17 files changed, 467 insertions, 244 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index c6f3bdb8e..9baebf643 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -1027,8 +1027,16 @@ impl Type {
         ty: Ty,
     ) -> Option<Type> {
         let krate = resolver.krate()?;
+        Some(Type::new_with_resolver_inner(db, krate, resolver, ty))
+    }
+    pub(crate) fn new_with_resolver_inner(
+        db: &dyn HirDatabase,
+        krate: CrateId,
+        resolver: &Resolver,
+        ty: Ty,
+    ) -> Type {
         let environment = TraitEnvironment::lower(db, &resolver);
-        Some(Type { krate, ty: InEnvironment { value: ty, environment } })
+        Type { krate, ty: InEnvironment { value: ty, environment } }
     }
 
     fn new(db: &dyn HirDatabase, krate: CrateId, lexical_env: impl HasResolver, ty: Ty) -> Type {
@@ -1152,27 +1160,6 @@ impl Type {
         res
     }
 
-    pub fn variant_fields(
-        &self,
-        db: &dyn HirDatabase,
-        def: VariantDef,
-    ) -> Vec<(StructField, Type)> {
-        // FIXME: check that ty and def match
-        match &self.ty.value {
-            Ty::Apply(a_ty) => {
-                let field_types = db.field_types(def.into());
-                def.fields(db)
-                    .into_iter()
-                    .map(|it| {
-                        let ty = field_types[it.id].clone().subst(&a_ty.parameters);
-                        (it, self.derived(ty))
-                    })
-                    .collect()
-            }
-            _ => Vec::new(),
-        }
-    }
-
     pub fn autoderef<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Type> + 'a {
         // There should be no inference vars in types passed here
         // FIXME check that?
diff --git a/crates/ra_hir/src/semantics.rs b/crates/ra_hir/src/semantics.rs
index 2ad231d36..2707e422d 100644
--- a/crates/ra_hir/src/semantics.rs
+++ b/crates/ra_hir/src/semantics.rs
@@ -23,7 +23,7 @@ use crate::{
     semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
     source_analyzer::{resolve_hir_path, SourceAnalyzer},
     AssocItem, Function, HirFileId, ImplDef, InFile, Local, MacroDef, Module, ModuleDef, Name,
-    Origin, Path, ScopeDef, StructField, Trait, Type, TypeParam, VariantDef,
+    Origin, Path, ScopeDef, StructField, Trait, Type, TypeParam,
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -187,14 +187,6 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         self.analyze(field.syntax()).resolve_record_field(self.db, field)
     }
 
-    pub fn resolve_record_literal(&self, record_lit: &ast::RecordLit) -> Option<VariantDef> {
-        self.analyze(record_lit.syntax()).resolve_record_literal(self.db, record_lit)
-    }
-
-    pub fn resolve_record_pattern(&self, record_pat: &ast::RecordPat) -> Option<VariantDef> {
-        self.analyze(record_pat.syntax()).resolve_record_pattern(record_pat)
-    }
-
     pub fn resolve_macro_call(&self, macro_call: &ast::MacroCall) -> Option<MacroDef> {
         let sa = self.analyze(macro_call.syntax());
         let macro_call = self.find_file(macro_call.syntax().clone()).with_value(macro_call);
@@ -212,6 +204,24 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
     // FIXME: use this instead?
     // pub fn resolve_name_ref(&self, name_ref: &ast::NameRef) -> Option<???>;
 
+    pub fn record_literal_missing_fields(
+        &self,
+        literal: &ast::RecordLit,
+    ) -> Vec<(StructField, Type)> {
+        self.analyze(literal.syntax())
+            .record_literal_missing_fields(self.db, literal)
+            .unwrap_or_default()
+    }
+
+    pub fn record_pattern_missing_fields(
+        &self,
+        pattern: &ast::RecordPat,
+    ) -> Vec<(StructField, Type)> {
+        self.analyze(pattern.syntax())
+            .record_pattern_missing_fields(self.db, pattern)
+            .unwrap_or_default()
+    }
+
     pub fn to_def<T: ToDef>(&self, src: &T) -> Option<T::Def> {
         let src = self.find_file(src.syntax().clone()).with_value(src).cloned();
         T::to_def(self, src)
diff --git a/crates/ra_hir/src/source_analyzer.rs b/crates/ra_hir/src/source_analyzer.rs
index 815ca158c..45631f8fd 100644
--- a/crates/ra_hir/src/source_analyzer.rs
+++ b/crates/ra_hir/src/source_analyzer.rs
@@ -14,10 +14,13 @@ use hir_def::{
     },
     expr::{ExprId, Pat, PatId},
     resolver::{resolver_for_scope, Resolver, TypeNs, ValueNs},
-    AsMacroCall, DefWithBodyId,
+    AsMacroCall, DefWithBodyId, LocalStructFieldId, StructFieldId, VariantId,
 };
 use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
-use hir_ty::InferenceResult;
+use hir_ty::{
+    expr::{record_literal_missing_fields, record_pattern_missing_fields},
+    InferenceResult, Substs, Ty,
+};
 use ra_syntax::{
     ast::{self, AstNode},
     SyntaxNode, SyntaxNodePtr, TextUnit,
@@ -25,8 +28,10 @@ use ra_syntax::{
 
 use crate::{
     db::HirDatabase, semantics::PathResolution, Adt, Const, EnumVariant, Function, Local, MacroDef,
-    ModPath, ModuleDef, Path, PathKind, Static, Struct, Trait, Type, TypeAlias, TypeParam,
+    ModPath, ModuleDef, Path, PathKind, Static, Struct, StructField, Trait, Type, TypeAlias,
+    TypeParam,
 };
+use ra_db::CrateId;
 
 /// `SourceAnalyzer` is a convenience wrapper which exposes HIR API in terms of
 /// original source files. It should not be used inside the HIR itself.
@@ -164,23 +169,6 @@ impl SourceAnalyzer {
         Some((struct_field.into(), local))
     }
 
-    pub(crate) fn resolve_record_literal(
-        &self,
-        db: &dyn HirDatabase,
-        record_lit: &ast::RecordLit,
-    ) -> Option<crate::VariantDef> {
-        let expr_id = self.expr_id(db, &record_lit.clone().into())?;
-        self.infer.as_ref()?.variant_resolution_for_expr(expr_id).map(|it| it.into())
-    }
-
-    pub(crate) fn resolve_record_pattern(
-        &self,
-        record_pat: &ast::RecordPat,
-    ) -> Option<crate::VariantDef> {
-        let pat_id = self.pat_id(&record_pat.clone().into())?;
-        self.infer.as_ref()?.variant_resolution_for_pat(pat_id).map(|it| it.into())
-    }
-
     pub(crate) fn resolve_macro_call(
         &self,
         db: &dyn HirDatabase,
@@ -231,6 +219,68 @@ impl SourceAnalyzer {
         resolve_hir_path(db, &self.resolver, &hir_path)
     }
 
+    pub(crate) fn record_literal_missing_fields(
+        &self,
+        db: &dyn HirDatabase,
+        literal: &ast::RecordLit,
+    ) -> Option<Vec<(StructField, Type)>> {
+        let krate = self.resolver.krate()?;
+        let body = self.body.as_ref()?;
+        let infer = self.infer.as_ref()?;
+
+        let expr_id = self.expr_id(db, &literal.clone().into())?;
+        let substs = match &infer.type_of_expr[expr_id] {
+            Ty::Apply(a_ty) => &a_ty.parameters,
+            _ => return None,
+        };
+
+        let (variant, missing_fields, _exhaustive) =
+            record_literal_missing_fields(db, infer, expr_id, &body[expr_id])?;
+        let res = self.missing_fields(db, krate, substs, variant, missing_fields);
+        Some(res)
+    }
+
+    pub(crate) fn record_pattern_missing_fields(
+        &self,
+        db: &dyn HirDatabase,
+        pattern: &ast::RecordPat,
+    ) -> Option<Vec<(StructField, Type)>> {
+        let krate = self.resolver.krate()?;
+        let body = self.body.as_ref()?;
+        let infer = self.infer.as_ref()?;
+
+        let pat_id = self.pat_id(&pattern.clone().into())?;
+        let substs = match &infer.type_of_pat[pat_id] {
+            Ty::Apply(a_ty) => &a_ty.parameters,
+            _ => return None,
+        };
+
+        let (variant, missing_fields) =
+            record_pattern_missing_fields(db, infer, pat_id, &body[pat_id])?;
+        let res = self.missing_fields(db, krate, substs, variant, missing_fields);
+        Some(res)
+    }
+
+    fn missing_fields(
+        &self,
+        db: &dyn HirDatabase,
+        krate: CrateId,
+        substs: &Substs,
+        variant: VariantId,
+        missing_fields: Vec<LocalStructFieldId>,
+    ) -> Vec<(StructField, Type)> {
+        let field_types = db.field_types(variant);
+
+        missing_fields
+            .into_iter()
+            .map(|local_id| {
+                let field = StructFieldId { parent: variant, local_id };
+                let ty = field_types[local_id].clone().subst(substs);
+                (field.into(), Type::new_with_resolver_inner(db, krate, &self.resolver, ty))
+            })
+            .collect()
+    }
+
     pub(crate) fn expand(
         &self,
         db: &dyn HirDatabase,
diff --git a/crates/ra_hir_ty/src/_match.rs b/crates/ra_hir_ty/src/_match.rs
index f29a25505..9e9a9d047 100644
--- a/crates/ra_hir_ty/src/_match.rs
+++ b/crates/ra_hir_ty/src/_match.rs
@@ -235,7 +235,10 @@ impl From<PatId> for PatIdOrWild {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq)]
-pub struct MatchCheckNotImplemented;
+pub enum MatchCheckErr {
+    NotImplemented,
+    MalformedMatchArm,
+}
 
 /// The return type of `is_useful` is either an indication of usefulness
 /// of the match arm, or an error in the case the match statement
@@ -244,7 +247,7 @@ pub struct MatchCheckNotImplemented;
 ///
 /// The `std::result::Result` type is used here rather than a custom enum
 /// to allow the use of `?`.
-pub type MatchCheckResult<T> = Result<T, MatchCheckNotImplemented>;
+pub type MatchCheckResult<T> = Result<T, MatchCheckErr>;
 
 #[derive(Debug)]
 /// A row in a Matrix.
@@ -335,12 +338,12 @@ impl PatStack {
                     Expr::Literal(Literal::Bool(_)) => None,
                     // perhaps this is actually unreachable given we have
                     // already checked that these match arms have the appropriate type?
-                    _ => return Err(MatchCheckNotImplemented),
+                    _ => return Err(MatchCheckErr::NotImplemented),
                 }
             }
             (Pat::Wild, constructor) => Some(self.expand_wildcard(cx, constructor)?),
             (Pat::Path(_), Constructor::Enum(constructor)) => {
-                // enums with no associated data become `Pat::Path`
+                // unit enum variants become `Pat::Path`
                 let pat_id = self.head().as_id().expect("we know this isn't a wild");
                 if !enum_variant_matches(cx, pat_id, *constructor) {
                     None
@@ -348,16 +351,23 @@ impl PatStack {
                     Some(self.to_tail())
                 }
             }
-            (Pat::TupleStruct { args: ref pat_ids, .. }, Constructor::Enum(constructor)) => {
+            (Pat::TupleStruct { args: ref pat_ids, .. }, Constructor::Enum(enum_constructor)) => {
                 let pat_id = self.head().as_id().expect("we know this isn't a wild");
-                if !enum_variant_matches(cx, pat_id, *constructor) {
+                if !enum_variant_matches(cx, pat_id, *enum_constructor) {
                     None
                 } else {
+                    // If the enum variant matches, then we need to confirm
+                    // that the number of patterns aligns with the expected
+                    // number of patterns for that enum variant.
+                    if pat_ids.len() != constructor.arity(cx)? {
+                        return Err(MatchCheckErr::MalformedMatchArm);
+                    }
+
                     Some(self.replace_head_with(pat_ids))
                 }
             }
-            (Pat::Or(_), _) => return Err(MatchCheckNotImplemented),
-            (_, _) => return Err(MatchCheckNotImplemented),
+            (Pat::Or(_), _) => return Err(MatchCheckErr::NotImplemented),
+            (_, _) => return Err(MatchCheckErr::NotImplemented),
         };
 
         Ok(result)
@@ -514,7 +524,7 @@ pub(crate) fn is_useful(
         return if any_useful {
             Ok(Usefulness::Useful)
         } else if found_unimplemented {
-            Err(MatchCheckNotImplemented)
+            Err(MatchCheckErr::NotImplemented)
         } else {
             Ok(Usefulness::NotUseful)
         };
@@ -567,7 +577,7 @@ pub(crate) fn is_useful(
                 }
 
                 if found_unimplemented {
-                    Err(MatchCheckNotImplemented)
+                    Err(MatchCheckErr::NotImplemented)
                 } else {
                     Ok(Usefulness::NotUseful)
                 }
@@ -604,7 +614,7 @@ impl Constructor {
                 match cx.db.enum_data(e.parent).variants[e.local_id].variant_data.as_ref() {
                     VariantData::Tuple(struct_field_data) => struct_field_data.len(),
                     VariantData::Unit => 0,
-                    _ => return Err(MatchCheckNotImplemented),
+                    _ => return Err(MatchCheckErr::NotImplemented),
                 }
             }
         };
@@ -637,20 +647,20 @@ fn pat_constructor(cx: &MatchCheckCtx, pat: PatIdOrWild) -> MatchCheckResult<Opt
         Pat::Tuple(pats) => Some(Constructor::Tuple { arity: pats.len() }),
         Pat::Lit(lit_expr) => match cx.body.exprs[lit_expr] {
             Expr::Literal(Literal::Bool(val)) => Some(Constructor::Bool(val)),
-            _ => return Err(MatchCheckNotImplemented),
+            _ => return Err(MatchCheckErr::NotImplemented),
         },
         Pat::TupleStruct { .. } | Pat::Path(_) => {
             let pat_id = pat.as_id().expect("we already know this pattern is not a wild");
             let variant_id =
-                cx.infer.variant_resolution_for_pat(pat_id).ok_or(MatchCheckNotImplemented)?;
+                cx.infer.variant_resolution_for_pat(pat_id).ok_or(MatchCheckErr::NotImplemented)?;
             match variant_id {
                 VariantId::EnumVariantId(enum_variant_id) => {
                     Some(Constructor::Enum(enum_variant_id))
                 }
-                _ => return Err(MatchCheckNotImplemented),
+                _ => return Err(MatchCheckErr::NotImplemented),
             }
         }
-        _ => return Err(MatchCheckNotImplemented),
+        _ => return Err(MatchCheckErr::NotImplemented),
     };
 
     Ok(res)
@@ -1325,6 +1335,40 @@ mod tests {
     }
 
     #[test]
+    fn malformed_match_arm_tuple_missing_pattern() {
+        let content = r"
+            fn test_fn() {
+                match (0) {
+                    () => (),
+                }
+            }
+        ";
+
+        // Match arms with the incorrect type are filtered out.
+        check_diagnostic(content);
+    }
+
+    #[test]
+    fn malformed_match_arm_tuple_enum_missing_pattern() {
+        let content = r"
+            enum Either {
+                A,
+                B(u32),
+            }
+            fn test_fn() {
+                match Either::A {
+                    Either::A => (),
+                    Either::B() => (),
+                }
+            }
+        ";
+
+        // We are testing to be sure we don't panic here when the match
+        // arm `Either::B` is missing its pattern.
+        check_no_diagnostic(content);
+    }
+
+    #[test]
     fn enum_not_in_scope() {
         let content = r"
             fn test_fn() {
diff --git a/crates/ra_hir_ty/src/expr.rs b/crates/ra_hir_ty/src/expr.rs
index fb779cbef..e45e9ea14 100644
--- a/crates/ra_hir_ty/src/expr.rs
+++ b/crates/ra_hir_ty/src/expr.rs
@@ -2,12 +2,8 @@
 
 use std::sync::Arc;
 
-use hir_def::{
-    path::{path, Path},
-    resolver::HasResolver,
-    AdtId, FunctionId,
-};
-use hir_expand::{diagnostics::DiagnosticSink, name::Name};
+use hir_def::{path::path, resolver::HasResolver, AdtId, FunctionId};
+use hir_expand::diagnostics::DiagnosticSink;
 use ra_syntax::{ast, AstPtr};
 use rustc_hash::FxHashSet;
 
@@ -28,7 +24,7 @@ pub use hir_def::{
         ArithOp, Array, BinaryOp, BindingAnnotation, CmpOp, Expr, ExprId, Literal, LogicOp,
         MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField, Statement, UnaryOp,
     },
-    VariantId,
+    LocalStructFieldId, VariantId,
 };
 
 pub struct ExprValidator<'a, 'b: 'a> {
@@ -49,14 +45,37 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
     pub fn validate_body(&mut self, db: &dyn HirDatabase) {
         let body = db.body(self.func.into());
 
-        for e in body.exprs.iter() {
-            if let (id, Expr::RecordLit { path, fields, spread }) = e {
-                self.validate_record_literal(id, path, fields, *spread, db);
-            } else if let (id, Expr::Match { expr, arms }) = e {
+        for (id, expr) in body.exprs.iter() {
+            if let Some((variant_def, missed_fields, true)) =
+                record_literal_missing_fields(db, &self.infer, id, expr)
+            {
+                // XXX: only look at source_map if we do have missing fields
+                let (_, source_map) = db.body_with_source_map(self.func.into());
+
+                if let Ok(source_ptr) = source_map.expr_syntax(id) {
+                    if let Some(expr) = source_ptr.value.left() {
+                        let root = source_ptr.file_syntax(db.upcast());
+                        if let ast::Expr::RecordLit(record_lit) = expr.to_node(&root) {
+                            if let Some(field_list) = record_lit.record_field_list() {
+                                let variant_data = variant_data(db.upcast(), variant_def);
+                                let missed_fields = missed_fields
+                                    .into_iter()
+                                    .map(|idx| variant_data.fields()[idx].name.clone())
+                                    .collect();
+                                self.sink.push(MissingFields {
+                                    file: source_ptr.file_id,
+                                    field_list: AstPtr::new(&field_list),
+                                    missed_fields,
+                                })
+                            }
+                        }
+                    }
+                }
+            }
+            if let Expr::Match { expr, arms } = expr {
                 self.validate_match(id, *expr, arms, db, self.infer.clone());
             }
         }
-
         let body_expr = &body[body.body_expr];
         if let Expr::Block { tail: Some(t), .. } = body_expr {
             self.validate_results_in_tail_expr(body.body_expr, *t, db);
@@ -145,61 +164,6 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         }
     }
 
-    fn validate_record_literal(
-        &mut self,
-        id: ExprId,
-        _path: &Option<Path>,
-        fields: &[RecordLitField],
-        spread: Option<ExprId>,
-        db: &dyn HirDatabase,
-    ) {
-        if spread.is_some() {
-            return;
-        };
-        let variant_def: VariantId = match self.infer.variant_resolution_for_expr(id) {
-            Some(VariantId::UnionId(_)) | None => return,
-            Some(it) => it,
-        };
-        if let VariantId::UnionId(_) = variant_def {
-            return;
-        }
-
-        let variant_data = variant_data(db.upcast(), variant_def);
-
-        let lit_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect();
-        let missed_fields: Vec<Name> = variant_data
-            .fields()
-            .iter()
-            .filter_map(|(_f, d)| {
-                let name = d.name.clone();
-                if lit_fields.contains(&name) {
-                    None
-                } else {
-                    Some(name)
-                }
-            })
-            .collect();
-        if missed_fields.is_empty() {
-            return;
-        }
-        let (_, source_map) = db.body_with_source_map(self.func.into());
-
-        if let Ok(source_ptr) = source_map.expr_syntax(id) {
-            if let Some(expr) = source_ptr.value.left() {
-                let root = source_ptr.file_syntax(db.upcast());
-                if let ast::Expr::RecordLit(record_lit) = expr.to_node(&root) {
-                    if let Some(field_list) = record_lit.record_field_list() {
-                        self.sink.push(MissingFields {
-                            file: source_ptr.file_id,
-                            field_list: AstPtr::new(&field_list),
-                            missed_fields,
-                        })
-                    }
-                }
-            }
-        }
-    }
-
     fn validate_results_in_tail_expr(&mut self, body_id: ExprId, id: ExprId, db: &dyn HirDatabase) {
         // the mismatch will be on the whole block currently
         let mismatch = match self.infer.type_mismatch_for_expr(body_id) {
@@ -232,3 +196,63 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         }
     }
 }
+
+pub fn record_literal_missing_fields(
+    db: &dyn HirDatabase,
+    infer: &InferenceResult,
+    id: ExprId,
+    expr: &Expr,
+) -> Option<(VariantId, Vec<LocalStructFieldId>, /*exhaustive*/ bool)> {
+    let (fields, exhausitve) = match expr {
+        Expr::RecordLit { path: _, fields, spread } => (fields, spread.is_none()),
+        _ => return None,
+    };
+
+    let variant_def = infer.variant_resolution_for_expr(id)?;
+    if let VariantId::UnionId(_) = variant_def {
+        return None;
+    }
+
+    let variant_data = variant_data(db.upcast(), variant_def);
+
+    let specified_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect();
+    let missed_fields: Vec<LocalStructFieldId> = variant_data
+        .fields()
+        .iter()
+        .filter_map(|(f, d)| if specified_fields.contains(&d.name) { None } else { Some(f) })
+        .collect();
+    if missed_fields.is_empty() {
+        return None;
+    }
+    Some((variant_def, missed_fields, exhausitve))
+}
+
+pub fn record_pattern_missing_fields(
+    db: &dyn HirDatabase,
+    infer: &InferenceResult,
+    id: PatId,
+    pat: &Pat,
+) -> Option<(VariantId, Vec<LocalStructFieldId>)> {
+    let fields = match pat {
+        Pat::Record { path: _, args } => args,
+        _ => return None,
+    };
+
+    let variant_def = infer.variant_resolution_for_pat(id)?;
+    if let VariantId::UnionId(_) = variant_def {
+        return None;
+    }
+
+    let variant_data = variant_data(db.upcast(), variant_def);
+
+    let specified_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect();
+    let missed_fields: Vec<LocalStructFieldId> = variant_data
+        .fields()
+        .iter()
+        .filter_map(|(f, d)| if specified_fields.contains(&d.name) { None } else { Some(f) })
+        .collect();
+    if missed_fields.is_empty() {
+        return None;
+    }
+    Some((variant_def, missed_fields))
+}
diff --git a/crates/ra_hir_ty/src/tests.rs b/crates/ra_hir_ty/src/tests.rs
index 060814e53..608408d88 100644
--- a/crates/ra_hir_ty/src/tests.rs
+++ b/crates/ra_hir_ty/src/tests.rs
@@ -336,7 +336,7 @@ fn no_such_field_with_feature_flag_diagnostics() {
             pub(crate) fn new(my_val: usize, bar: bool) -> Self {
                 Self { my_val, bar }
             }
-        
+
             #[cfg(not(feature = "foo"))]
             pub(crate) fn new(my_val: usize, _bar: bool) -> Self {
                 Self { my_val }
diff --git a/crates/ra_ide/src/completion/complete_record.rs b/crates/ra_ide/src/completion/complete_record.rs
index 79f5c8c8f..f46bcee5c 100644
--- a/crates/ra_ide/src/completion/complete_record.rs
+++ b/crates/ra_ide/src/completion/complete_record.rs
@@ -1,65 +1,24 @@
 //! Complete fields in record literals and patterns.
-use ra_syntax::{ast, ast::NameOwner, SmolStr};
-
 use crate::completion::{CompletionContext, Completions};
 
 pub(super) fn complete_record(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
-    let (ty, variant, already_present_fields) =
-        match (ctx.record_lit_pat.as_ref(), ctx.record_lit_syntax.as_ref()) {
-            (None, None) => return None,
-            (Some(_), Some(_)) => unreachable!("A record cannot be both a literal and a pattern"),
-            (Some(record_pat), _) => (
-                ctx.sema.type_of_pat(&record_pat.clone().into())?,
-                ctx.sema.resolve_record_pattern(record_pat)?,
-                pattern_ascribed_fields(record_pat),
-            ),
-            (_, Some(record_lit)) => (
-                ctx.sema.type_of_expr(&record_lit.clone().into())?,
-                ctx.sema.resolve_record_literal(record_lit)?,
-                literal_ascribed_fields(record_lit),
-            ),
-        };
+    let missing_fields = match (ctx.record_lit_pat.as_ref(), ctx.record_lit_syntax.as_ref()) {
+        (None, None) => return None,
+        (Some(_), Some(_)) => unreachable!("A record cannot be both a literal and a pattern"),
+        (Some(record_pat), _) => ctx.sema.record_pattern_missing_fields(record_pat),
+        (_, Some(record_lit)) => ctx.sema.record_literal_missing_fields(record_lit),
+    };
 
-    for (field, field_ty) in ty.variant_fields(ctx.db, variant).into_iter().filter(|(field, _)| {
-        // FIXME: already_present_names better be `Vec<hir::Name>`
-        !already_present_fields.contains(&SmolStr::from(field.name(ctx.db).to_string()))
-    }) {
-        acc.add_field(ctx, field, &field_ty);
+    for (field, ty) in missing_fields {
+        acc.add_field(ctx, field, &ty)
     }
-    Some(())
-}
-
-fn literal_ascribed_fields(record_lit: &ast::RecordLit) -> Vec<SmolStr> {
-    record_lit
-        .record_field_list()
-        .map(|field_list| field_list.fields())
-        .map(|fields| {
-            fields
-                .into_iter()
-                .filter_map(|field| field.name_ref())
-                .map(|name_ref| name_ref.text().clone())
-                .collect()
-        })
-        .unwrap_or_default()
-}
 
-fn pattern_ascribed_fields(record_pat: &ast::RecordPat) -> Vec<SmolStr> {
-    record_pat
-        .record_field_pat_list()
-        .map(|pat_list| {
-            pat_list
-                .record_field_pats()
-                .filter_map(|fild_pat| fild_pat.name())
-                .chain(pat_list.bind_pats().filter_map(|bind_pat| bind_pat.name()))
-                .map(|name| name.text().clone())
-                .collect()
-        })
-        .unwrap_or_default()
+    Some(())
 }
 
 #[cfg(test)]
 mod tests {
-    mod record_lit_tests {
+    mod record_pat_tests {
         use insta::assert_debug_snapshot;
 
         use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
@@ -205,7 +164,7 @@ mod tests {
         }
     }
 
-    mod record_pat_tests {
+    mod record_lit_tests {
         use insta::assert_debug_snapshot;
 
         use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
@@ -410,5 +369,38 @@ mod tests {
         ]
         "###);
         }
+
+        #[test]
+        fn completes_functional_update() {
+            let completions = complete(
+                r"
+            struct S {
+                foo1: u32,
+                foo2: u32,
+            }
+
+            fn main() {
+                let foo1 = 1;
+                let s = S {
+                    foo1,
+                    <|>
+                    .. loop {}
+                }
+            }
+            ",
+            );
+            assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "foo2",
+                source_range: [221; 221),
+                delete: [221; 221),
+                insert: "foo2",
+                kind: Field,
+                detail: "u32",
+            },
+        ]
+        "###);
+        }
     }
 }
diff --git a/crates/ra_ide/src/snapshots/highlight_injection.html b/crates/ra_ide/src/snapshots/highlight_injection.html
new file mode 100644
index 000000000..6ec13bd80
--- /dev/null
+++ b/crates/ra_ide/src/snapshots/highlight_injection.html
@@ -0,0 +1,39 @@
+
+<style>
+body                { margin: 0; }
+pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
+
+.lifetime           { color: #DFAF8F; font-style: italic; }
+.comment            { color: #7F9F7F; }
+.struct, .enum      { color: #7CB8BB; }
+.enum_variant       { color: #BDE0F3; }
+.string_literal     { color: #CC9393; }
+.field              { color: #94BFF3; }
+.function           { color: #93E0E3; }
+.parameter          { color: #94BFF3; }
+.text               { color: #DCDCCC; }
+.type               { color: #7CB8BB; }
+.builtin_type       { color: #8CD0D3; }
+.type_param         { color: #DFAF8F; }
+.attribute          { color: #94BFF3; }
+.numeric_literal    { color: #BFEBBF; }
+.macro              { color: #94BFF3; }
+.module             { color: #AFD8AF; }
+.variable           { color: #DCDCCC; }
+.mutable            { text-decoration: underline; }
+
+.keyword            { color: #F0DFAF; font-weight: bold; }
+.keyword.unsafe     { color: #BC8383; font-weight: bold; }
+.control            { font-style: italic; }
+</style>
+<pre><code><span class="keyword">fn</span> <span class="function declaration">fixture</span>(<span class="variable declaration">ra_fixture</span>: &<span class="builtin_type">str</span>) {}
+
+<span class="keyword">fn</span> <span class="function declaration">main</span>() {
+    <span class="function">fixture</span>(<span class="string_literal">r#"</span>
+        <span class="keyword">trait</span> <span class="trait declaration">Foo</span> {
+            <span class="keyword">fn</span> <span class="function declaration">foo</span>() {
+                <span class="macro">println!</span>(<span class="string_literal">"2 + 2 = {}"</span>, <span class="numeric_literal">4</span>);
+            }
+        }<span class="string_literal">"#</span>
+    );
+}</code></pre>
\ No newline at end of file
diff --git a/crates/ra_ide/src/snapshots/highlighting.html b/crates/ra_ide/src/snapshots/highlighting.html
index 495b07f69..214dcbb62 100644
--- a/crates/ra_ide/src/snapshots/highlighting.html
+++ b/crates/ra_ide/src/snapshots/highlighting.html
@@ -26,7 +26,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .keyword.unsafe     { color: #BC8383; font-weight: bold; }
 .control            { font-style: italic; }
 </style>
-<pre><code><span class="attribute">#</span><span class="attribute">[</span><span class="attribute">derive</span><span class="attribute">(</span><span class="attribute">Clone</span><span class="attribute">,</span><span class="attribute"> </span><span class="attribute">Debug</span><span class="attribute">)</span><span class="attribute">]</span>
+<pre><code><span class="attribute">#[derive(Clone, Debug)]</span>
 <span class="keyword">struct</span> <span class="struct declaration">Foo</span> {
     <span class="keyword">pub</span> <span class="field declaration">x</span>: <span class="builtin_type">i32</span>,
     <span class="keyword">pub</span> <span class="field declaration">y</span>: <span class="builtin_type">i32</span>,
@@ -36,11 +36,11 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     <span class="function">foo</span>::&lt;<span class="lifetime">'a</span>, <span class="builtin_type">i32</span>&gt;()
 }
 
-<span class="macro">macro_rules</span><span class="macro">!</span> def_fn {
+<span class="macro">macro_rules!</span> def_fn {
     ($($tt:tt)*) =&gt; {$($tt)*}
 }
 
-<span class="macro">def_fn</span><span class="macro">!</span> {
+<span class="macro">def_fn!</span> {
     <span class="keyword">fn</span> <span class="function declaration">bar</span>() -&gt; <span class="builtin_type">u32</span> {
         <span class="numeric_literal">100</span>
     }
@@ -48,7 +48,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 
 <span class="comment">// comment</span>
 <span class="keyword">fn</span> <span class="function declaration">main</span>() {
-    <span class="macro">println</span><span class="macro">!</span>(<span class="string_literal">"Hello, {}!"</span>, <span class="numeric_literal">92</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello, {}!"</span>, <span class="numeric_literal">92</span>);
 
     <span class="keyword">let</span> <span class="keyword">mut</span> <span class="variable declaration mutable">vec</span> = Vec::new();
     <span class="keyword control">if</span> <span class="keyword">true</span> {
@@ -73,7 +73,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="keyword">impl</span>&lt;<span class="type_param declaration">T</span>&gt; <span class="enum">Option</span>&lt;<span class="type_param">T</span>&gt; {
     <span class="keyword">fn</span> <span class="function declaration">and</span>&lt;<span class="type_param declaration">U</span>&gt;(<span class="keyword">self</span>, <span class="variable declaration">other</span>: <span class="enum">Option</span>&lt;<span class="type_param">U</span>&gt;) -&gt; <span class="enum">Option</span>&lt;(<span class="type_param">T</span>, <span class="type_param">U</span>)&gt; {
         <span class="keyword control">match</span> <span class="variable">other</span> {
-            <span class="enum_variant">None</span> =&gt; <span class="macro">unimplemented</span><span class="macro">!</span>(),
+            <span class="enum_variant">None</span> =&gt; <span class="macro">unimplemented!</span>(),
             <span class="variable declaration">Nope</span> =&gt; <span class="variable">Nope</span>,
         }
     }
diff --git a/crates/ra_ide/src/syntax_highlighting.rs b/crates/ra_ide/src/syntax_highlighting.rs
index d833a816b..83d161f45 100644
--- a/crates/ra_ide/src/syntax_highlighting.rs
+++ b/crates/ra_ide/src/syntax_highlighting.rs
@@ -24,7 +24,7 @@ use crate::{call_info::call_info_for_token, Analysis, FileId};
 pub(crate) use html::highlight_as_html;
 pub use tags::{Highlight, HighlightModifier, HighlightModifiers, HighlightTag};
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct HighlightedRange {
     pub range: TextRange,
     pub highlight: Highlight,
@@ -55,13 +55,55 @@ pub(crate) fn highlight(
     };
 
     let mut bindings_shadow_count: FxHashMap<Name, u32> = FxHashMap::default();
-    let mut res = Vec::new();
+    // We use a stack for the DFS traversal below.
+    // When we leave a node, the we use it to flatten the highlighted ranges.
+    let mut res: Vec<Vec<HighlightedRange>> = vec![Vec::new()];
 
     let mut current_macro_call: Option<ast::MacroCall> = None;
 
     // Walk all nodes, keeping track of whether we are inside a macro or not.
     // If in macro, expand it first and highlight the expanded code.
     for event in root.preorder_with_tokens() {
+        match &event {
+            WalkEvent::Enter(_) => res.push(Vec::new()),
+            WalkEvent::Leave(_) => {
+                /* Flattens the highlighted ranges.
+                 *
+                 * For example `#[cfg(feature = "foo")]` contains the nested ranges:
+                 * 1) parent-range: Attribute [0, 23)
+                 * 2) child-range: String [16, 21)
+                 *
+                 * The following code implements the flattening, for our example this results to:
+                 * `[Attribute [0, 16), String [16, 21), Attribute [21, 23)]`
+                 */
+                let children = res.pop().unwrap();
+                let prev = res.last_mut().unwrap();
+                let needs_flattening = !children.is_empty()
+                    && !prev.is_empty()
+                    && children.first().unwrap().range.is_subrange(&prev.last().unwrap().range);
+                if !needs_flattening {
+                    prev.extend(children);
+                } else {
+                    let mut parent = prev.pop().unwrap();
+                    for ele in children {
+                        assert!(ele.range.is_subrange(&parent.range));
+                        let mut cloned = parent.clone();
+                        parent.range = TextRange::from_to(parent.range.start(), ele.range.start());
+                        cloned.range = TextRange::from_to(ele.range.end(), cloned.range.end());
+                        if !parent.range.is_empty() {
+                            prev.push(parent);
+                        }
+                        prev.push(ele);
+                        parent = cloned;
+                    }
+                    if !parent.range.is_empty() {
+                        prev.push(parent);
+                    }
+                }
+            }
+        };
+        let current = res.last_mut().expect("during DFS traversal, the stack must not be empty");
+
         let event_range = match &event {
             WalkEvent::Enter(it) => it.text_range(),
             WalkEvent::Leave(it) => it.text_range(),
@@ -77,7 +119,7 @@ pub(crate) fn highlight(
             WalkEvent::Enter(Some(mc)) => {
                 current_macro_call = Some(mc.clone());
                 if let Some(range) = macro_call_range(&mc) {
-                    res.push(HighlightedRange {
+                    current.push(HighlightedRange {
                         range,
                         highlight: HighlightTag::Macro.into(),
                         binding_hash: None,
@@ -119,7 +161,7 @@ pub(crate) fn highlight(
 
         if let Some(token) = element.as_token().cloned().and_then(ast::RawString::cast) {
             let expanded = element_to_highlight.as_token().unwrap().clone();
-            if highlight_injection(&mut res, &sema, token, expanded).is_some() {
+            if highlight_injection(current, &sema, token, expanded).is_some() {
                 continue;
             }
         }
@@ -127,10 +169,17 @@ pub(crate) fn highlight(
         if let Some((highlight, binding_hash)) =
             highlight_element(&sema, &mut bindings_shadow_count, element_to_highlight)
         {
-            res.push(HighlightedRange { range, highlight, binding_hash });
+            current.push(HighlightedRange { range, highlight, binding_hash });
         }
     }
 
+    assert_eq!(res.len(), 1, "after DFS traversal, the stack should only contain a single element");
+    let res = res.pop().unwrap();
+    // Check that ranges are sorted and disjoint
+    assert!(res
+        .iter()
+        .zip(res.iter().skip(1))
+        .all(|(left, right)| left.range.end() <= right.range.start()));
     res
 }
 
diff --git a/crates/ra_ide/src/syntax_highlighting/html.rs b/crates/ra_ide/src/syntax_highlighting/html.rs
index e13766c9d..4496529a1 100644
--- a/crates/ra_ide/src/syntax_highlighting/html.rs
+++ b/crates/ra_ide/src/syntax_highlighting/html.rs
@@ -1,9 +1,9 @@
 //! Renders a bit of code as HTML.
 
 use ra_db::SourceDatabase;
-use ra_syntax::AstNode;
+use ra_syntax::{AstNode, TextUnit};
 
-use crate::{FileId, HighlightedRange, RootDatabase};
+use crate::{FileId, RootDatabase};
 
 use super::highlight;
 
@@ -21,51 +21,35 @@ pub(crate) fn highlight_as_html(db: &RootDatabase, file_id: FileId, rainbow: boo
         )
     }
 
-    let mut ranges = highlight(db, file_id, None);
-    ranges.sort_by_key(|it| it.range.start());
-    // quick non-optimal heuristic to intersect token ranges and highlighted ranges
-    let mut frontier = 0;
-    let mut could_intersect: Vec<&HighlightedRange> = Vec::new();
-
+    let ranges = highlight(db, file_id, None);
+    let text = parse.tree().syntax().to_string();
+    let mut prev_pos = TextUnit::from(0);
     let mut buf = String::new();
     buf.push_str(&STYLE);
     buf.push_str("<pre><code>");
-    let tokens = parse.tree().syntax().descendants_with_tokens().filter_map(|it| it.into_token());
-    for token in tokens {
-        could_intersect.retain(|it| token.text_range().start() <= it.range.end());
-        while let Some(r) = ranges.get(frontier) {
-            if r.range.start() <= token.text_range().end() {
-                could_intersect.push(r);
-                frontier += 1;
-            } else {
-                break;
-            }
-        }
-        let text = html_escape(&token.text());
-        let ranges = could_intersect
-            .iter()
-            .filter(|it| token.text_range().is_subrange(&it.range))
-            .collect::<Vec<_>>();
-        if ranges.is_empty() {
+    for range in &ranges {
+        if range.range.start() > prev_pos {
+            let curr = &text[prev_pos.to_usize()..range.range.start().to_usize()];
+            let text = html_escape(curr);
             buf.push_str(&text);
-        } else {
-            let classes = ranges
-                .iter()
-                .map(|it| it.highlight.to_string().replace('.', " "))
-                .collect::<Vec<_>>()
-                .join(" ");
-            let binding_hash = ranges.first().and_then(|x| x.binding_hash);
-            let color = match (rainbow, binding_hash) {
-                (true, Some(hash)) => format!(
-                    " data-binding-hash=\"{}\" style=\"color: {};\"",
-                    hash,
-                    rainbowify(hash)
-                ),
-                _ => "".into(),
-            };
-            buf.push_str(&format!("<span class=\"{}\"{}>{}</span>", classes, color, text));
         }
+        let curr = &text[range.range.start().to_usize()..range.range.end().to_usize()];
+
+        let class = range.highlight.to_string().replace('.', " ");
+        let color = match (rainbow, range.binding_hash) {
+            (true, Some(hash)) => {
+                format!(" data-binding-hash=\"{}\" style=\"color: {};\"", hash, rainbowify(hash))
+            }
+            _ => "".into(),
+        };
+        buf.push_str(&format!("<span class=\"{}\"{}>{}</span>", class, color, html_escape(curr)));
+
+        prev_pos = range.range.end();
     }
+    // Add the remaining (non-highlighted) text
+    let curr = &text[prev_pos.to_usize()..];
+    let text = html_escape(curr);
+    buf.push_str(&text);
     buf.push_str("</code></pre>");
     buf
 }
diff --git a/crates/ra_ide/src/syntax_highlighting/tests.rs b/crates/ra_ide/src/syntax_highlighting/tests.rs
index 98c030791..110887c2a 100644
--- a/crates/ra_ide/src/syntax_highlighting/tests.rs
+++ b/crates/ra_ide/src/syntax_highlighting/tests.rs
@@ -131,3 +131,28 @@ fn test_ranges() {
 
     assert_eq!(&highlights[0].highlight.to_string(), "field.declaration");
 }
+
+#[test]
+fn test_flattening() {
+    let (analysis, file_id) = single_file(
+        r##"
+fn fixture(ra_fixture: &str) {}
+
+fn main() {
+    fixture(r#"
+        trait Foo {
+            fn foo() {
+                println!("2 + 2 = {}", 4);
+            }
+        }"#
+    );
+}"##
+        .trim(),
+    );
+
+    let dst_file = project_dir().join("crates/ra_ide/src/snapshots/highlight_injection.html");
+    let actual_html = &analysis.highlight_as_html(file_id, false).unwrap();
+    let expected_html = &read_text(&dst_file);
+    fs::write(dst_file, &actual_html).unwrap();
+    assert_eq_text!(expected_html, actual_html);
+}
diff --git a/crates/ra_mbe/src/tests.rs b/crates/ra_mbe/src/tests.rs
index a7fcea0ac..254318e23 100644
--- a/crates/ra_mbe/src/tests.rs
+++ b/crates/ra_mbe/src/tests.rs
@@ -1615,6 +1615,23 @@ fn test_issue_2520() {
 }
 
 #[test]
+fn test_issue_3861() {
+    let macro_fixture = parse_macro(
+        r#"
+        macro_rules! rgb_color {
+            ($p:expr, $t: ty) => {
+                pub fn new() {
+                    let _ = 0 as $t << $p;
+                }
+            };
+        }
+    "#,
+    );
+
+    macro_fixture.expand_items(r#"rgb_color!(8 + 8, u32);"#);
+}
+
+#[test]
 fn test_repeat_bad_var() {
     // FIXME: the second rule of the macro should be removed and an error about
     // `$( $c )+` raised
diff --git a/crates/ra_parser/src/grammar/types.rs b/crates/ra_parser/src/grammar/types.rs
index 2c00bce80..386969d2d 100644
--- a/crates/ra_parser/src/grammar/types.rs
+++ b/crates/ra_parser/src/grammar/types.rs
@@ -7,7 +7,7 @@ pub(super) const TYPE_FIRST: TokenSet = paths::PATH_FIRST.union(token_set![
     DYN_KW, L_ANGLE,
 ]);
 
-const TYPE_RECOVERY_SET: TokenSet = token_set![R_PAREN, COMMA];
+const TYPE_RECOVERY_SET: TokenSet = token_set![R_PAREN, COMMA, L_DOLLAR];
 
 pub(crate) fn type_(p: &mut Parser) {
     type_with_bounds_cond(p, true);
diff --git a/crates/ra_proc_macro_srv/src/proc_macro/diagnostic.rs b/crates/ra_proc_macro_srv/src/proc_macro/diagnostic.rs
index 9029f8815..55d93917c 100644
--- a/crates/ra_proc_macro_srv/src/proc_macro/diagnostic.rs
+++ b/crates/ra_proc_macro_srv/src/proc_macro/diagnostic.rs
@@ -54,12 +54,14 @@ pub struct Diagnostic {
 }
 
 macro_rules! diagnostic_child_methods {
-    ($spanned:ident, $regular:ident, $level:expr) => (
+    ($spanned:ident, $regular:ident, $level:expr) => {
         /// Adds a new child diagnostic message to `self` with the level
         /// identified by this method's name with the given `spans` and
         /// `message`.
         pub fn $spanned<S, T>(mut self, spans: S, message: T) -> Diagnostic
-            where S: MultiSpan, T: Into<String>
+        where
+            S: MultiSpan,
+            T: Into<String>,
         {
             self.children.push(Diagnostic::spanned(spans, $level, message));
             self
@@ -71,7 +73,7 @@ macro_rules! diagnostic_child_methods {
             self.children.push(Diagnostic::new($level, message));
             self
         }
-    )
+    };
 }
 
 /// Iterator over the children diagnostics of a `Diagnostic`.
diff --git a/crates/ra_proc_macro_srv/src/proc_macro/mod.rs b/crates/ra_proc_macro_srv/src/proc_macro/mod.rs
index e35a6ff8b..ee0dc9722 100644
--- a/crates/ra_proc_macro_srv/src/proc_macro/mod.rs
+++ b/crates/ra_proc_macro_srv/src/proc_macro/mod.rs
@@ -169,13 +169,13 @@ pub mod token_stream {
 pub struct Span(bridge::client::Span);
 
 macro_rules! diagnostic_method {
-    ($name:ident, $level:expr) => (
+    ($name:ident, $level:expr) => {
         /// Creates a new `Diagnostic` with the given `message` at the span
         /// `self`.
         pub fn $name<T: Into<String>>(self, message: T) -> Diagnostic {
             Diagnostic::spanned(self, $level, message)
         }
-    )
+    };
 }
 
 impl Span {
diff --git a/crates/ra_syntax/src/algo.rs b/crates/ra_syntax/src/algo.rs
index 191123c8e..8d1098036 100644
--- a/crates/ra_syntax/src/algo.rs
+++ b/crates/ra_syntax/src/algo.rs
@@ -316,7 +316,7 @@ impl<'a> SyntaxRewriter<'a> {
     }
 }
 
-impl<'a> ops::AddAssign for SyntaxRewriter<'_> {
+impl ops::AddAssign for SyntaxRewriter<'_> {
     fn add_assign(&mut self, rhs: SyntaxRewriter) {
         assert!(rhs.f.is_none());
         self.replacements.extend(rhs.replacements)