1 files changed, 129 insertions, 3 deletions

diff --git a/crates/ra_hir/src/expr.rs b/crates/ra_hir/src/expr.rs
index e4598eec0..e3733779e 100644
--- a/crates/ra_hir/src/expr.rs
+++ b/crates/ra_hir/src/expr.rs
@@ -1,12 +1,19 @@
 //! FIXME: write short doc here
 
-pub(crate) mod validation;
-
 use std::sync::Arc;
 
+use hir_def::path::known;
+use hir_expand::diagnostics::DiagnosticSink;
+use ra_syntax::ast;
 use ra_syntax::AstPtr;
+use rustc_hash::FxHashSet;
 
-use crate::{db::HirDatabase, DefWithBody, HasBody, Resolver};
+use crate::{
+    db::HirDatabase,
+    diagnostics::{MissingFields, MissingOkInTailExpr},
+    ty::{ApplicationTy, InferenceResult, Ty, TypeCtor},
+    Adt, DefWithBody, Function, HasBody, Name, Path, Resolver,
+};
 
 pub use hir_def::{
     body::{
@@ -42,3 +49,122 @@ pub(crate) fn resolver_for_scope(
     }
     r
 }
+
+pub(crate) struct ExprValidator<'a, 'b: 'a> {
+    func: Function,
+    infer: Arc<InferenceResult>,
+    sink: &'a mut DiagnosticSink<'b>,
+}
+
+impl<'a, 'b> ExprValidator<'a, 'b> {
+    pub(crate) fn new(
+        func: Function,
+        infer: Arc<InferenceResult>,
+        sink: &'a mut DiagnosticSink<'b>,
+    ) -> ExprValidator<'a, 'b> {
+        ExprValidator { func, infer, sink }
+    }
+
+    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::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(body.body_expr(), *t, db);
+        }
+    }
+
+    fn validate_record_literal(
+        &mut self,
+        id: ExprId,
+        _path: &Option<Path>,
+        fields: &[RecordLitField],
+        spread: Option<ExprId>,
+        db: &impl HirDatabase,
+    ) {
+        if spread.is_some() {
+            return;
+        }
+
+        let struct_def = match self.infer[id].as_adt() {
+            Some((Adt::Struct(s), _)) => s,
+            _ => return,
+        };
+
+        let lit_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect();
+        let missed_fields: Vec<Name> = struct_def
+            .fields(db)
+            .iter()
+            .filter_map(|f| {
+                let name = f.name(db);
+                if lit_fields.contains(&name) {
+                    None
+                } else {
+                    Some(name)
+                }
+            })
+            .collect();
+        if missed_fields.is_empty() {
+            return;
+        }
+        let source_map = self.func.body_source_map(db);
+
+        if let Some(source_ptr) = source_map.expr_syntax(id) {
+            if let Some(expr) = source_ptr.ast.a() {
+                let root = source_ptr.file_syntax(db);
+                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: &impl HirDatabase,
+    ) {
+        // the mismatch will be on the whole block currently
+        let mismatch = match self.infer.type_mismatch_for_expr(body_id) {
+            Some(m) => m,
+            None => return,
+        };
+
+        let std_result_path = known::std_result_result();
+
+        let resolver = self.func.resolver(db);
+        let std_result_enum = match resolver.resolve_known_enum(db, &std_result_path) {
+            Some(it) => it,
+            _ => return,
+        };
+
+        let std_result_ctor = TypeCtor::Adt(Adt::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);
+
+            if let Some(source_ptr) = source_map.expr_syntax(id) {
+                if let Some(expr) = source_ptr.ast.a() {
+                    self.sink.push(MissingOkInTailExpr { file: source_ptr.file_id, expr });
+                }
+            }
+        }
+    }
+}