ty: remove obsolete printer

This commit removes the obsolete printer and replaces all uses of it
with `FmtPrinter`. Of the replaced uses, all but one use was in `debug!`
logging, two cases were notable:

- `MonoItem::to_string` is used in `-Z print-mono-items` and therefore
  affects the output of all codegen-units tests.
- `DefPathBasedNames` was used in `librustc_codegen_llvm/type_of.rs`
  with `LLVMStructCreateNamed` and that'll now get different values, but
  this should result in no functional change.

Signed-off-by: David Wood <david@davidtw.co>

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -4,7 +4,6 @@ use crate::type_::Type;
 use rustc_codegen_ssa::traits::*;
 use rustc_middle::bug;
 use rustc_middle::ty::layout::{FnAbiExt, TyAndLayout};
-use rustc_middle::ty::print::obsolete::DefPathBasedNames;
 use rustc_middle::ty::{self, Ty, TypeFoldable};
 use rustc_target::abi::{Abi, AddressSpace, Align, FieldsShape};
 use rustc_target::abi::{Int, Pointer, F32, F64};
@@ -60,9 +59,7 @@ fn uncached_llvm_type<'a, 'tcx>(
         // ty::Dynamic(..) |
         ty::Foreign(..) |
         ty::Str => {
-            let mut name = String::with_capacity(32);
-            let printer = DefPathBasedNames::new(cx.tcx, true, true);
-            printer.push_type_name(layout.ty, &mut name, false);
+            let mut name = layout.ty.to_string();
             if let (&ty::Adt(def, _), &Variants::Single { index })
                  = (&layout.ty.kind, &layout.variants)
             {

compiler/rustc_codegen_ssa/src/mono_item.rs

@@ -21,7 +21,7 @@ impl<'a, 'tcx: 'a> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
     fn define<Bx: BuilderMethods<'a, 'tcx>>(&self, cx: &'a Bx::CodegenCx) {
         debug!(
             "BEGIN IMPLEMENTING '{} ({})' in cgu {}",
-            self.to_string(cx.tcx(), true),
+            self,
             self.to_raw_string(),
             cx.codegen_unit().name()
         );
@@ -45,7 +45,7 @@ impl<'a, 'tcx: 'a> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
 
         debug!(
             "END IMPLEMENTING '{} ({})' in cgu {}",
-            self.to_string(cx.tcx(), true),
+            self,
             self.to_raw_string(),
             cx.codegen_unit().name()
         );
@@ -59,7 +59,7 @@ impl<'a, 'tcx: 'a> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
     ) {
         debug!(
             "BEGIN PREDEFINING '{} ({})' in cgu {}",
-            self.to_string(cx.tcx(), true),
+            self,
             self.to_raw_string(),
             cx.codegen_unit().name()
         );
@@ -80,7 +80,7 @@ impl<'a, 'tcx: 'a> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
 
         debug!(
             "END PREDEFINING '{} ({})' in cgu {}",
-            self.to_string(cx.tcx(), true),
+            self,
             self.to_raw_string(),
             cx.codegen_unit().name()
         );

compiler/rustc_middle/src/mir/mono.rs

@@ -1,6 +1,5 @@
 use crate::dep_graph::{DepConstructor, DepNode, WorkProduct, WorkProductId};
 use crate::ich::{NodeIdHashingMode, StableHashingContext};
-use crate::ty::print::obsolete::DefPathBasedNames;
 use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt};
 use rustc_attr::InlineAttr;
 use rustc_data_structures::base_n;
@@ -171,30 +170,6 @@ impl<'tcx> MonoItem<'tcx> {
         !tcx.subst_and_check_impossible_predicates((def_id, &substs))
     }
 
-    pub fn to_string(&self, tcx: TyCtxt<'tcx>, debug: bool) -> String {
-        return match *self {
-            MonoItem::Fn(instance) => to_string_internal(tcx, "fn ", instance, debug),
-            MonoItem::Static(def_id) => {
-                let instance = Instance::new(def_id, tcx.intern_substs(&[]));
-                to_string_internal(tcx, "static ", instance, debug)
-            }
-            MonoItem::GlobalAsm(..) => "global_asm".to_string(),
-        };
-
-        fn to_string_internal<'tcx>(
-            tcx: TyCtxt<'tcx>,
-            prefix: &str,
-            instance: Instance<'tcx>,
-            debug: bool,
-        ) -> String {
-            let mut result = String::with_capacity(32);
-            result.push_str(prefix);
-            let printer = DefPathBasedNames::new(tcx, false, false);
-            printer.push_instance_as_string(instance, &mut result, debug);
-            result
-        }
-    }
-
     pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
         match *self {
             MonoItem::Fn(Instance { def, .. }) => {
@@ -229,6 +204,18 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for MonoItem<'tcx> {
     }
 }
 
+impl<'tcx> fmt::Display for MonoItem<'tcx> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            MonoItem::Fn(instance) => write!(f, "fn {}", instance),
+            MonoItem::Static(def_id) => {
+                write!(f, "static {}", Instance::new(def_id, InternalSubsts::empty()))
+            }
+            MonoItem::GlobalAsm(..) => write!(f, "global_asm"),
+        }
+    }
+}
+
 pub struct CodegenUnit<'tcx> {
     /// A name for this CGU. Incremental compilation requires that
     /// name be unique amongst **all** crates. Therefore, it should

compiler/rustc_middle/src/ty/print/mod.rs

@@ -9,8 +9,6 @@ use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
 mod pretty;
 pub use self::pretty::*;
 
-pub mod obsolete;
-
 // FIXME(eddyb) false positive, the lifetime parameters are used with `P:  Printer<...>`.
 #[allow(unused_lifetimes)]
 pub trait Print<'tcx, P> {