Rollup merge of #150695 - Kivooeo:pretty-printing, r=BoxyUwU

MGCA: pretty printing for struct expressions and tuple calls

not sure

1. if there any tests that i need to adjust
2. if i should add any test for it
3. if humanity has come up with anything better than checking if that's first iteration or not with flag when printing sequences with separator

in case there is no tests for it and i dont have to add any, there is a demonstration of this ✨ pretty ✨ printing (this is output from `-Z unpretty=hir`)

```
fn test_errors<const N:
    usize>() {
    // accepts_enum::<{ None::<u32> }>();
    accepts_point::<Point1 { a: N, b: N }>();
    accepts_point::<Point(N, N)>();
}
```

btw it does not print const block

for this

```
accepts_point::<{ Point1 { a: const {N + 1}, b: N } }>();
```

it will print

```
accepts_point::<Point1 { a: { N + 1 }, b: N }>();
```

not sure if we want to print const blocks or not

r? BoxyUwU

compiler/rustc_hir_pretty/src/lib.rs

@@ -17,9 +17,9 @@ use rustc_ast_pretty::pprust::state::MacHeader;
 use rustc_ast_pretty::pprust::{Comments, PrintState};
 use rustc_hir::attrs::{AttributeKind, PrintAttribute};
 use rustc_hir::{
-    BindingMode, ByRef, ConstArgKind, GenericArg, GenericBound, GenericParam, GenericParamKind,
-    HirId, ImplicitSelfKind, LifetimeParamKind, Node, PatKind, PreciseCapturingArg, RangeEnd, Term,
-    TyPatKind,
+    BindingMode, ByRef, ConstArg, ConstArgExprField, ConstArgKind, GenericArg, GenericBound,
+    GenericParam, GenericParamKind, HirId, ImplicitSelfKind, LifetimeParamKind, Node, PatKind,
+    PreciseCapturingArg, RangeEnd, Term, TyPatKind,
 };
 use rustc_span::source_map::SourceMap;
 use rustc_span::{DUMMY_SP, FileName, Ident, Span, Symbol, kw, sym};
@@ -1141,9 +1141,8 @@ impl<'a> State<'a> {
 
     fn print_const_arg(&mut self, const_arg: &hir::ConstArg<'_>) {
         match &const_arg.kind {
-            // FIXME(mgca): proper printing for struct exprs
-            ConstArgKind::Struct(..) => self.word("/* STRUCT EXPR */"),
-            ConstArgKind::TupleCall(..) => self.word("/* TUPLE CALL */"),
+            ConstArgKind::Struct(qpath, fields) => self.print_const_struct(qpath, fields),
+            ConstArgKind::TupleCall(qpath, args) => self.print_const_ctor(qpath, args),
             ConstArgKind::Path(qpath) => self.print_qpath(qpath, true),
             ConstArgKind::Anon(anon) => self.print_anon_const(anon),
             ConstArgKind::Error(_, _) => self.word("/*ERROR*/"),
@@ -1151,6 +1150,31 @@ impl<'a> State<'a> {
         }
     }
 
+    fn print_const_struct(&mut self, qpath: &hir::QPath<'_>, fields: &&[&ConstArgExprField<'_>]) {
+        self.print_qpath(qpath, true);
+        self.word(" ");
+        self.word("{");
+        if !fields.is_empty() {
+            self.nbsp();
+        }
+        self.commasep(Inconsistent, *fields, |s, field| {
+            s.word(field.field.as_str().to_string());
+            s.word(":");
+            s.nbsp();
+            s.print_const_arg(field.expr);
+        });
+        self.word("}");
+    }
+
+    fn print_const_ctor(&mut self, qpath: &hir::QPath<'_>, args: &&[&ConstArg<'_, ()>]) {
+        self.print_qpath(qpath, true);
+        self.word("(");
+        self.commasep(Inconsistent, *args, |s, arg| {
+            s.print_const_arg(arg);
+        });
+        self.word(")");
+    }
+
     fn print_call_post(&mut self, args: &[hir::Expr<'_>]) {
         self.popen();
         self.commasep_exprs(Inconsistent, args);

tests/ui/unpretty/struct-exprs-tuple-call-pretty-printing.rs

@@ -0,0 +1,33 @@
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+#![feature(min_generic_const_args, adt_const_params)]
+#![expect(incomplete_features)]
+#![allow(dead_code)]
+
+use std::marker::ConstParamTy;
+
+struct Point(u32, u32);
+
+struct Point3();
+
+struct Point1 {
+    a: u32,
+    b: u32,
+}
+
+struct Point2 {}
+
+fn with_point<const P: Point>() {}
+fn with_point1<const P: Point1>() {}
+fn with_point2<const P: Point2>() {}
+fn with_point3<const P: Point3>() {}
+
+fn test<const N: u32>() {
+    with_point::<{ Point(N, N) }>();
+    with_point1::<{ Point1 { a: N, b: N } }>();
+    with_point2::<{ Point2 {} }>();
+    with_point3::<{ Point3() }>();
+}
+
+fn main() {}

tests/ui/unpretty/struct-exprs-tuple-call-pretty-printing.stdout

@@ -0,0 +1,39 @@
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+#![feature(min_generic_const_args, adt_const_params)]
+#![expect(incomplete_features)]
+#![allow(dead_code)]
+#[attr = MacroUse {arguments: UseAll}]
+extern crate std;
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+
+use std::marker::ConstParamTy;
+
+struct Point(u32, u32);
+
+struct Point3();
+
+struct Point1 {
+    a: u32,
+    b: u32,
+}
+
+struct Point2 {
+}
+
+fn with_point<const P: Point>() { }
+fn with_point1<const P: Point1>() { }
+fn with_point2<const P: Point2>() { }
+fn with_point3<const P: Point3>() { }
+
+fn test<const N:
+    u32>() {
+    with_point::<Point(N, N)>();
+    with_point1::<Point1 { a: N, b: N}>();
+    with_point2::<Point2 {}>();
+    with_point3::<Point3()>();
+}
+
+fn main() { }