1 files changed, 58 insertions, 11 deletions

diff --git a/crates/ra_hir/src/expr/validation.rs b/crates/ra_hir/src/expr/validation.rs
index 82a06ca25..5d9d59ff8 100644
--- a/crates/ra_hir/src/expr/validation.rs
+++ b/crates/ra_hir/src/expr/validation.rs
@@ -1,16 +1,19 @@
 use rustc_hash::FxHashSet;
 use std::sync::Arc;
 
-use ra_syntax::ast::{AstNode, StructLit};
+use ra_syntax::ast::{AstNode, RecordLit};
 
-use super::{Expr, ExprId, StructLitField};
+use super::{Expr, ExprId, RecordLitField};
 use crate::{
     adt::AdtDef,
-    diagnostics::{DiagnosticSink, MissingFields},
+    diagnostics::{DiagnosticSink, MissingFields, MissingOkInTailExpr},
     expr::AstPtr,
-    ty::InferenceResult,
-    Function, HasSource, HirDatabase, Name, Path,
+    name,
+    path::{PathKind, PathSegment},
+    ty::{ApplicationTy, InferenceResult, Ty, TypeCtor},
+    Function, HasSource, HirDatabase, ModuleDef, Name, Path, PerNs, Resolution,
 };
+use ra_syntax::ast;
 
 pub(crate) struct ExprValidator<'a, 'b: 'a> {
     func: Function,
@@ -29,18 +32,24 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
 
     pub(crate) fn validate_body(&mut self, db: &impl HirDatabase) {
         let body = self.func.body(db);
+
         for e in body.exprs() {
-            if let (id, Expr::StructLit { path, fields, spread }) = e {
-                self.validate_struct_literal(id, path, fields, *spread, db);
+            if let (id, Expr::RecordLit { path, fields, spread }) = e {
+                self.validate_record_literal(id, path, fields, *spread, db);
             }
         }
+
+        let body_expr = &body[body.body_expr()];
+        if let Expr::Block { statements: _, tail: Some(t) } = body_expr {
+            self.validate_results_in_tail_expr(*t, db);
+        }
     }
 
-    fn validate_struct_literal(
+    fn validate_record_literal(
         &mut self,
         id: ExprId,
         _path: &Option<Path>,
-        fields: &[StructLitField],
+        fields: &[RecordLitField],
         spread: Option<ExprId>,
         db: &impl HirDatabase,
     ) {
@@ -76,8 +85,8 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         if let Some(field_list_node) = source_map
             .expr_syntax(id)
             .map(|ptr| ptr.to_node(source_file.syntax()))
-            .and_then(StructLit::cast)
-            .and_then(|lit| lit.named_field_list())
+            .and_then(RecordLit::cast)
+            .and_then(|lit| lit.record_field_list())
         {
             let field_list_ptr = AstPtr::new(&field_list_node);
             self.sink.push(MissingFields {
@@ -87,4 +96,42 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             })
         }
     }
+
+    fn validate_results_in_tail_expr(&mut self, id: ExprId, db: &impl HirDatabase) {
+        let mismatch = match self.infer.type_mismatch_for_expr(id) {
+            Some(m) => m,
+            None => return,
+        };
+
+        let std_result_path = Path {
+            kind: PathKind::Abs,
+            segments: vec![
+                PathSegment { name: name::STD, args_and_bindings: None },
+                PathSegment { name: name::RESULT_MOD, args_and_bindings: None },
+                PathSegment { name: name::RESULT_TYPE, args_and_bindings: None },
+            ],
+        };
+
+        let resolver = self.func.resolver(db);
+        let std_result_enum =
+            match resolver.resolve_path_segments(db, &std_result_path).into_fully_resolved() {
+                PerNs { types: Some(Resolution::Def(ModuleDef::Enum(e))), .. } => e,
+                _ => return,
+            };
+
+        let std_result_ctor = TypeCtor::Adt(AdtDef::Enum(std_result_enum));
+        let params = match &mismatch.expected {
+            Ty::Apply(ApplicationTy { ctor, parameters }) if ctor == &std_result_ctor => parameters,
+            _ => return,
+        };
+
+        if params.len() == 2 && &params[0] == &mismatch.actual {
+            let source_map = self.func.body_source_map(db);
+            let file_id = self.func.source(db).file_id;
+
+            if let Some(expr) = source_map.expr_syntax(id).and_then(|n| n.cast::<ast::Expr>()) {
+                self.sink.push(MissingOkInTailExpr { file: file_id, expr });
+            }
+        }
+    }
 }