Auto merge of rust-lang#85269 - dpaoliello:dpaoliello/DebugSymbols, r=michaelwoerister

Improve debug symbol names to avoid ambiguity and work better with MSVC's debugger

There are several cases where names of types and functions in the debug info are either ambiguous, or not helpful, such as including ambiguous placeholders (e.g., `{{impl}}`, `{{closure}}` or `dyn _'`) or dropping qualifications (e.g., for dynamic types).

Instead, each debug symbol name should be unique and useful:
* Include disambiguators for anonymous `DefPathDataName` (closures and generators), and unify their formatting when used as a path-qualifier vs item being qualified.
* Qualify the principal trait for dynamic types.
* If there is no principal trait for a dynamic type, emit all other traits instead.
* Respect the `qualified` argument when emitting ref and pointer types.
* For implementations, emit the disambiguator.
* Print const generics when emitting generic parameters or arguments.

Additionally, when targeting MSVC, its debugger treats many command arguments as C++ expressions, even when the argument is defined to be a symbol name. As such names in the debug info need to be more C++-like to be parsed correctly:
* Avoid characters with special meaning (`#`, `[`, `"`, `+`).
* Never start a name with `<` or `{` as this is treated as an operator.
* `>>` is always treated as a right-shift, even when parsing generic arguments (so add a space to avoid this).
* Emit function declarations using C/C++ style syntax (e.g., leading return type).
* Emit arrays as a synthetic `array$<type, size>` type.
* Include a `$` in all synthetic types as this is a legal character for C++, but not Rust (thus we avoid collisions with user types).

Author: bors

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -471,21 +471,28 @@ fn trait_pointer_metadata(
     // type is assigned the correct name, size, namespace, and source location.
     // However, it does not describe the trait's methods.
 
-    let containing_scope = match trait_type.kind() {
-        ty::Dynamic(ref data, ..) => {
-            data.principal_def_id().map(|did| get_namespace_for_item(cx, did))
-        }
-        _ => {
-            bug!(
-                "debuginfo: unexpected trait-object type in \
-                  trait_pointer_metadata(): {:?}",
-                trait_type
-            );
-        }
-    };
+    let (containing_scope, trait_type_name) = match trait_object_type {
+        Some(trait_object_type) => match trait_object_type.kind() {
+            ty::Adt(def, _) => (
+                Some(get_namespace_for_item(cx, def.did)),
+                compute_debuginfo_type_name(cx.tcx, trait_object_type, false),
+            ),
+            ty::RawPtr(_) | ty::Ref(..) => {
+                (NO_SCOPE_METADATA, compute_debuginfo_type_name(cx.tcx, trait_object_type, true))
+            }
+            _ => {
+                bug!(
+                    "debuginfo: unexpected trait-object type in \
+                      trait_pointer_metadata(): {:?}",
+                    trait_object_type
+                );
+            }
+        },
 
-    let trait_object_type = trait_object_type.unwrap_or(trait_type);
-    let trait_type_name = compute_debuginfo_type_name(cx.tcx, trait_object_type, false);
+        // No object type, use the trait type directly (no scope here since the type
+        // will be wrapped in the dyn$ synthetic type).
+        None => (NO_SCOPE_METADATA, compute_debuginfo_type_name(cx.tcx, trait_type, true)),
+    };
 
     let file_metadata = unknown_file_metadata(cx);
 
@@ -525,7 +532,7 @@ fn trait_pointer_metadata(
 
     composite_type_metadata(
         cx,
-        trait_object_type,
+        trait_object_type.unwrap_or(trait_type),
         &trait_type_name[..],
         unique_type_id,
         member_descriptions,

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -5,7 +5,6 @@ use rustc_codegen_ssa::mir::debuginfo::VariableKind::*;
 use self::metadata::{file_metadata, type_metadata, TypeMap};
 use self::metadata::{UNKNOWN_COLUMN_NUMBER, UNKNOWN_LINE_NUMBER};
 use self::namespace::mangled_name_of_instance;
-use self::type_names::compute_debuginfo_type_name;
 use self::utils::{create_DIArray, is_node_local_to_unit, DIB};
 
 use crate::abi::FnAbi;
@@ -311,10 +310,10 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             llvm::LLVMRustDIBuilderCreateSubroutineType(DIB(self), fn_signature)
         };
 
-        // Find the enclosing function, in case this is a closure.
-        let def_key = self.tcx().def_key(def_id);
-        let mut name = def_key.disambiguated_data.data.to_string();
+        let mut name = String::new();
+        type_names::push_item_name(self.tcx(), def_id, false, &mut name);
 
+        // Find the enclosing function, in case this is a closure.
         let enclosing_fn_def_id = self.tcx().closure_base_def_id(def_id);
 
         // Get_template_parameters() will append a `<...>` clause to the function
@@ -428,24 +427,16 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             substs: SubstsRef<'tcx>,
             name_to_append_suffix_to: &mut String,
         ) -> &'ll DIArray {
+            type_names::push_generic_params(
+                cx.tcx,
+                cx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), substs),
+                name_to_append_suffix_to,
+            );
+
             if substs.types().next().is_none() {
                 return create_DIArray(DIB(cx), &[]);
             }
 
-            name_to_append_suffix_to.push('<');
-            for (i, actual_type) in substs.types().enumerate() {
-                if i != 0 {
-                    name_to_append_suffix_to.push(',');
-                }
-
-                let actual_type =
-                    cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), actual_type);
-                // Add actual type name to <...> clause of function name
-                let actual_type_name = compute_debuginfo_type_name(cx.tcx(), actual_type, true);
-                name_to_append_suffix_to.push_str(&actual_type_name[..]);
-            }
-            name_to_append_suffix_to.push('>');
-
             // Again, only create type information if full debuginfo is enabled
             let template_params: Vec<_> = if cx.sess().opts.debuginfo == DebugInfo::Full {
                 let names = get_parameter_names(cx, generics);

compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs

@@ -1,13 +1,13 @@
 // Namespace Handling.
 
 use super::utils::{debug_context, DIB};
+use rustc_codegen_ssa::debuginfo::type_names;
 use rustc_middle::ty::{self, Instance};
 
 use crate::common::CodegenCx;
 use crate::llvm;
 use crate::llvm::debuginfo::DIScope;
 use rustc_hir::def_id::DefId;
-use rustc_hir::definitions::DefPathData;
 
 pub fn mangled_name_of_instance<'a, 'tcx>(
     cx: &CodegenCx<'a, 'tcx>,
@@ -27,25 +27,18 @@ pub fn item_namespace(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'ll DIScope {
         .parent
         .map(|parent| item_namespace(cx, DefId { krate: def_id.krate, index: parent }));
 
-    let crate_name_as_str;
-    let name_to_string;
-    let namespace_name = match def_key.disambiguated_data.data {
-        DefPathData::CrateRoot => {
-            crate_name_as_str = cx.tcx.crate_name(def_id.krate).as_str();
-            &*crate_name_as_str
-        }
-        data => {
-            name_to_string = data.to_string();
-            &*name_to_string
-        }
+    let namespace_name_string = {
+        let mut output = String::new();
+        type_names::push_item_name(cx.tcx, def_id, false, &mut output);
+        output
     };
 
     let scope = unsafe {
         llvm::LLVMRustDIBuilderCreateNameSpace(
             DIB(cx),
             parent_scope,
-            namespace_name.as_ptr().cast(),
-            namespace_name.len(),
+            namespace_name_string.as_ptr().cast(),
+            namespace_name_string.len(),
             false, // ExportSymbols (only relevant for C++ anonymous namespaces)
         )
     };