Merge #1110

1110: Introduce display module and implement new FunctionSignature for CallInfo's r=matklad a=vipentti

This introduces a new module `display` in `ra_ide_api` that contains UI-related things, in addition this refactors CallInfo's function signatures into a new `FunctionSignature` type, which implements `Display` and can be converted into `lsp_types::SignatureInformation` in the `conv` layer. 

Currently only `CallInfo` uses the `FunctionSignature` directly, but `function_label` now uses the same signature and returns it as a string, using the `Display` implementation.

This also fixes #960 

I think this similar structure could be applied to other UI-displayable items, so instead of the `ra_ide_api` returning `Strings` we could return some intermediate structures that can be converted into a UI-displayable `String` easily, but that could also provide some additional information.

Co-authored-by: Ville Penttinen <[email protected]>

4 files changed, 802 insertions, 0 deletions

diff --git a/crates/ra_ide_api/src/display/function_signature.rs b/crates/ra_ide_api/src/display/function_signature.rs
new file mode 100644
index 000000000..d09950bce
--- /dev/null
+++ b/crates/ra_ide_api/src/display/function_signature.rs
@@ -0,0 +1,101 @@
+use super::{where_predicates, generic_parameters};
+use crate::db;
+use std::fmt::{self, Display};
+use join_to_string::join;
+use ra_syntax::ast::{self, AstNode, NameOwner, VisibilityOwner};
+use std::convert::From;
+use hir::{Docs, Documentation};
+
+/// Contains information about a function signature
+#[derive(Debug)]
+pub struct FunctionSignature {
+    /// Optional visibility
+    pub visibility: Option<String>,
+    /// Name of the function
+    pub name: Option<String>,
+    /// Documentation for the function
+    pub doc: Option<Documentation>,
+    /// Generic parameters
+    pub generic_parameters: Vec<String>,
+    /// Parameters of the function
+    pub parameters: Vec<String>,
+    /// Optional return type
+    pub ret_type: Option<String>,
+    /// Where predicates
+    pub where_predicates: Vec<String>,
+}
+
+impl FunctionSignature {
+    pub(crate) fn with_doc_opt(mut self, doc: Option<Documentation>) -> Self {
+        self.doc = doc;
+        self
+    }
+
+    pub(crate) fn from_hir(db: &db::RootDatabase, function: hir::Function) -> Self {
+        let doc = function.docs(db);
+        let (_, ast_node) = function.source(db);
+        FunctionSignature::from(&*ast_node).with_doc_opt(doc)
+    }
+}
+
+impl From<&'_ ast::FnDef> for FunctionSignature {
+    fn from(node: &ast::FnDef) -> FunctionSignature {
+        fn param_list(node: &ast::FnDef) -> Vec<String> {
+            let mut res = vec![];
+            if let Some(param_list) = node.param_list() {
+                if let Some(self_param) = param_list.self_param() {
+                    res.push(self_param.syntax().text().to_string())
+                }
+
+                res.extend(param_list.params().map(|param| param.syntax().text().to_string()));
+            }
+            res
+        }
+
+        FunctionSignature {
+            visibility: node.visibility().map(|n| n.syntax().text().to_string()),
+            name: node.name().map(|n| n.text().to_string()),
+            ret_type: node
+                .ret_type()
+                .and_then(|r| r.type_ref())
+                .map(|n| n.syntax().text().to_string()),
+            parameters: param_list(node),
+            generic_parameters: generic_parameters(node),
+            where_predicates: where_predicates(node),
+            // docs are processed separately
+            doc: None,
+        }
+    }
+}
+
+impl Display for FunctionSignature {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if let Some(t) = &self.visibility {
+            write!(f, "{} ", t)?;
+        }
+
+        if let Some(name) = &self.name {
+            write!(f, "fn {}", name)?;
+        }
+
+        if !self.generic_parameters.is_empty() {
+            join(self.generic_parameters.iter())
+                .separator(", ")
+                .surround_with("<", ">")
+                .to_fmt(f)?;
+        }
+
+        join(self.parameters.iter()).separator(", ").surround_with("(", ")").to_fmt(f)?;
+
+        if let Some(t) = &self.ret_type {
+            write!(f, " -> {}", t)?;
+        }
+
+        if !self.where_predicates.is_empty() {
+            write!(f, "\nwhere ")?;
+            join(self.where_predicates.iter()).separator(",\n      ").to_fmt(f)?;
+        }
+
+        Ok(())
+    }
+}
diff --git a/crates/ra_ide_api/src/display/navigation_target.rs b/crates/ra_ide_api/src/display/navigation_target.rs
new file mode 100644
index 000000000..3c518faf5
--- /dev/null
+++ b/crates/ra_ide_api/src/display/navigation_target.rs
@@ -0,0 +1,329 @@
+use ra_db::{FileId, SourceDatabase};
+use ra_syntax::{
+    SyntaxNode, SyntaxNodePtr, AstNode, SmolStr, TextRange, TreeArc,
+    SyntaxKind::{self, NAME},
+    ast::{self, NameOwner, VisibilityOwner, TypeAscriptionOwner},
+    algo::visit::{visitor, Visitor},
+};
+use hir::{ModuleSource, FieldSource, Name, ImplItem};
+
+use crate::{FileSymbol, db::RootDatabase};
+
+/// `NavigationTarget` represents and element in the editor's UI which you can
+/// click on to navigate to a particular piece of code.
+///
+/// Typically, a `NavigationTarget` corresponds to some element in the source
+/// code, like a function or a struct, but this is not strictly required.
+#[derive(Debug, Clone)]
+pub struct NavigationTarget {
+    file_id: FileId,
+    name: SmolStr,
+    kind: SyntaxKind,
+    full_range: TextRange,
+    focus_range: Option<TextRange>,
+    container_name: Option<SmolStr>,
+}
+
+impl NavigationTarget {
+    /// When `focus_range` is specified, returns it. otherwise
+    /// returns `full_range`
+    pub fn range(&self) -> TextRange {
+        self.focus_range.unwrap_or(self.full_range)
+    }
+
+    pub fn name(&self) -> &SmolStr {
+        &self.name
+    }
+
+    pub fn container_name(&self) -> Option<&SmolStr> {
+        self.container_name.as_ref()
+    }
+
+    pub fn kind(&self) -> SyntaxKind {
+        self.kind
+    }
+
+    pub fn file_id(&self) -> FileId {
+        self.file_id
+    }
+
+    pub fn full_range(&self) -> TextRange {
+        self.full_range
+    }
+
+    /// A "most interesting" range withing the `full_range`.
+    ///
+    /// Typically, `full_range` is the whole syntax node,
+    /// including doc comments, and `focus_range` is the range of the identifier.
+    pub fn focus_range(&self) -> Option<TextRange> {
+        self.focus_range
+    }
+
+    pub(crate) fn from_bind_pat(file_id: FileId, pat: &ast::BindPat) -> NavigationTarget {
+        NavigationTarget::from_named(file_id, pat)
+    }
+
+    pub(crate) fn from_symbol(symbol: FileSymbol) -> NavigationTarget {
+        NavigationTarget {
+            file_id: symbol.file_id,
+            name: symbol.name.clone(),
+            kind: symbol.ptr.kind(),
+            full_range: symbol.ptr.range(),
+            focus_range: symbol.name_range,
+            container_name: symbol.container_name.clone(),
+        }
+    }
+
+    pub(crate) fn from_scope_entry(
+        file_id: FileId,
+        name: Name,
+        ptr: SyntaxNodePtr,
+    ) -> NavigationTarget {
+        NavigationTarget {
+            file_id,
+            name: name.to_string().into(),
+            full_range: ptr.range(),
+            focus_range: None,
+            kind: NAME,
+            container_name: None,
+        }
+    }
+
+    pub(crate) fn from_module(db: &RootDatabase, module: hir::Module) -> NavigationTarget {
+        let (file_id, source) = module.definition_source(db);
+        let file_id = file_id.as_original_file();
+        let name = module.name(db).map(|it| it.to_string().into()).unwrap_or_default();
+        match source {
+            ModuleSource::SourceFile(node) => {
+                NavigationTarget::from_syntax(file_id, name, None, node.syntax())
+            }
+            ModuleSource::Module(node) => {
+                NavigationTarget::from_syntax(file_id, name, None, node.syntax())
+            }
+        }
+    }
+
+    pub(crate) fn from_module_to_decl(db: &RootDatabase, module: hir::Module) -> NavigationTarget {
+        let name = module.name(db).map(|it| it.to_string().into()).unwrap_or_default();
+        if let Some((file_id, source)) = module.declaration_source(db) {
+            let file_id = file_id.as_original_file();
+            return NavigationTarget::from_syntax(file_id, name, None, source.syntax());
+        }
+        NavigationTarget::from_module(db, module)
+    }
+
+    pub(crate) fn from_function(db: &RootDatabase, func: hir::Function) -> NavigationTarget {
+        let (file_id, fn_def) = func.source(db);
+        NavigationTarget::from_named(file_id.original_file(db), &*fn_def)
+    }
+
+    pub(crate) fn from_field(db: &RootDatabase, field: hir::StructField) -> NavigationTarget {
+        let (file_id, field) = field.source(db);
+        let file_id = file_id.original_file(db);
+        match field {
+            FieldSource::Named(it) => NavigationTarget::from_named(file_id, &*it),
+            FieldSource::Pos(it) => {
+                NavigationTarget::from_syntax(file_id, "".into(), None, it.syntax())
+            }
+        }
+    }
+
+    pub(crate) fn from_adt_def(db: &RootDatabase, adt_def: hir::AdtDef) -> NavigationTarget {
+        match adt_def {
+            hir::AdtDef::Struct(s) => {
+                let (file_id, node) = s.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+            hir::AdtDef::Enum(s) => {
+                let (file_id, node) = s.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+        }
+    }
+
+    pub(crate) fn from_def(db: &RootDatabase, module_def: hir::ModuleDef) -> NavigationTarget {
+        match module_def {
+            hir::ModuleDef::Module(module) => NavigationTarget::from_module(db, module),
+            hir::ModuleDef::Function(func) => NavigationTarget::from_function(db, func),
+            hir::ModuleDef::Struct(s) => {
+                let (file_id, node) = s.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+            hir::ModuleDef::Const(s) => {
+                let (file_id, node) = s.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+            hir::ModuleDef::Static(s) => {
+                let (file_id, node) = s.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+            hir::ModuleDef::Enum(e) => {
+                let (file_id, node) = e.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+            hir::ModuleDef::EnumVariant(var) => {
+                let (file_id, node) = var.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+            hir::ModuleDef::Trait(e) => {
+                let (file_id, node) = e.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+            hir::ModuleDef::TypeAlias(e) => {
+                let (file_id, node) = e.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+        }
+    }
+
+    pub(crate) fn from_impl_block(
+        db: &RootDatabase,
+        impl_block: hir::ImplBlock,
+    ) -> NavigationTarget {
+        let (file_id, node) = impl_block.source(db);
+        NavigationTarget::from_syntax(
+            file_id.as_original_file(),
+            "impl".into(),
+            None,
+            node.syntax(),
+        )
+    }
+
+    pub(crate) fn from_impl_item(db: &RootDatabase, impl_item: hir::ImplItem) -> NavigationTarget {
+        match impl_item {
+            ImplItem::Method(f) => NavigationTarget::from_function(db, f),
+            ImplItem::Const(c) => {
+                let (file_id, node) = c.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+            ImplItem::TypeAlias(a) => {
+                let (file_id, node) = a.source(db);
+                NavigationTarget::from_named(file_id.original_file(db), &*node)
+            }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn assert_match(&self, expected: &str) {
+        let actual = self.debug_render();
+        test_utils::assert_eq_text!(expected.trim(), actual.trim(),);
+    }
+
+    #[cfg(test)]
+    pub(crate) fn debug_render(&self) -> String {
+        let mut buf = format!(
+            "{} {:?} {:?} {:?}",
+            self.name(),
+            self.kind(),
+            self.file_id(),
+            self.full_range()
+        );
+        if let Some(focus_range) = self.focus_range() {
+            buf.push_str(&format!(" {:?}", focus_range))
+        }
+        if let Some(container_name) = self.container_name() {
+            buf.push_str(&format!(" {}", container_name))
+        }
+        buf
+    }
+
+    /// Allows `NavigationTarget` to be created from a `NameOwner`
+    pub(crate) fn from_named(file_id: FileId, node: &impl ast::NameOwner) -> NavigationTarget {
+        let name = node.name().map(|it| it.text().clone()).unwrap_or_default();
+        let focus_range = node.name().map(|it| it.syntax().range());
+        NavigationTarget::from_syntax(file_id, name, focus_range, node.syntax())
+    }
+
+    fn from_syntax(
+        file_id: FileId,
+        name: SmolStr,
+        focus_range: Option<TextRange>,
+        node: &SyntaxNode,
+    ) -> NavigationTarget {
+        NavigationTarget {
+            file_id,
+            name,
+            kind: node.kind(),
+            full_range: node.range(),
+            focus_range,
+            // ptr: Some(LocalSyntaxPtr::new(node)),
+            container_name: None,
+        }
+    }
+
+    pub(crate) fn node(&self, db: &RootDatabase) -> Option<TreeArc<SyntaxNode>> {
+        let source_file = db.parse(self.file_id());
+        let source_file = source_file.syntax();
+        let node = source_file
+            .descendants()
+            .find(|node| node.kind() == self.kind() && node.range() == self.full_range())?
+            .to_owned();
+        Some(node)
+    }
+
+    pub(crate) fn docs(&self, db: &RootDatabase) -> Option<String> {
+        let node = self.node(db)?;
+        fn doc_comments<N: ast::DocCommentsOwner>(node: &N) -> Option<String> {
+            node.doc_comment_text()
+        }
+
+        visitor()
+            .visit(doc_comments::<ast::FnDef>)
+            .visit(doc_comments::<ast::StructDef>)
+            .visit(doc_comments::<ast::EnumDef>)
+            .visit(doc_comments::<ast::TraitDef>)
+            .visit(doc_comments::<ast::Module>)
+            .visit(doc_comments::<ast::TypeAliasDef>)
+            .visit(doc_comments::<ast::ConstDef>)
+            .visit(doc_comments::<ast::StaticDef>)
+            .visit(doc_comments::<ast::NamedFieldDef>)
+            .visit(doc_comments::<ast::EnumVariant>)
+            .accept(&node)?
+    }
+
+    /// Get a description of this node.
+    ///
+    /// e.g. `struct Name`, `enum Name`, `fn Name`
+    pub(crate) fn description(&self, db: &RootDatabase) -> Option<String> {
+        // FIXME: After type inference is done, add type information to improve the output
+        let node = self.node(db)?;
+
+        fn visit_ascribed_node<T>(node: &T, prefix: &str) -> Option<String>
+        where
+            T: NameOwner + VisibilityOwner + TypeAscriptionOwner,
+        {
+            let mut string = visit_node(node, prefix)?;
+
+            if let Some(type_ref) = node.ascribed_type() {
+                string.push_str(": ");
+                type_ref.syntax().text().push_to(&mut string);
+            }
+
+            Some(string)
+        }
+
+        fn visit_node<T>(node: &T, label: &str) -> Option<String>
+        where
+            T: NameOwner + VisibilityOwner,
+        {
+            let mut string =
+                node.visibility().map(|v| format!("{} ", v.syntax().text())).unwrap_or_default();
+            string.push_str(label);
+            string.push_str(node.name()?.text().as_str());
+            Some(string)
+        }
+
+        visitor()
+            .visit(|node: &ast::FnDef| Some(crate::display::function_label(node)))
+            .visit(|node: &ast::StructDef| visit_node(node, "struct "))
+            .visit(|node: &ast::EnumDef| visit_node(node, "enum "))
+            .visit(|node: &ast::TraitDef| visit_node(node, "trait "))
+            .visit(|node: &ast::Module| visit_node(node, "mod "))
+            .visit(|node: &ast::TypeAliasDef| visit_node(node, "type "))
+            .visit(|node: &ast::ConstDef| visit_ascribed_node(node, "const "))
+            .visit(|node: &ast::StaticDef| visit_ascribed_node(node, "static "))
+            .visit(|node: &ast::NamedFieldDef| visit_ascribed_node(node, ""))
+            .visit(|node: &ast::EnumVariant| Some(node.name()?.text().to_string()))
+            .accept(&node)?
+    }
+}
diff --git a/crates/ra_ide_api/src/display/snapshots/tests__file_structure.snap b/crates/ra_ide_api/src/display/snapshots/tests__file_structure.snap
new file mode 100644
index 000000000..32dd99484
--- /dev/null
+++ b/crates/ra_ide_api/src/display/snapshots/tests__file_structure.snap
@@ -0,0 +1,182 @@
+---
+created: "2019-04-08T09:44:50.196004400Z"
+creator: [email protected]
+source: crates/ra_ide_api/src/display/structure.rs
+expression: structure
+---
+[
+    StructureNode {
+        parent: None,
+        label: "Foo",
+        navigation_range: [8; 11),
+        node_range: [1; 26),
+        kind: STRUCT_DEF,
+        detail: None,
+        deprecated: false
+    },
+    StructureNode {
+        parent: Some(
+            0
+        ),
+        label: "x",
+        navigation_range: [18; 19),
+        node_range: [18; 24),
+        kind: NAMED_FIELD_DEF,
+        detail: Some(
+            "i32"
+        ),
+        deprecated: false
+    },
+    StructureNode {
+        parent: None,
+        label: "m",
+        navigation_range: [32; 33),
+        node_range: [28; 158),
+        kind: MODULE,
+        detail: None,
+        deprecated: false
+    },
+    StructureNode {
+        parent: Some(
+            2
+        ),
+        label: "bar1",
+        navigation_range: [43; 47),
+        node_range: [40; 52),
+        kind: FN_DEF,
+        detail: Some(
+            "fn()"
+        ),
+        deprecated: false
+    },
+    StructureNode {
+        parent: Some(
+            2
+        ),
+        label: "bar2",
+        navigation_range: [60; 64),
+        node_range: [57; 81),
+        kind: FN_DEF,
+        detail: Some(
+            "fn<T>(t: T) -> T"
+        ),
+        deprecated: false
+    },
+    StructureNode {
+        parent: Some(
+            2
+        ),
+        label: "bar3",
+        navigation_range: [89; 93),
+        node_range: [86; 156),
+        kind: FN_DEF,
+        detail: Some(
+            "fn<A, B>(a: A, b: B) -> Vec< u32 >"
+        ),
+        deprecated: false
+    },
+    StructureNode {
+        parent: None,
+        label: "E",
+        navigation_range: [165; 166),
+        node_range: [160; 180),
+        kind: ENUM_DEF,
+        detail: None,
+        deprecated: false
+    },
+    StructureNode {
+        parent: Some(
+            6
+        ),
+        label: "X",
+        navigation_range: [169; 170),
+        node_range: [169; 170),
+        kind: ENUM_VARIANT,
+        detail: None,
+        deprecated: false
+    },
+    StructureNode {
+        parent: Some(
+            6
+        ),
+        label: "Y",
+        navigation_range: [172; 173),
+        node_range: [172; 178),
+        kind: ENUM_VARIANT,
+        detail: None,
+        deprecated: false
+    },
+    StructureNode {
+        parent: None,
+        label: "T",
+        navigation_range: [186; 187),
+        node_range: [181; 193),
+        kind: TYPE_ALIAS_DEF,
+        detail: Some(
+            "()"
+        ),
+        deprecated: false
+    },
+    StructureNode {
+        parent: None,
+        label: "S",
+        navigation_range: [201; 202),
+        node_range: [194; 213),
+        kind: STATIC_DEF,
+        detail: Some(
+            "i32"
+        ),
+        deprecated: false
+    },
+    StructureNode {
+        parent: None,
+        label: "C",
+        navigation_range: [220; 221),
+        node_range: [214; 232),
+        kind: CONST_DEF,
+        detail: Some(
+            "i32"
+        ),
+        deprecated: false
+    },
+    StructureNode {
+        parent: None,
+        label: "impl E",
+        navigation_range: [239; 240),
+        node_range: [234; 243),
+        kind: IMPL_BLOCK,
+        detail: None,
+        deprecated: false
+    },
+    StructureNode {
+        parent: None,
+        label: "impl fmt::Debug for E",
+        navigation_range: [265; 266),
+        node_range: [245; 269),
+        kind: IMPL_BLOCK,
+        detail: None,
+        deprecated: false
+    },
+    StructureNode {
+        parent: None,
+        label: "obsolete",
+        navigation_range: [288; 296),
+        node_range: [271; 301),
+        kind: FN_DEF,
+        detail: Some(
+            "fn()"
+        ),
+        deprecated: true
+    },
+    StructureNode {
+        parent: None,
+        label: "very_obsolete",
+        navigation_range: [341; 354),
+        node_range: [303; 359),
+        kind: FN_DEF,
+        detail: Some(
+            "fn()"
+        ),
+        deprecated: true
+    }
+]
diff --git a/crates/ra_ide_api/src/display/structure.rs b/crates/ra_ide_api/src/display/structure.rs
new file mode 100644
index 000000000..ec2c9bbc6
--- /dev/null
+++ b/crates/ra_ide_api/src/display/structure.rs
@@ -0,0 +1,190 @@
+use crate::TextRange;
+
+use ra_syntax::{
+    algo::visit::{visitor, Visitor},
+    ast::{self, AttrsOwner, NameOwner, TypeParamsOwner, TypeAscriptionOwner},
+    AstNode, SourceFile, SyntaxKind, SyntaxNode, WalkEvent,
+};
+
+#[derive(Debug, Clone)]
+pub struct StructureNode {
+    pub parent: Option<usize>,
+    pub label: String,
+    pub navigation_range: TextRange,
+    pub node_range: TextRange,
+    pub kind: SyntaxKind,
+    pub detail: Option<String>,
+    pub deprecated: bool,
+}
+
+pub fn file_structure(file: &SourceFile) -> Vec<StructureNode> {
+    let mut res = Vec::new();
+    let mut stack = Vec::new();
+
+    for event in file.syntax().preorder() {
+        match event {
+            WalkEvent::Enter(node) => {
+                if let Some(mut symbol) = structure_node(node) {
+                    symbol.parent = stack.last().map(|&n| n);
+                    stack.push(res.len());
+                    res.push(symbol);
+                }
+            }
+            WalkEvent::Leave(node) => {
+                if structure_node(node).is_some() {
+                    stack.pop().unwrap();
+                }
+            }
+        }
+    }
+    res
+}
+
+fn structure_node(node: &SyntaxNode) -> Option<StructureNode> {
+    fn decl<N: NameOwner + AttrsOwner>(node: &N) -> Option<StructureNode> {
+        decl_with_detail(node, None)
+    }
+
+    fn decl_with_ascription<N: NameOwner + AttrsOwner + TypeAscriptionOwner>(
+        node: &N,
+    ) -> Option<StructureNode> {
+        decl_with_type_ref(node, node.ascribed_type())
+    }
+
+    fn decl_with_type_ref<N: NameOwner + AttrsOwner>(
+        node: &N,
+        type_ref: Option<&ast::TypeRef>,
+    ) -> Option<StructureNode> {
+        let detail = type_ref.map(|type_ref| {
+            let mut detail = String::new();
+            collapse_ws(type_ref.syntax(), &mut detail);
+            detail
+        });
+        decl_with_detail(node, detail)
+    }
+
+    fn decl_with_detail<N: NameOwner + AttrsOwner>(
+        node: &N,
+        detail: Option<String>,
+    ) -> Option<StructureNode> {
+        let name = node.name()?;
+
+        Some(StructureNode {
+            parent: None,
+            label: name.text().to_string(),
+            navigation_range: name.syntax().range(),
+            node_range: node.syntax().range(),
+            kind: node.syntax().kind(),
+            detail,
+            deprecated: node.attrs().filter_map(|x| x.as_named()).any(|x| x == "deprecated"),
+        })
+    }
+
+    fn collapse_ws(node: &SyntaxNode, output: &mut String) {
+        let mut can_insert_ws = false;
+        for line in node.text().chunks().flat_map(|chunk| chunk.lines()) {
+            let line = line.trim();
+            if line.is_empty() {
+                if can_insert_ws {
+                    output.push_str(" ");
+                    can_insert_ws = false;
+                }
+            } else {
+                output.push_str(line);
+                can_insert_ws = true;
+            }
+        }
+    }
+
+    visitor()
+        .visit(|fn_def: &ast::FnDef| {
+            let mut detail = String::from("fn");
+            if let Some(type_param_list) = fn_def.type_param_list() {
+                collapse_ws(type_param_list.syntax(), &mut detail);
+            }
+            if let Some(param_list) = fn_def.param_list() {
+                collapse_ws(param_list.syntax(), &mut detail);
+            }
+            if let Some(ret_type) = fn_def.ret_type() {
+                detail.push_str(" ");
+                collapse_ws(ret_type.syntax(), &mut detail);
+            }
+
+            decl_with_detail(fn_def, Some(detail))
+        })
+        .visit(decl::<ast::StructDef>)
+        .visit(decl::<ast::EnumDef>)
+        .visit(decl::<ast::EnumVariant>)
+        .visit(decl::<ast::TraitDef>)
+        .visit(decl::<ast::Module>)
+        .visit(|td: &ast::TypeAliasDef| decl_with_type_ref(td, td.type_ref()))
+        .visit(decl_with_ascription::<ast::NamedFieldDef>)
+        .visit(decl_with_ascription::<ast::ConstDef>)
+        .visit(decl_with_ascription::<ast::StaticDef>)
+        .visit(|im: &ast::ImplBlock| {
+            let target_type = im.target_type()?;
+            let target_trait = im.target_trait();
+            let label = match target_trait {
+                None => format!("impl {}", target_type.syntax().text()),
+                Some(t) => {
+                    format!("impl {} for {}", t.syntax().text(), target_type.syntax().text(),)
+                }
+            };
+
+            let node = StructureNode {
+                parent: None,
+                label,
+                navigation_range: target_type.syntax().range(),
+                node_range: im.syntax().range(),
+                kind: im.syntax().kind(),
+                detail: None,
+                deprecated: false,
+            };
+            Some(node)
+        })
+        .accept(node)?
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use insta::assert_debug_snapshot_matches;
+
+    #[test]
+    fn test_file_structure() {
+        let file = SourceFile::parse(
+            r#"
+struct Foo {
+    x: i32
+}
+
+mod m {
+    fn bar1() {}
+    fn bar2<T>(t: T) -> T {}
+    fn bar3<A,
+        B>(a: A,
+        b: B) -> Vec<
+        u32
+    > {}
+}
+
+enum E { X, Y(i32) }
+type T = ();
+static S: i32 = 92;
+const C: i32 = 92;
+
+impl E {}
+
+impl fmt::Debug for E {}
+
+#[deprecated]
+fn obsolete() {}
+
+#[deprecated(note = "for awhile")]
+fn very_obsolete() {}
+"#,
+        );
+        let structure = file_structure(&file);
+        assert_debug_snapshot_matches!("file_structure", structure);
+    }
+}