1 files changed, 215 insertions, 0 deletions

diff --git a/crates/ra_ide/src/display/function_signature.rs b/crates/ra_ide/src/display/function_signature.rs
new file mode 100644
index 000000000..d96de4e4c
--- /dev/null
+++ b/crates/ra_ide/src/display/function_signature.rs
@@ -0,0 +1,215 @@
+//! FIXME: write short doc here
+
+use std::fmt::{self, Display};
+
+use hir::{Docs, Documentation, HasSource, HirDisplay};
+use join_to_string::join;
+use ra_syntax::ast::{self, AstNode, NameOwner, VisibilityOwner};
+use std::convert::From;
+
+use crate::{
+    db,
+    display::{generic_parameters, where_predicates},
+};
+
+#[derive(Debug)]
+pub enum CallableKind {
+    Function,
+    StructConstructor,
+    VariantConstructor,
+    Macro,
+}
+
+/// Contains information about a function signature
+#[derive(Debug)]
+pub struct FunctionSignature {
+    pub kind: CallableKind,
+    /// 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).value;
+        FunctionSignature::from(&ast_node).with_doc_opt(doc)
+    }
+
+    pub(crate) fn from_struct(db: &db::RootDatabase, st: hir::Struct) -> Option<Self> {
+        let node: ast::StructDef = st.source(db).value;
+        match node.kind() {
+            ast::StructKind::Record(_) => return None,
+            _ => (),
+        };
+
+        let params = st
+            .fields(db)
+            .into_iter()
+            .map(|field: hir::StructField| {
+                let ty = field.ty(db);
+                format!("{}", ty.display(db))
+            })
+            .collect();
+
+        Some(
+            FunctionSignature {
+                kind: CallableKind::StructConstructor,
+                visibility: node.visibility().map(|n| n.syntax().text().to_string()),
+                name: node.name().map(|n| n.text().to_string()),
+                ret_type: node.name().map(|n| n.text().to_string()),
+                parameters: params,
+                generic_parameters: generic_parameters(&node),
+                where_predicates: where_predicates(&node),
+                doc: None,
+            }
+            .with_doc_opt(st.docs(db)),
+        )
+    }
+
+    pub(crate) fn from_enum_variant(
+        db: &db::RootDatabase,
+        variant: hir::EnumVariant,
+    ) -> Option<Self> {
+        let node: ast::EnumVariant = variant.source(db).value;
+        match node.kind() {
+            ast::StructKind::Record(_) | ast::StructKind::Unit => return None,
+            _ => (),
+        };
+
+        let parent_name = match variant.parent_enum(db).name(db) {
+            Some(name) => name.to_string(),
+            None => "missing".into(),
+        };
+
+        let name = format!("{}::{}", parent_name, variant.name(db).unwrap());
+
+        let params = variant
+            .fields(db)
+            .into_iter()
+            .map(|field: hir::StructField| {
+                let name = field.name(db);
+                let ty = field.ty(db);
+                format!("{}: {}", name, ty.display(db))
+            })
+            .collect();
+
+        Some(
+            FunctionSignature {
+                kind: CallableKind::VariantConstructor,
+                visibility: None,
+                name: Some(name),
+                ret_type: None,
+                parameters: params,
+                generic_parameters: vec![],
+                where_predicates: vec![],
+                doc: None,
+            }
+            .with_doc_opt(variant.docs(db)),
+        )
+    }
+
+    pub(crate) fn from_macro(db: &db::RootDatabase, macro_def: hir::MacroDef) -> Option<Self> {
+        let node: ast::MacroCall = macro_def.source(db).value;
+
+        let params = vec![];
+
+        Some(
+            FunctionSignature {
+                kind: CallableKind::Macro,
+                visibility: None,
+                name: node.name().map(|n| n.text().to_string()),
+                ret_type: None,
+                parameters: params,
+                generic_parameters: vec![],
+                where_predicates: vec![],
+                doc: None,
+            }
+            .with_doc_opt(macro_def.docs(db)),
+        )
+    }
+}
+
+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 {
+            kind: CallableKind::Function,
+            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 {
+            match self.kind {
+                CallableKind::Function => write!(f, "fn {}", name)?,
+                CallableKind::StructConstructor => write!(f, "struct {}", name)?,
+                CallableKind::VariantConstructor => write!(f, "{}", name)?,
+                CallableKind::Macro => write!(f, "{}!", 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(())
+    }
+}