1 files changed, 151 insertions, 0 deletions

diff --git a/crates/ra_hir_ty/src/expr.rs b/crates/ra_hir_ty/src/expr.rs
new file mode 100644
index 000000000..5c65f9370
--- /dev/null
+++ b/crates/ra_hir_ty/src/expr.rs
@@ -0,0 +1,151 @@
+//! FIXME: write short doc here
+
+use std::sync::Arc;
+
+use hir_def::{
+    path::{known, Path},
+    resolver::HasResolver,
+    AdtId, FunctionId,
+};
+use hir_expand::{diagnostics::DiagnosticSink, name::Name};
+use ra_syntax::ast;
+use ra_syntax::AstPtr;
+use rustc_hash::FxHashSet;
+
+use crate::{
+    db::HirDatabase,
+    diagnostics::{MissingFields, MissingOkInTailExpr},
+    ApplicationTy, InferenceResult, Ty, TypeCtor,
+};
+
+pub use hir_def::{
+    body::{
+        scope::{ExprScopes, ScopeEntry, ScopeId},
+        Body, BodySourceMap, ExprPtr, ExprSource, PatPtr, PatSource,
+    },
+    expr::{
+        ArithOp, Array, BinaryOp, BindingAnnotation, CmpOp, Expr, ExprId, Literal, LogicOp,
+        MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField, Statement, UnaryOp,
+    },
+};
+
+pub struct ExprValidator<'a, 'b: 'a> {
+    func: FunctionId,
+    infer: Arc<InferenceResult>,
+    sink: &'a mut DiagnosticSink<'b>,
+}
+
+impl<'a, 'b> ExprValidator<'a, 'b> {
+    pub fn new(
+        func: FunctionId,
+        infer: Arc<InferenceResult>,
+        sink: &'a mut DiagnosticSink<'b>,
+    ) -> ExprValidator<'a, 'b> {
+        ExprValidator { func, infer, sink }
+    }
+
+    pub fn validate_body(&mut self, db: &impl 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);
+            }
+        }
+
+        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((AdtId::StructId(s), _)) => s,
+            _ => return,
+        };
+        let struct_data = db.struct_data(struct_def);
+
+        let lit_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect();
+        let missed_fields: Vec<Name> = struct_data
+            .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 Some(source_ptr) = source_map.expr_syntax(id) {
+            if let Some(expr) = source_ptr.value.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(AdtId::EnumId(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) = db.body_with_source_map(self.func.into());
+
+            if let Some(source_ptr) = source_map.expr_syntax(id) {
+                if let Some(expr) = source_ptr.value.a() {
+                    self.sink.push(MissingOkInTailExpr { file: source_ptr.file_id, expr });
+                }
+            }
+        }
+    }
+}