Make "long type" printing type aware

Instead of simple string cutting, use a custom printer to hide parts of
long printed types.

3 files changed, 54 insertions, 24 deletions

diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index ae0f158ede9..a792d2694b3 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -276,28 +276,45 @@ impl<'tcx> InstanceDef<'tcx> {
     }
 }
 
-impl<'tcx> fmt::Display for Instance<'tcx> {
+fn fmt_instance(
+    f: &mut fmt::Formatter<'_>,
+    instance: &Instance<'_>,
+    type_length: rustc_session::Limit,
+) -> fmt::Result {
+    ty::tls::with(|tcx| {
+        let substs = tcx.lift(instance.substs).expect("could not lift for printing");
+
+        let s = FmtPrinter::new_with_limit(tcx, Namespace::ValueNS, type_length)
+            .print_def_path(instance.def_id(), substs)?
+            .into_buffer();
+        f.write_str(&s)
+    })?;
+
+    match instance.def {
+        InstanceDef::Item(_) => Ok(()),
+        InstanceDef::VTableShim(_) => write!(f, " - shim(vtable)"),
+        InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
+        InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
+        InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
+        InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({})", ty),
+        InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
+        InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
+        InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({}))", ty),
+        InstanceDef::CloneShim(_, ty) => write!(f, " - shim({})", ty),
+    }
+}
+
+pub struct ShortInstance<'a, 'tcx>(pub &'a Instance<'tcx>, pub usize);
+
+impl<'a, 'tcx> fmt::Display for ShortInstance<'a, 'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        ty::tls::with(|tcx| {
-            let substs = tcx.lift(self.substs).expect("could not lift for printing");
-            let s = FmtPrinter::new(tcx, Namespace::ValueNS)
-                .print_def_path(self.def_id(), substs)?
-                .into_buffer();
-            f.write_str(&s)
-        })?;
+        fmt_instance(f, self.0, rustc_session::Limit(self.1))
+    }
+}
 
-        match self.def {
-            InstanceDef::Item(_) => Ok(()),
-            InstanceDef::VTableShim(_) => write!(f, " - shim(vtable)"),
-            InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
-            InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
-            InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
-            InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({})", ty),
-            InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
-            InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
-            InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({}))", ty),
-            InstanceDef::CloneShim(_, ty) => write!(f, " - shim({})", ty),
-        }
+impl<'tcx> fmt::Display for Instance<'tcx> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        ty::tls::with(|tcx| fmt_instance(f, self, tcx.type_length_limit()))
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index f9a762261e2..a770c6a2e99 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -84,7 +84,7 @@ pub use self::context::{
     GeneratorInteriorTypeCause, GlobalCtxt, Lift, OnDiskCache, TyCtxt, TypeckResults, UserType,
     UserTypeAnnotationIndex,
 };
-pub use self::instance::{Instance, InstanceDef};
+pub use self::instance::{Instance, InstanceDef, ShortInstance};
 pub use self::list::List;
 pub use self::parameterized::ParameterizedOverTcx;
 pub use self::rvalue_scopes::RvalueScopes;
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 48e803597b0..faa57b437d9 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -13,6 +13,7 @@ use rustc_hir::def_id::{DefId, DefIdSet, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::definitions::{DefPathData, DefPathDataName, DisambiguatedDefPathData};
 use rustc_session::config::TrimmedDefPaths;
 use rustc_session::cstore::{ExternCrate, ExternCrateSource};
+use rustc_session::Limit;
 use rustc_span::symbol::{kw, Ident, Symbol};
 use rustc_target::abi::Size;
 use rustc_target::spec::abi::Abi;
@@ -1583,6 +1584,8 @@ pub struct FmtPrinterData<'a, 'tcx> {
     region_index: usize,
     binder_depth: usize,
     printed_type_count: usize,
+    type_length_limit: Limit,
+    truncated: bool,
 
     pub region_highlight_mode: RegionHighlightMode<'tcx>,
 
@@ -1605,6 +1608,10 @@ impl DerefMut for FmtPrinter<'_, '_> {
 
 impl<'a, 'tcx> FmtPrinter<'a, 'tcx> {
     pub fn new(tcx: TyCtxt<'tcx>, ns: Namespace) -> Self {
+        Self::new_with_limit(tcx, ns, tcx.type_length_limit())
+    }
+
+    pub fn new_with_limit(tcx: TyCtxt<'tcx>, ns: Namespace, type_length_limit: Limit) -> Self {
         FmtPrinter(Box::new(FmtPrinterData {
             tcx,
             // Estimated reasonable capacity to allocate upfront based on a few
@@ -1617,6 +1624,8 @@ impl<'a, 'tcx> FmtPrinter<'a, 'tcx> {
             region_index: 0,
             binder_depth: 0,
             printed_type_count: 0,
+            type_length_limit,
+            truncated: false,
             region_highlight_mode: RegionHighlightMode::new(tcx),
             ty_infer_name_resolver: None,
             const_infer_name_resolver: None,
@@ -1751,12 +1760,16 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
     }
 
     fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
-        let type_length_limit = self.tcx.type_length_limit();
-        if type_length_limit.value_within_limit(self.printed_type_count) {
+        if self.type_length_limit.value_within_limit(self.printed_type_count) {
             self.printed_type_count += 1;
             self.pretty_print_type(ty)
         } else {
-            write!(self, "...")?;
+            self.truncated = true;
+            if let ty::Adt(_, substs) = ty.kind() && substs.len() > 0 {
+                write!(self, "...")?;
+            } else {
+                write!(self, "_")?;
+            }
             Ok(self)
         }
     }