Auto merge of #17377 - Young-Flash:hir_print, r=Veykril

internal: better print style for hir

before:
![before](https://github.com/rust-lang/rust-analyzer/assets/71162630/cd5e27b3-b4b1-450f-ba50-3c4f4e345d70)

after:
![after](https://github.com/rust-lang/rust-analyzer/assets/71162630/04e11345-cadd-49cb-b10c-6888ef51758e)

2 files changed, 17 insertions, 8 deletions

diff --git a/src/tools/rust-analyzer/crates/hir-def/src/body/pretty.rs b/src/tools/rust-analyzer/crates/hir-def/src/body/pretty.rs
index cbb5ca887f4..c48d16d0530 100644
--- a/src/tools/rust-analyzer/crates/hir-def/src/body/pretty.rs
+++ b/src/tools/rust-analyzer/crates/hir-def/src/body/pretty.rs
@@ -48,21 +48,30 @@ pub(super) fn print_body_hir(db: &dyn DefDatabase, body: &Body, owner: DefWithBo
     let mut p = Printer { db, body, buf: header, indent_level: 0, needs_indent: false };
     if let DefWithBodyId::FunctionId(it) = owner {
         p.buf.push('(');
-        let params = &db.function_data(it).params;
-        let mut params = params.iter();
+        let function_data = &db.function_data(it);
+        let (mut params, ret_type) = (function_data.params.iter(), &function_data.ret_type);
         if let Some(self_param) = body.self_param {
             p.print_binding(self_param);
-            p.buf.push(':');
+            p.buf.push_str(": ");
             if let Some(ty) = params.next() {
                 p.print_type_ref(ty);
+                p.buf.push_str(", ");
             }
         }
         body.params.iter().zip(params).for_each(|(&param, ty)| {
             p.print_pat(param);
-            p.buf.push(':');
+            p.buf.push_str(": ");
             p.print_type_ref(ty);
+            p.buf.push_str(", ");
         });
+        // remove the last ", " in param list
+        if body.params.len() > 0 {
+            p.buf.truncate(p.buf.len() - 2);
+        }
         p.buf.push(')');
+        // return type
+        p.buf.push_str(" -> ");
+        p.print_type_ref(ret_type);
         p.buf.push(' ');
     }
     p.print_expr(body.body_expr);
diff --git a/src/tools/rust-analyzer/crates/hir-def/src/body/tests.rs b/src/tools/rust-analyzer/crates/hir-def/src/body/tests.rs
index e8b26d53734..0011d3a20c2 100644
--- a/src/tools/rust-analyzer/crates/hir-def/src/body/tests.rs
+++ b/src/tools/rust-analyzer/crates/hir-def/src/body/tests.rs
@@ -156,7 +156,7 @@ fn main() {
     );
 
     expect![[r#"
-        fn main() {
+        fn main() -> () {
             let are = "are";
             let count = 10;
             builtin#lang(Arguments::new_v1_formatted)(
@@ -258,7 +258,7 @@ impl SsrError {
 
     assert_eq!(db.body_with_source_map(def).1.diagnostics(), &[]);
     expect![[r#"
-        fn main() {
+        fn main() -> () {
             _ = $crate::error::SsrError::new(
                 builtin#lang(Arguments::new_v1_formatted)(
                     &[
@@ -303,7 +303,7 @@ macro_rules! m {
     };
 }
 
-fn f() {
+fn f(a: i32, b: u32) -> String {
     m!();
 }
 "#,
@@ -317,7 +317,7 @@ fn f() {
     }
 
     expect![[r#"
-        fn f() {
+        fn f(a: i32, b: u32) -> String {
             {
                 $crate::panicking::panic_fmt(
                     builtin#lang(Arguments::new_v1_formatted)(