Merge #8916

8916: ItemTree pretty-printing r=jonas-schievink a=jonas-schievink

This adds a printer for `ItemTree` contents, and a few tests to ensure that `ItemTree` lowering works like we expect it to. It also adds a new "Debug ItemTree" command that can be used to see the `ItemTree` of the currently open file. The pretty-printed output is usually close enough to Rust syntax that we can even use Rust syntax highlighting.

This is similar to the old `ItemTree` tests we had, but produces significantly more readable output, so these should actually carry their weight.

Co-authored-by: Jonas Schievink <[email protected]>

1 files changed, 525 insertions, 0 deletions

diff --git a/crates/hir_def/src/item_tree/pretty.rs b/crates/hir_def/src/item_tree/pretty.rs
new file mode 100644
index 000000000..5ec02d1be
--- /dev/null
+++ b/crates/hir_def/src/item_tree/pretty.rs
@@ -0,0 +1,525 @@
+//! `ItemTree` debug printer.
+
+use std::fmt::{self, Write};
+
+use crate::{attr::RawAttrs, visibility::RawVisibility};
+
+use super::*;
+
+pub(super) fn print_item_tree(tree: &ItemTree) -> String {
+    let mut p = Printer { tree, buf: String::new(), indent_level: 0, needs_indent: true };
+
+    if let Some(attrs) = tree.attrs.get(&AttrOwner::TopLevel) {
+        p.print_attrs(attrs, true);
+    }
+    p.blank();
+
+    for item in tree.top_level_items() {
+        p.print_mod_item(*item);
+    }
+
+    let mut s = p.buf.trim_end_matches('\n').to_string();
+    s.push('\n');
+    s
+}
+
+macro_rules! w {
+    ($dst:expr, $($arg:tt)*) => {
+        drop(write!($dst, $($arg)*))
+    };
+}
+
+macro_rules! wln {
+    ($dst:expr) => {
+        drop(writeln!($dst))
+    };
+    ($dst:expr, $($arg:tt)*) => {
+        drop(writeln!($dst, $($arg)*))
+    };
+}
+
+struct Printer<'a> {
+    tree: &'a ItemTree,
+    buf: String,
+    indent_level: usize,
+    needs_indent: bool,
+}
+
+impl<'a> Printer<'a> {
+    fn indented(&mut self, f: impl FnOnce(&mut Self)) {
+        self.indent_level += 1;
+        wln!(self);
+        f(self);
+        self.indent_level -= 1;
+        self.buf = self.buf.trim_end_matches('\n').to_string();
+    }
+
+    /// Ensures that a blank line is output before the next text.
+    fn blank(&mut self) {
+        let mut iter = self.buf.chars().rev().fuse();
+        match (iter.next(), iter.next()) {
+            (Some('\n'), Some('\n')) | (Some('\n'), None) | (None, None) => {}
+            (Some('\n'), Some(_)) => {
+                self.buf.push('\n');
+            }
+            (Some(_), _) => {
+                self.buf.push('\n');
+                self.buf.push('\n');
+            }
+            (None, Some(_)) => unreachable!(),
+        }
+    }
+
+    fn print_attrs(&mut self, attrs: &RawAttrs, inner: bool) {
+        let inner = if inner { "!" } else { "" };
+        for attr in &**attrs {
+            wln!(
+                self,
+                "#{}[{}{}]  // {:?}",
+                inner,
+                attr.path,
+                attr.input.as_ref().map(|it| it.to_string()).unwrap_or_default(),
+                attr.id,
+            );
+        }
+    }
+
+    fn print_attrs_of(&mut self, of: impl Into<AttrOwner>) {
+        if let Some(attrs) = self.tree.attrs.get(&of.into()) {
+            self.print_attrs(attrs, false);
+        }
+    }
+
+    fn print_visibility(&mut self, vis: RawVisibilityId) {
+        match &self.tree[vis] {
+            RawVisibility::Module(path) => w!(self, "pub({}) ", path),
+            RawVisibility::Public => w!(self, "pub "),
+        };
+    }
+
+    fn print_fields(&mut self, fields: &Fields) {
+        match fields {
+            Fields::Record(fields) => {
+                w!(self, " {{");
+                self.indented(|this| {
+                    for field in fields.clone() {
+                        let Field { visibility, name, type_ref } = &this.tree[field];
+                        this.print_attrs_of(field);
+                        this.print_visibility(*visibility);
+                        w!(this, "{}: ", name);
+                        this.print_type_ref(type_ref);
+                        wln!(this, ",");
+                    }
+                });
+                w!(self, "}}");
+            }
+            Fields::Tuple(fields) => {
+                w!(self, "(");
+                self.indented(|this| {
+                    for field in fields.clone() {
+                        let Field { visibility, name, type_ref } = &this.tree[field];
+                        this.print_attrs_of(field);
+                        this.print_visibility(*visibility);
+                        w!(this, "{}: ", name);
+                        this.print_type_ref(type_ref);
+                        wln!(this, ",");
+                    }
+                });
+                w!(self, ")");
+            }
+            Fields::Unit => {}
+        }
+    }
+
+    fn print_mod_item(&mut self, item: ModItem) {
+        self.print_attrs_of(item);
+
+        match item {
+            ModItem::Import(it) => {
+                let Import { visibility, path, is_glob, alias, ast_id: _, index } = &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "use {}", path);
+                if *is_glob {
+                    w!(self, "::*");
+                }
+                if let Some(alias) = alias {
+                    w!(self, " as {}", alias);
+                }
+                wln!(self, ";  // {}", index);
+            }
+            ModItem::ExternCrate(it) => {
+                let ExternCrate { name, alias, visibility, ast_id: _ } = &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "extern crate {}", name);
+                if let Some(alias) = alias {
+                    w!(self, " as {}", alias);
+                }
+                wln!(self, ";");
+            }
+            ModItem::ExternBlock(it) => {
+                let ExternBlock { abi, ast_id: _, children } = &self.tree[it];
+                w!(self, "extern ");
+                if let Some(abi) = abi {
+                    w!(self, "\"{}\" ", abi);
+                }
+                w!(self, "{{");
+                self.indented(|this| {
+                    for child in &**children {
+                        this.print_mod_item(*child);
+                    }
+                });
+                wln!(self, "}}");
+            }
+            ModItem::Function(it) => {
+                let Function {
+                    name,
+                    visibility,
+                    generic_params: _, // FIXME print these somehow
+                    abi,
+                    params,
+                    ret_type,
+                    ast_id: _,
+                    flags,
+                } = &self.tree[it];
+                if flags.bits != 0 {
+                    wln!(self, "// flags = 0x{:X}", flags.bits);
+                }
+                self.print_visibility(*visibility);
+                if let Some(abi) = abi {
+                    w!(self, "extern \"{}\" ", abi);
+                }
+                w!(self, "fn {}(", name);
+                if !params.is_empty() {
+                    self.indented(|this| {
+                        for param in params.clone() {
+                            this.print_attrs_of(param);
+                            match &this.tree[param] {
+                                Param::Normal(ty) => {
+                                    w!(this, "_: ");
+                                    this.print_type_ref(ty);
+                                    wln!(this, ",");
+                                }
+                                Param::Varargs => {
+                                    wln!(this, "...");
+                                }
+                            };
+                        }
+                    });
+                }
+                w!(self, ") -> ");
+                self.print_type_ref(ret_type);
+                wln!(self, ";");
+            }
+            ModItem::Struct(it) => {
+                let Struct { visibility, name, fields, generic_params: _, ast_id: _ } =
+                    &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "struct {}", name);
+                self.print_fields(fields);
+                if matches!(fields, Fields::Record(_)) {
+                    wln!(self);
+                } else {
+                    wln!(self, ";");
+                }
+            }
+            ModItem::Union(it) => {
+                let Union { name, visibility, fields, generic_params: _, ast_id: _ } =
+                    &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "union {}", name);
+                self.print_fields(fields);
+                if matches!(fields, Fields::Record(_)) {
+                    wln!(self);
+                } else {
+                    wln!(self, ";");
+                }
+            }
+            ModItem::Enum(it) => {
+                let Enum { name, visibility, variants, generic_params: _, ast_id: _ } =
+                    &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "enum {} {{", name);
+                self.indented(|this| {
+                    for variant in variants.clone() {
+                        let Variant { name, fields } = &this.tree[variant];
+                        this.print_attrs_of(variant);
+                        w!(this, "{}", name);
+                        this.print_fields(fields);
+                        wln!(this, ",");
+                    }
+                });
+                wln!(self, "}}");
+            }
+            ModItem::Const(it) => {
+                let Const { name, visibility, type_ref, ast_id: _ } = &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "const ");
+                match name {
+                    Some(name) => w!(self, "{}", name),
+                    None => w!(self, "_"),
+                }
+                w!(self, ": ");
+                self.print_type_ref(type_ref);
+                wln!(self, " = _;");
+            }
+            ModItem::Static(it) => {
+                let Static { name, visibility, mutable, is_extern, type_ref, ast_id: _ } =
+                    &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "static ");
+                if *mutable {
+                    w!(self, "mut ");
+                }
+                w!(self, "{}: ", name);
+                self.print_type_ref(type_ref);
+                w!(self, " = _;");
+                if *is_extern {
+                    w!(self, "  // extern");
+                }
+                wln!(self);
+            }
+            ModItem::Trait(it) => {
+                let Trait {
+                    name,
+                    visibility,
+                    is_auto,
+                    is_unsafe,
+                    bounds,
+                    items,
+                    generic_params: _,
+                    ast_id: _,
+                } = &self.tree[it];
+                self.print_visibility(*visibility);
+                if *is_unsafe {
+                    w!(self, "unsafe ");
+                }
+                if *is_auto {
+                    w!(self, "auto ");
+                }
+                w!(self, "trait {}", name);
+                if !bounds.is_empty() {
+                    w!(self, ": ");
+                    self.print_type_bounds(bounds);
+                }
+                w!(self, " {{");
+                self.indented(|this| {
+                    for item in &**items {
+                        this.print_mod_item((*item).into());
+                    }
+                });
+                wln!(self, "}}");
+            }
+            ModItem::Impl(it) => {
+                let Impl {
+                    target_trait,
+                    self_ty,
+                    is_negative,
+                    items,
+                    generic_params: _,
+                    ast_id: _,
+                } = &self.tree[it];
+                w!(self, "impl ");
+                if *is_negative {
+                    w!(self, "!");
+                }
+                if let Some(tr) = target_trait {
+                    self.print_path(&tr.path);
+                    w!(self, " for ");
+                }
+                self.print_type_ref(self_ty);
+                w!(self, " {{");
+                self.indented(|this| {
+                    for item in &**items {
+                        this.print_mod_item((*item).into());
+                    }
+                });
+                wln!(self, "}}");
+            }
+            ModItem::TypeAlias(it) => {
+                let TypeAlias {
+                    name,
+                    visibility,
+                    bounds,
+                    type_ref,
+                    is_extern,
+                    generic_params: _,
+                    ast_id: _,
+                } = &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "type {}", name);
+                if !bounds.is_empty() {
+                    w!(self, ": ");
+                    self.print_type_bounds(bounds);
+                }
+                if let Some(ty) = type_ref {
+                    w!(self, " = ");
+                    self.print_type_ref(ty);
+                }
+                w!(self, ";");
+                if *is_extern {
+                    w!(self, "  // extern");
+                }
+                wln!(self);
+            }
+            ModItem::Mod(it) => {
+                let Mod { name, visibility, kind, ast_id: _ } = &self.tree[it];
+                self.print_visibility(*visibility);
+                w!(self, "mod {}", name);
+                match kind {
+                    ModKind::Inline { items } => {
+                        w!(self, " {{");
+                        self.indented(|this| {
+                            for item in &**items {
+                                this.print_mod_item((*item).into());
+                            }
+                        });
+                        wln!(self, "}}");
+                    }
+                    ModKind::Outline {} => {
+                        wln!(self, ";");
+                    }
+                }
+            }
+            ModItem::MacroCall(it) => {
+                let MacroCall { path, ast_id: _, fragment: _ } = &self.tree[it];
+                wln!(self, "{}!(...);", path);
+            }
+            ModItem::MacroRules(it) => {
+                let MacroRules { name, ast_id: _ } = &self.tree[it];
+                wln!(self, "macro_rules! {} {{ ... }}", name);
+            }
+            ModItem::MacroDef(it) => {
+                let MacroDef { name, visibility, ast_id: _ } = &self.tree[it];
+                self.print_visibility(*visibility);
+                wln!(self, "macro {} {{ ... }}", name);
+            }
+        }
+
+        self.blank();
+    }
+
+    fn print_type_ref(&mut self, type_ref: &TypeRef) {
+        // FIXME: deduplicate with `HirDisplay` impl
+        match type_ref {
+            TypeRef::Never => w!(self, "!"),
+            TypeRef::Placeholder => w!(self, "_"),
+            TypeRef::Tuple(fields) => {
+                w!(self, "(");
+                for (i, field) in fields.iter().enumerate() {
+                    if i != 0 {
+                        w!(self, ", ");
+                    }
+                    self.print_type_ref(field);
+                }
+                w!(self, ")");
+            }
+            TypeRef::Path(path) => self.print_path(path),
+            TypeRef::RawPtr(pointee, mtbl) => {
+                let mtbl = match mtbl {
+                    Mutability::Shared => "*const",
+                    Mutability::Mut => "*mut",
+                };
+                w!(self, "{} ", mtbl);
+                self.print_type_ref(pointee);
+            }
+            TypeRef::Reference(pointee, lt, mtbl) => {
+                let mtbl = match mtbl {
+                    Mutability::Shared => "",
+                    Mutability::Mut => "mut ",
+                };
+                w!(self, "&");
+                if let Some(lt) = lt {
+                    w!(self, "{} ", lt.name);
+                }
+                w!(self, "{}", mtbl);
+                self.print_type_ref(pointee);
+            }
+            TypeRef::Array(elem, len) => {
+                w!(self, "[");
+                self.print_type_ref(elem);
+                w!(self, "; {}]", len);
+            }
+            TypeRef::Slice(elem) => {
+                w!(self, "[");
+                self.print_type_ref(elem);
+                w!(self, "]");
+            }
+            TypeRef::Fn(args_and_ret, varargs) => {
+                let (ret, args) =
+                    args_and_ret.split_last().expect("TypeRef::Fn is missing return type");
+                w!(self, "fn(");
+                for (i, arg) in args.iter().enumerate() {
+                    if i != 0 {
+                        w!(self, ", ");
+                    }
+                    self.print_type_ref(arg);
+                }
+                if *varargs {
+                    if !args.is_empty() {
+                        w!(self, ", ");
+                    }
+                    w!(self, "...");
+                }
+                w!(self, ") -> ");
+                self.print_type_ref(ret);
+            }
+            TypeRef::Macro(_ast_id) => {
+                w!(self, "<macro>");
+            }
+            TypeRef::Error => drop(write!(self, "{{unknown}}")),
+            TypeRef::ImplTrait(bounds) => {
+                w!(self, "impl ");
+                self.print_type_bounds(bounds);
+            }
+            TypeRef::DynTrait(bounds) => {
+                w!(self, "dyn ");
+                self.print_type_bounds(bounds);
+            }
+        }
+    }
+
+    fn print_type_bounds(&mut self, bounds: &[TypeBound]) {
+        for (i, bound) in bounds.iter().enumerate() {
+            if i != 0 {
+                w!(self, " + ");
+            }
+
+            match bound {
+                TypeBound::Path(path) => self.print_path(path),
+                TypeBound::Lifetime(lt) => w!(self, "{}", lt.name),
+                TypeBound::Error => w!(self, "{{unknown}}"),
+            }
+        }
+    }
+
+    fn print_path(&mut self, path: &Path) {
+        if path.type_anchor().is_none()
+            && path.segments().iter().all(|seg| seg.args_and_bindings.is_none())
+        {
+            w!(self, "{}", path.mod_path());
+        } else {
+            // too complicated, just use `Debug`
+            w!(self, "{:?}", path);
+        }
+    }
+}
+
+impl<'a> Write for Printer<'a> {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        for line in s.split_inclusive('\n') {
+            if self.needs_indent {
+                match self.buf.chars().last() {
+                    Some('\n') | None => {}
+                    _ => self.buf.push('\n'),
+                }
+                self.buf.push_str(&"    ".repeat(self.indent_level));
+                self.needs_indent = false;
+            }
+
+            self.buf.push_str(line);
+            self.needs_indent = line.ends_with('\n');
+        }
+
+        Ok(())
+    }
+}