted, NodeOrToken, SmolStr, SyntaxElement, SyntaxToken, TokenText, T,
 };
 
-use super::{RangeItem, RangeOp};
+use super::{GenericParam, RangeItem, RangeOp};
 
 impl ast::Lifetime {
     pub fn text(&self) -> TokenText<'_> {
@@ -822,6 +822,15 @@ pub enum TypeOrConstParam {
     Const(ast::ConstParam),
 }
 
+impl From<TypeOrConstParam> for GenericParam {
+    fn from(value: TypeOrConstParam) -> Self {
+        match value {
+            TypeOrConstParam::Type(it) => GenericParam::TypeParam(it),
+            TypeOrConstParam::Const(it) => GenericParam::ConstParam(it),
+        }
+    }
+}
+
 impl TypeOrConstParam {
     pub fn name(&self) -> Option<ast::Name> {
         match self {

crates/syntax/src/hacks.rs

@@ -6,9 +6,9 @@ use parser::Edition;
 
 use crate::{ast, AstNode};
 
-pub fn parse_expr_from_str(s: &str) -> Option<ast::Expr> {
+pub fn parse_expr_from_str(s: &str, edition: Edition) -> Option<ast::Expr> {
     let s = s.trim();
-    let file = ast::SourceFile::parse(&format!("const _: () = {s};"), Edition::CURRENT);
+    let file = ast::SourceFile::parse(&format!("const _: () = {s};"), edition);
     let expr = file.syntax_node().descendants().find_map(ast::Expr::cast)?;
     if expr.syntax().text() != s {
         return None;