rustc: always hide defaulted generic args, even in verbose mode.

Author: eddyb

src/librustc/ty/print/mod.rs

@@ -1,7 +1,7 @@
 use crate::hir::map::DefPathData;
 use crate::hir::def_id::{CrateNum, DefId};
 use crate::ty::{self, DefIdTree, Ty, TyCtxt};
-use crate::ty::subst::{Subst, SubstsRef};
+use crate::ty::subst::{Kind, Subst, SubstsRef};
 
 use rustc_data_structures::fx::FxHashSet;
 
@@ -129,7 +129,7 @@ pub trait Printer: Sized {
     ) -> Result<Self::Path, Self::Error>;
 }
 
-impl<P: Printer> PrintCx<'a, 'gcx, 'tcx, P> {
+impl<P: Printer> PrintCx<'_, 'gcx, 'tcx, P> {
     pub fn default_print_def_path(
         self,
         def_id: DefId,
@@ -197,8 +197,7 @@ impl<P: Printer> PrintCx<'a, 'gcx, 'tcx, P> {
                 };
 
                 if let (Some(generics), Some(substs)) = (generics, substs) {
-                    let has_own_self = generics.has_self && generics.parent_count == 0;
-                    let params = &generics.params[has_own_self as usize..];
+                    let params = self.generic_params_to_print(generics, substs);
                     self.path_generic_args(print_path, params, substs, projections)
                 } else {
                     print_path(self)
@@ -207,6 +206,30 @@ impl<P: Printer> PrintCx<'a, 'gcx, 'tcx, P> {
         }
     }
 
+    pub fn generic_params_to_print(
+        &self,
+        generics: &'a ty::Generics,
+        substs: SubstsRef<'tcx>,
+    ) -> &'a [ty::GenericParamDef] {
+        // Don't print args for `Self` parameters (of traits).
+        let has_own_self = generics.has_self && generics.parent_count == 0;
+        let params = &generics.params[has_own_self as usize..];
+
+        // Don't print args that are the defaults of their respective parameters.
+        let num_supplied_defaults = params.iter().rev().take_while(|param| {
+            match param.kind {
+                ty::GenericParamDefKind::Lifetime => false,
+                ty::GenericParamDefKind::Type { has_default, .. } => {
+                    has_default && substs[param.index as usize] == Kind::from(
+                        self.tcx.type_of(param.def_id).subst(self.tcx, substs)
+                    )
+                }
+                ty::GenericParamDefKind::Const => false, // FIXME(const_generics:defaults)
+            }
+        }).count();
+        &params[..params.len() - num_supplied_defaults]
+    }
+
     fn default_print_impl_path(
         self,
         impl_def_id: DefId,

src/librustc/ty/print/pretty.rs

@@ -502,25 +502,6 @@ impl<'gcx, 'tcx, P: PrettyPrinter> PrintCx<'_, 'gcx, 'tcx, P> {
                 _ => false,
             }
         });
-
-        // Don't print args that are the defaults of their respective parameters.
-        let num_supplied_defaults = if self.tcx.sess.verbose() {
-            0
-        } else {
-            params.iter().rev().take_while(|param| {
-                match param.kind {
-                    ty::GenericParamDefKind::Lifetime => false,
-                    ty::GenericParamDefKind::Type { has_default, .. } => {
-                        has_default && substs[param.index as usize] == Kind::from(
-                            self.tcx.type_of(param.def_id).subst(self.tcx, substs)
-                        )
-                    }
-                    ty::GenericParamDefKind::Const => false, // FIXME(const_generics:defaults)
-                }
-            }).count()
-        };
-
-        let params = &params[..params.len() - num_supplied_defaults];
         let mut args = params.iter().map(|param| {
             substs[param.index as usize]
         }).filter(|arg| {
@@ -657,8 +638,7 @@ impl<F: fmt::Write> Printer for FmtPrinter<F> {
             })?;
             if visible_path_success {
                 return if let (Some(generics), Some(substs)) = (generics, substs) {
-                    let has_own_self = generics.has_self && generics.parent_count == 0;
-                    let params = &generics.params[has_own_self as usize..];
+                    let params = self.generic_params_to_print(generics, substs);
                     self.path_generic_args(|cx| cx.ok(), params, substs, projections)
                 } else {
                     self.ok()

src/test/ui/substs-ppaux.rs

@@ -25,7 +25,7 @@ fn foo<'z>() where &'z (): Sized {
     let x: () = <i8 as Foo<'static, 'static,  u32>>::bar::<'static, char>;
     //[verbose]~^ ERROR mismatched types
     //[verbose]~| expected type `()`
-    //[verbose]~| found type `fn() {<i8 as Foo<ReStatic, ReStatic, u32>>::bar::<ReStatic, char>}`
+    //[verbose]~| found type `fn() {<i8 as Foo<ReStatic, ReStatic>>::bar::<ReStatic, char>}`
     //[normal]~^^^^ ERROR mismatched types
     //[normal]~| expected type `()`
     //[normal]~| found type `fn() {<i8 as Foo<'static, 'static>>::bar::<'static, char>}`

src/test/ui/substs-ppaux.verbose.stderr

@@ -14,7 +14,7 @@ LL |     let x: () = <i8 as Foo<'static, 'static,  u32>>::bar::<'static, char>;
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found fn item
    |
    = note: expected type `()`
-              found type `fn() {<i8 as Foo<ReStatic, ReStatic, u32>>::bar::<ReStatic, char>}`
+              found type `fn() {<i8 as Foo<ReStatic, ReStatic>>::bar::<ReStatic, char>}`
 
 error[E0308]: mismatched types
   --> $DIR/substs-ppaux.rs:33:17