Rollup merge of #137423 - Urgau:imprv-pretty-hir, r=compiler-errors

Improve a bit HIR pretty printer

This PR improve (a bit) the HIR pretty printer.

It does so by:
 - Not printing elided lifetimes (those are not expressible in surface Rust anyway)
 - And by rendering implicit self with the shorthand syntax

I also tried fixing some indentation and other things but gave up for now.

Best reviewed commit by commit.

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -424,20 +424,23 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         self.ann_post(ident)
     }
 
-    fn strsep<T, F>(
+    fn strsep<'x, T: 'x, F, I>(
         &mut self,
         sep: &'static str,
         space_before: bool,
         b: Breaks,
-        elts: &[T],
+        elts: I,
         mut op: F,
     ) where
         F: FnMut(&mut Self, &T),
+        I: IntoIterator<Item = &'x T>,
     {
+        let mut it = elts.into_iter();
+
         self.rbox(0, b);
-        if let Some((first, rest)) = elts.split_first() {
+        if let Some(first) = it.next() {
             op(self, first);
-            for elt in rest {
+            for elt in it {
                 if space_before {
                     self.space();
                 }
@@ -448,9 +451,10 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         self.end();
     }
 
-    fn commasep<T, F>(&mut self, b: Breaks, elts: &[T], op: F)
+    fn commasep<'x, T: 'x, F, I>(&mut self, b: Breaks, elts: I, op: F)
     where
         F: FnMut(&mut Self, &T),
+        I: IntoIterator<Item = &'x T>,
     {
         self.strsep(",", false, b, elts, op)
     }

compiler/rustc_hir_pretty/src/lib.rs

@@ -18,7 +18,8 @@ use rustc_ast_pretty::pprust::state::MacHeader;
 use rustc_ast_pretty::pprust::{Comments, PrintState};
 use rustc_hir::{
     BindingMode, ByRef, ConstArgKind, GenericArg, GenericBound, GenericParam, GenericParamKind,
-    HirId, LifetimeParamKind, Node, PatKind, PreciseCapturingArg, RangeEnd, Term, TyPatKind,
+    HirId, ImplicitSelfKind, LifetimeParamKind, Node, PatKind, PreciseCapturingArg, RangeEnd, Term,
+    TyPatKind,
 };
 use rustc_span::source_map::SourceMap;
 use rustc_span::{FileName, Ident, Span, Symbol, kw};
@@ -2086,6 +2087,28 @@ impl<'a> State<'a> {
         self.print_pat(arg.pat);
     }
 
+    fn print_implicit_self(&mut self, implicit_self_kind: &hir::ImplicitSelfKind) {
+        match implicit_self_kind {
+            ImplicitSelfKind::Imm => {
+                self.word("self");
+            }
+            ImplicitSelfKind::Mut => {
+                self.print_mutability(hir::Mutability::Mut, false);
+                self.word("self");
+            }
+            ImplicitSelfKind::RefImm => {
+                self.word("&");
+                self.word("self");
+            }
+            ImplicitSelfKind::RefMut => {
+                self.word("&");
+                self.print_mutability(hir::Mutability::Mut, false);
+                self.word("self");
+            }
+            ImplicitSelfKind::None => unreachable!(),
+        }
+    }
+
     fn print_arm(&mut self, arm: &hir::Arm<'_>) {
         // I have no idea why this check is necessary, but here it
         // is :(
@@ -2151,27 +2174,33 @@ impl<'a> State<'a> {
         // Make sure we aren't supplied *both* `arg_names` and `body_id`.
         assert!(arg_names.is_empty() || body_id.is_none());
         let mut i = 0;
-        let mut print_arg = |s: &mut Self| {
-            if let Some(arg_name) = arg_names.get(i) {
-                s.word(arg_name.to_string());
-                s.word(":");
-                s.space();
-            } else if let Some(body_id) = body_id {
-                s.ann.nested(s, Nested::BodyParamPat(body_id, i));
-                s.word(":");
-                s.space();
+        let mut print_arg = |s: &mut Self, ty: Option<&hir::Ty<'_>>| {
+            if i == 0 && decl.implicit_self.has_implicit_self() {
+                s.print_implicit_self(&decl.implicit_self);
+            } else {
+                if let Some(arg_name) = arg_names.get(i) {
+                    s.word(arg_name.to_string());
+                    s.word(":");
+                    s.space();
+                } else if let Some(body_id) = body_id {
+                    s.ann.nested(s, Nested::BodyParamPat(body_id, i));
+                    s.word(":");
+                    s.space();
+                }
+                if let Some(ty) = ty {
+                    s.print_type(ty);
+                }
             }
             i += 1;
         };
         self.commasep(Inconsistent, decl.inputs, |s, ty| {
             s.ibox(INDENT_UNIT);
-            print_arg(s);
-            s.print_type(ty);
+            print_arg(s, Some(ty));
             s.end();
         });
         if decl.c_variadic {
             self.word(", ");
-            print_arg(self);
+            print_arg(self, None);
             self.word("...");
         }
         self.pclose();
@@ -2284,7 +2313,9 @@ impl<'a> State<'a> {
                 GenericBound::Use(args, _) => {
                     self.word("use <");
 
-                    self.commasep(Inconsistent, args, |s, arg| s.print_precise_capturing_arg(*arg));
+                    self.commasep(Inconsistent, *args, |s, arg| {
+                        s.print_precise_capturing_arg(*arg)
+                    });
 
                     self.word(">");
                 }
@@ -2300,10 +2331,23 @@ impl<'a> State<'a> {
     }
 
     fn print_generic_params(&mut self, generic_params: &[GenericParam<'_>]) {
-        if !generic_params.is_empty() {
+        let is_lifetime_elided = |generic_param: &GenericParam<'_>| {
+            matches!(
+                generic_param.kind,
+                GenericParamKind::Lifetime { kind: LifetimeParamKind::Elided(_) }
+            )
+        };
+
+        // We don't want to show elided lifetimes as they are compiler-inserted and not
+        // expressible in surface level Rust.
+        if !generic_params.is_empty() && !generic_params.iter().all(is_lifetime_elided) {
             self.word("<");
 
-            self.commasep(Inconsistent, generic_params, |s, param| s.print_generic_param(param));
+            self.commasep(
+                Inconsistent,
+                generic_params.iter().filter(|gp| !is_lifetime_elided(gp)),
+                |s, param| s.print_generic_param(param),
+            );
 
             self.word(">");
         }

tests/ui/unpretty/debug-fmt-hir.rs

@@ -0,0 +1,26 @@
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+use std::fmt;
+
+pub struct Bar {
+    a: String,
+    b: u8,
+}
+
+impl fmt::Debug for Bar {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        debug_struct_field2_finish(f, "Bar", "a", &self.a, "b", &&self.b)
+    }
+}
+
+fn debug_struct_field2_finish<'a>(
+    name: &str,
+    name1: &str,
+    value1: &'a dyn fmt::Debug,
+    name2: &str,
+    value2: &'a dyn fmt::Debug,
+) -> fmt::Result
+{
+    loop {}
+}

tests/ui/unpretty/debug-fmt-hir.stdout

@@ -0,0 +1,25 @@
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+use std::fmt;
+
+struct Bar {
+    a: String,
+    b: u8,
+}
+
+impl fmt::Debug for Bar {
+    fn fmt(&self, f: &'_ mut fmt::Formatter<'_>)
+        ->
+            fmt::Result {
+        debug_struct_field2_finish(f, "Bar", "a", &self.a, "b", &&self.b)
+    }
+}
+
+fn debug_struct_field2_finish<'a>(name: &'_ str, name1: &'_ str,
+    value1: &'a dyn fmt::Debug, name2: &'_ str, value2: &'a dyn fmt::Debug)
+    -> fmt::Result { loop { } }

tests/ui/unpretty/self-hir.rs

@@ -0,0 +1,14 @@
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+pub struct Bar {
+    a: String,
+    b: u8,
+}
+
+impl Bar {
+    fn imm_self(self) {}
+    fn mut_self(mut self) {}
+    fn refimm_self(&self) {}
+    fn refmut_self(&mut self) {}
+}

tests/ui/unpretty/self-hir.stdout

@@ -0,0 +1,18 @@
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+struct Bar {
+    a: String,
+    b: u8,
+}
+
+impl Bar {
+    fn imm_self(self) { }
+    fn mut_self(mut self) { }
+    fn refimm_self(&self) { }
+    fn refmut_self(&mut self) { }
+}