5 files changed, 124 insertions, 53 deletions

diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index c4691d34c..d5a3d9034 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -812,13 +812,11 @@ impl Function {
     /// Get this function's return type
     pub fn ret_type(self, db: &dyn HirDatabase) -> Type {
         let resolver = self.id.resolver(db.upcast());
+        let krate = self.id.lookup(db.upcast()).container.module(db.upcast()).krate();
         let ret_type = &db.function_data(self.id).ret_type;
         let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
-        let environment = TraitEnvironment::lower(db, &resolver);
-        Type {
-            krate: self.id.lookup(db.upcast()).container.module(db.upcast()).krate(),
-            ty: InEnvironment { value: Ty::from_hir_ext(&ctx, ret_type).0, environment },
-        }
+        let ty = Ty::from_hir_ext(&ctx, ret_type).0;
+        Type::new_with_resolver_inner(db, krate, &resolver, ty)
     }
 
     pub fn self_param(self, db: &dyn HirDatabase) -> Option<SelfParam> {
@@ -830,6 +828,7 @@ impl Function {
 
     pub fn assoc_fn_params(self, db: &dyn HirDatabase) -> Vec<Param> {
         let resolver = self.id.resolver(db.upcast());
+        let krate = self.id.lookup(db.upcast()).container.module(db.upcast()).krate();
         let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
         let environment = TraitEnvironment::lower(db, &resolver);
         db.function_data(self.id)
@@ -837,7 +836,7 @@ impl Function {
             .iter()
             .map(|type_ref| {
                 let ty = Type {
-                    krate: self.id.lookup(db.upcast()).container.module(db.upcast()).krate(),
+                    krate,
                     ty: InEnvironment {
                         value: Ty::from_hir_ext(&ctx, type_ref).0,
                         environment: environment.clone(),
@@ -1403,12 +1402,9 @@ impl TypeParam {
 
     pub fn ty(self, db: &dyn HirDatabase) -> Type {
         let resolver = self.id.parent.resolver(db.upcast());
-        let environment = TraitEnvironment::lower(db, &resolver);
+        let krate = self.id.parent.module(db.upcast()).krate();
         let ty = Ty::Placeholder(self.id);
-        Type {
-            krate: self.id.parent.module(db.upcast()).krate(),
-            ty: InEnvironment { value: ty, environment },
-        }
+        Type::new_with_resolver_inner(db, krate, &resolver, ty)
     }
 
     pub fn trait_bounds(self, db: &dyn HirDatabase) -> Vec<Trait> {
@@ -1427,14 +1423,11 @@ impl TypeParam {
         let params = db.generic_defaults(self.id.parent);
         let local_idx = hir_ty::param_idx(db, self.id)?;
         let resolver = self.id.parent.resolver(db.upcast());
-        let environment = TraitEnvironment::lower(db, &resolver);
+        let krate = self.id.parent.module(db.upcast()).krate();
         let ty = params.get(local_idx)?.clone();
         let subst = Substs::type_params(db, self.id.parent);
         let ty = ty.subst(&subst.prefix(local_idx));
-        Some(Type {
-            krate: self.id.parent.module(db.upcast()).krate(),
-            ty: InEnvironment { value: ty, environment },
-        })
+        Some(Type::new_with_resolver_inner(db, krate, &resolver, ty))
     }
 }
 
@@ -1523,13 +1516,10 @@ impl Impl {
     pub fn target_ty(self, db: &dyn HirDatabase) -> Type {
         let impl_data = db.impl_data(self.id);
         let resolver = self.id.resolver(db.upcast());
+        let krate = self.id.lookup(db.upcast()).container.module(db.upcast()).krate();
         let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
-        let environment = TraitEnvironment::lower(db, &resolver);
         let ty = Ty::from_hir(&ctx, &impl_data.target_type);
-        Type {
-            krate: self.id.lookup(db.upcast()).container.module(db.upcast()).krate(),
-            ty: InEnvironment { value: ty, environment },
-        }
+        Type::new_with_resolver_inner(db, krate, &resolver, ty)
     }
 
     pub fn items(self, db: &dyn HirDatabase) -> Vec<AssocItem> {
@@ -1725,13 +1715,11 @@ impl Type {
         };
 
         match db.trait_solve(self.krate, goal)? {
-            Solution::Unique(SolutionVariables(subst)) => subst.value.first().cloned(),
+            Solution::Unique(SolutionVariables(subst)) => {
+                subst.value.first().map(|ty| self.derived(ty.clone()))
+            }
             Solution::Ambig(_) => None,
         }
-        .map(|ty| Type {
-            krate: self.krate,
-            ty: InEnvironment { value: ty, environment: Arc::clone(&self.ty.environment) },
-        })
     }
 
     pub fn is_copy(&self, db: &dyn HirDatabase) -> bool {
diff --git a/crates/ide_assists/src/handlers/generate_function.rs b/crates/ide_assists/src/handlers/generate_function.rs
index 3870b7e75..6f95b1a07 100644
--- a/crates/ide_assists/src/handlers/generate_function.rs
+++ b/crates/ide_assists/src/handlers/generate_function.rs
@@ -83,17 +83,18 @@ struct FunctionTemplate {
     leading_ws: String,
     fn_def: ast::Fn,
     ret_type: ast::RetType,
+    should_render_snippet: bool,
     trailing_ws: String,
     file: FileId,
 }
 
 impl FunctionTemplate {
     fn to_string(&self, cap: Option<SnippetCap>) -> String {
-        let f = match cap {
-            Some(cap) => {
+        let f = match (cap, self.should_render_snippet) {
+            (Some(cap), true) => {
                 render_snippet(cap, self.fn_def.syntax(), Cursor::Replace(self.ret_type.syntax()))
             }
-            None => self.fn_def.to_string(),
+            _ => self.fn_def.to_string(),
         };
         format!("{}{}{}", self.leading_ws, f, self.trailing_ws)
     }
@@ -104,6 +105,8 @@ struct FunctionBuilder {
     fn_name: ast::Name,
     type_params: Option<ast::GenericParamList>,
     params: ast::ParamList,
+    ret_type: ast::RetType,
+    should_render_snippet: bool,
     file: FileId,
     needs_pub: bool,
 }
@@ -132,7 +135,43 @@ impl FunctionBuilder {
         let fn_name = fn_name(&path)?;
         let (type_params, params) = fn_args(ctx, target_module, &call)?;
 
-        Some(Self { target, fn_name, type_params, params, file, needs_pub })
+        // should_render_snippet intends to express a rough level of confidence about
+        // the correctness of the return type.
+        //
+        // If we are able to infer some return type, and that return type is not unit, we
+        // don't want to render the snippet. The assumption here is in this situation the
+        // return type is just as likely to be correct as any other part of the generated
+        // function.
+        //
+        // In the case where the return type is inferred as unit it is likely that the
+        // user does in fact intend for this generated function to return some non unit
+        // type, but that the current state of their code doesn't allow that return type
+        // to be accurately inferred.
+        let (ret_ty, should_render_snippet) = {
+            match ctx.sema.type_of_expr(&ast::Expr::CallExpr(call.clone())) {
+                Some(ty) if ty.is_unknown() || ty.is_unit() => (make::ty_unit(), true),
+                Some(ty) => {
+                    let rendered = ty.display_source_code(ctx.db(), target_module.into());
+                    match rendered {
+                        Ok(rendered) => (make::ty(&rendered), false),
+                        Err(_) => (make::ty_unit(), true),
+                    }
+                }
+                None => (make::ty_unit(), true),
+            }
+        };
+        let ret_type = make::ret_type(ret_ty);
+
+        Some(Self {
+            target,
+            fn_name,
+            type_params,
+            params,
+            ret_type,
+            should_render_snippet,
+            file,
+            needs_pub,
+        })
     }
 
     fn render(self) -> FunctionTemplate {
@@ -145,7 +184,7 @@ impl FunctionBuilder {
             self.type_params,
             self.params,
             fn_body,
-            Some(make::ret_type(make::ty_unit())),
+            Some(self.ret_type),
         );
         let leading_ws;
         let trailing_ws;
@@ -171,6 +210,7 @@ impl FunctionBuilder {
             insert_offset,
             leading_ws,
             ret_type: fn_def.ret_type().unwrap(),
+            should_render_snippet: self.should_render_snippet,
             fn_def,
             trailing_ws,
             file: self.file,
@@ -546,7 +586,7 @@ impl Baz {
     }
 }
 
-fn bar(baz: Baz) ${0:-> ()} {
+fn bar(baz: Baz) -> Baz {
     todo!()
 }
 ",
@@ -1060,6 +1100,27 @@ pub(crate) fn bar() ${0:-> ()} {
     }
 
     #[test]
+    fn add_function_with_return_type() {
+        check_assist(
+            generate_function,
+            r"
+fn main() {
+    let x: u32 = foo$0();
+}
+",
+            r"
+fn main() {
+    let x: u32 = foo();
+}
+
+fn foo() -> u32 {
+    todo!()
+}
+",
+        )
+    }
+
+    #[test]
     fn add_function_not_applicable_if_function_already_exists() {
         check_assist_not_applicable(
             generate_function,
diff --git a/crates/ide_completion/src/completions/postfix.rs b/crates/ide_completion/src/completions/postfix.rs
index 9c34ed0b6..d45ad7944 100644
--- a/crates/ide_completion/src/completions/postfix.rs
+++ b/crates/ide_completion/src/completions/postfix.rs
@@ -187,6 +187,16 @@ pub(crate) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
         ctx,
         cap,
         &dot_receiver,
+        "err",
+        "Err(expr)",
+        &format!("Err({})", receiver_text),
+    )
+    .add_to(acc);
+
+    postfix_snippet(
+        ctx,
+        cap,
+        &dot_receiver,
         "some",
         "Some(expr)",
         &format!("Some({})", receiver_text),
@@ -325,6 +335,7 @@ fn main() {
                 sn match match expr {}
                 sn box   Box::new(expr)
                 sn ok    Ok(expr)
+                sn err   Err(expr)
                 sn some  Some(expr)
                 sn dbg   dbg!(expr)
                 sn dbgr  dbg!(&expr)
@@ -357,6 +368,7 @@ fn main() {
                 sn match match expr {}
                 sn box   Box::new(expr)
                 sn ok    Ok(expr)
+                sn err   Err(expr)
                 sn some  Some(expr)
                 sn dbg   dbg!(expr)
                 sn dbgr  dbg!(&expr)
@@ -380,6 +392,7 @@ fn main() {
                 sn match match expr {}
                 sn box   Box::new(expr)
                 sn ok    Ok(expr)
+                sn err   Err(expr)
                 sn some  Some(expr)
                 sn dbg   dbg!(expr)
                 sn dbgr  dbg!(&expr)
@@ -408,6 +421,7 @@ fn main() {
                 sn match match expr {}
                 sn box   Box::new(expr)
                 sn ok    Ok(expr)
+                sn err   Err(expr)
                 sn some  Some(expr)
                 sn dbg   dbg!(expr)
                 sn dbgr  dbg!(&expr)
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 078c83f75..25df13554 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -16,7 +16,6 @@ use ide_db::helpers::{
     insert_use::{InsertUseConfig, MergeBehavior},
     SnippetCap,
 };
-use itertools::Itertools;
 use lsp_types::{ClientCapabilities, MarkupKind};
 use project_model::{CargoConfig, ProjectJson, ProjectJsonData, ProjectManifest, RustcSource};
 use rustc_hash::FxHashSet;
@@ -98,13 +97,15 @@ config_data! {
         diagnostics_enableExperimental: bool    = "true",
         /// List of rust-analyzer diagnostics to disable.
         diagnostics_disabled: FxHashSet<String> = "[]",
-        /// List of warnings that should be displayed with info severity.\n\nThe
-        /// warnings will be indicated by a blue squiggly underline in code and
-        /// a blue icon in the `Problems Panel`.
+        /// List of warnings that should be displayed with info severity.
+        ///
+        /// The warnings will be indicated by a blue squiggly underline in code
+        /// and a blue icon in the `Problems Panel`.
         diagnostics_warningsAsHint: Vec<String> = "[]",
-        /// List of warnings that should be displayed with hint severity.\n\nThe
-        /// warnings will be indicated by faded text or three dots in code and
-        /// will not show up in the `Problems Panel`.
+        /// List of warnings that should be displayed with hint severity.
+        ///
+        /// The warnings will be indicated by faded text or three dots in code
+        /// and will not show up in the `Problems Panel`.
         diagnostics_warningsAsInfo: Vec<String> = "[]",
 
         /// Controls file watching implementation.
@@ -158,7 +159,9 @@ config_data! {
         lens_references: bool = "false",
 
         /// Disable project auto-discovery in favor of explicitly specified set
-        /// of projects.\n\nElements must be paths pointing to `Cargo.toml`,
+        /// of projects.
+        ///
+        /// Elements must be paths pointing to `Cargo.toml`,
         /// `rust-project.json`, or JSON objects in `rust-project.json` format.
         linkedProjects: Vec<ManifestOrProjectJson> = "[]",
 
@@ -177,13 +180,17 @@ config_data! {
         /// Command to be executed instead of 'cargo' for runnables.
         runnables_overrideCargo: Option<String> = "null",
         /// Additional arguments to be passed to cargo for runnables such as
-        /// tests or binaries.\nFor example, it may be `--release`.
+        /// tests or binaries. For example, it may be `--release`.
         runnables_cargoExtraArgs: Vec<String>   = "[]",
 
-        /// Path to the rust compiler sources, for usage in rustc_private projects, or "discover"
-        /// to try to automatically find it. Any project which uses rust-analyzer with the rustcPrivate
+        /// Path to the Cargo.toml of the rust compiler workspace, for usage in rustc_private
+        /// projects, or "discover" to try to automatically find it.
+        ///
+        /// Any project which uses rust-analyzer with the rustcPrivate
         /// crates must set `[package.metadata.rust-analyzer] rustc_private=true` to use it.
-        rustcSource : Option<String> = "null",
+        ///
+        /// This option is not reloaded automatically; you must restart rust-analyzer for it to take effect.
+        rustcSource: Option<String> = "null",
 
         /// Additional arguments to `rustfmt`.
         rustfmt_extraArgs: Vec<String>               = "[]",
@@ -761,7 +768,8 @@ fn schema(fields: &[(&'static str, &'static str, &[&str], &str)]) -> serde_json:
 }
 
 fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json::Value {
-    let doc = doc.iter().map(|it| it.trim()).join(" ");
+    let doc = doc_comment_to_string(doc);
+    let doc = doc.trim_end_matches('\n');
     assert!(
         doc.ends_with('.') && doc.starts_with(char::is_uppercase),
         "bad docs for {}: {:?}",
@@ -850,11 +858,16 @@ fn manual(fields: &[(&'static str, &'static str, &[&str], &str)]) -> String {
         .iter()
         .map(|(field, _ty, doc, default)| {
             let name = format!("rust-analyzer.{}", field.replace("_", "."));
-            format!("[[{}]]{} (default: `{}`)::\n{}\n", name, name, default, doc.join(" "))
+            let doc = doc_comment_to_string(*doc);
+            format!("[[{}]]{} (default: `{}`)::\n+\n--\n{}--\n", name, name, default, doc)
         })
         .collect::<String>()
 }
 
+fn doc_comment_to_string(doc: &[&str]) -> String {
+    doc.iter().map(|it| it.strip_prefix(' ').unwrap_or(it)).map(|it| format!("{}\n", it)).collect()
+}
+
 #[cfg(test)]
 mod tests {
     use std::fs;
@@ -897,13 +910,8 @@ mod tests {
     #[test]
     fn generate_config_documentation() {
         let docs_path = project_root().join("docs/user/generated_config.adoc");
-        let current = fs::read_to_string(&docs_path).unwrap();
         let expected = ConfigData::manual();
-
-        if remove_ws(&current) != remove_ws(&expected) {
-            fs::write(&docs_path, expected).unwrap();
-            panic!("updated config manual");
-        }
+        ensure_file_contents(&docs_path, &expected);
     }
 
     fn remove_ws(text: &str) -> String {
diff --git a/crates/syntax/Cargo.toml b/crates/syntax/Cargo.toml
index c39095def..33bde099b 100644
--- a/crates/syntax/Cargo.toml
+++ b/crates/syntax/Cargo.toml
@@ -25,10 +25,10 @@ serde = { version = "1.0.106", features = ["derive"] }
 stdx = { path = "../stdx", version = "0.0.0" }
 text_edit = { path = "../text_edit", version = "0.0.0" }
 parser = { path = "../parser", version = "0.0.0" }
-test_utils = { path = "../test_utils", version = "0.0.0" }
 profile = { path = "../profile", version = "0.0.0" }
 
 [dev-dependencies]
+test_utils = { path = "../test_utils" }
 walkdir = "2.3.1"
 rayon = "1"
 expect-test = "1.1"