1 files changed, 569 insertions, 0 deletions

diff --git a/crates/hir_ty/src/diagnostics/expr.rs b/crates/hir_ty/src/diagnostics/expr.rs
new file mode 100644
index 000000000..278a4b947
--- /dev/null
+++ b/crates/hir_ty/src/diagnostics/expr.rs
@@ -0,0 +1,569 @@
+//! FIXME: write short doc here
+
+use std::sync::Arc;
+
+use hir_def::{path::path, resolver::HasResolver, AdtId, DefWithBodyId};
+use hir_expand::diagnostics::DiagnosticSink;
+use rustc_hash::FxHashSet;
+use syntax::{ast, AstPtr};
+
+use crate::{
+    db::HirDatabase,
+    diagnostics::{
+        match_check::{is_useful, MatchCheckCtx, Matrix, PatStack, Usefulness},
+        MismatchedArgCount, MissingFields, MissingMatchArms, MissingOkInTailExpr, MissingPatFields,
+    },
+    utils::variant_data,
+    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,
+    },
+    src::HasSource,
+    LocalFieldId, Lookup, VariantId,
+};
+
+pub(super) struct ExprValidator<'a, 'b: 'a> {
+    owner: DefWithBodyId,
+    infer: Arc<InferenceResult>,
+    sink: &'a mut DiagnosticSink<'b>,
+}
+
+impl<'a, 'b> ExprValidator<'a, 'b> {
+    pub(super) fn new(
+        owner: DefWithBodyId,
+        infer: Arc<InferenceResult>,
+        sink: &'a mut DiagnosticSink<'b>,
+    ) -> ExprValidator<'a, 'b> {
+        ExprValidator { owner, infer, sink }
+    }
+
+    pub(super) fn validate_body(&mut self, db: &dyn HirDatabase) {
+        let body = db.body(self.owner.into());
+
+        for (id, expr) in body.exprs.iter() {
+            if let Some((variant_def, missed_fields, true)) =
+                record_literal_missing_fields(db, &self.infer, id, expr)
+            {
+                self.create_record_literal_missing_fields_diagnostic(
+                    id,
+                    db,
+                    variant_def,
+                    missed_fields,
+                );
+            }
+
+            match expr {
+                Expr::Match { expr, arms } => {
+                    self.validate_match(id, *expr, arms, db, self.infer.clone());
+                }
+                Expr::Call { .. } | Expr::MethodCall { .. } => {
+                    self.validate_call(db, id, expr);
+                }
+                _ => {}
+            }
+        }
+        for (id, pat) in body.pats.iter() {
+            if let Some((variant_def, missed_fields, true)) =
+                record_pattern_missing_fields(db, &self.infer, id, pat)
+            {
+                self.create_record_pattern_missing_fields_diagnostic(
+                    id,
+                    db,
+                    variant_def,
+                    missed_fields,
+                );
+            }
+        }
+        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);
+        }
+    }
+
+    fn create_record_literal_missing_fields_diagnostic(
+        &mut self,
+        id: ExprId,
+        db: &dyn HirDatabase,
+        variant_def: VariantId,
+        missed_fields: Vec<LocalFieldId>,
+    ) {
+        // XXX: only look at source_map if we do have missing fields
+        let (_, source_map) = db.body_with_source_map(self.owner.into());
+
+        if let Ok(source_ptr) = source_map.expr_syntax(id) {
+            let root = source_ptr.file_syntax(db.upcast());
+            if let ast::Expr::RecordExpr(record_expr) = &source_ptr.value.to_node(&root) {
+                if let Some(_) = record_expr.record_expr_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_parent: AstPtr::new(&record_expr),
+                        field_list_parent_path: record_expr.path().map(|path| AstPtr::new(&path)),
+                        missed_fields,
+                    })
+                }
+            }
+        }
+    }
+
+    fn create_record_pattern_missing_fields_diagnostic(
+        &mut self,
+        id: PatId,
+        db: &dyn HirDatabase,
+        variant_def: VariantId,
+        missed_fields: Vec<LocalFieldId>,
+    ) {
+        // XXX: only look at source_map if we do have missing fields
+        let (_, source_map) = db.body_with_source_map(self.owner.into());
+
+        if let Ok(source_ptr) = source_map.pat_syntax(id) {
+            if let Some(expr) = source_ptr.value.as_ref().left() {
+                let root = source_ptr.file_syntax(db.upcast());
+                if let ast::Pat::RecordPat(record_pat) = expr.to_node(&root) {
+                    if let Some(_) = record_pat.record_pat_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(MissingPatFields {
+                            file: source_ptr.file_id,
+                            field_list_parent: AstPtr::new(&record_pat),
+                            field_list_parent_path: record_pat
+                                .path()
+                                .map(|path| AstPtr::new(&path)),
+                            missed_fields,
+                        })
+                    }
+                }
+            }
+        }
+    }
+
+    fn validate_call(&mut self, db: &dyn HirDatabase, call_id: ExprId, expr: &Expr) -> Option<()> {
+        // Check that the number of arguments matches the number of parameters.
+
+        // FIXME: Due to shortcomings in the current type system implementation, only emit this
+        // diagnostic if there are no type mismatches in the containing function.
+        if self.infer.type_mismatches.iter().next().is_some() {
+            return Some(());
+        }
+
+        let is_method_call = matches!(expr, Expr::MethodCall { .. });
+        let (sig, args) = match expr {
+            Expr::Call { callee, args } => {
+                let callee = &self.infer.type_of_expr[*callee];
+                let sig = callee.callable_sig(db)?;
+                (sig, args.clone())
+            }
+            Expr::MethodCall { receiver, args, .. } => {
+                let mut args = args.clone();
+                args.insert(0, *receiver);
+
+                // FIXME: note that we erase information about substs here. This
+                // is not right, but, luckily, doesn't matter as we care only
+                // about the number of params
+                let callee = self.infer.method_resolution(call_id)?;
+                let sig = db.callable_item_signature(callee.into()).value;
+
+                (sig, args)
+            }
+            _ => return None,
+        };
+
+        if sig.is_varargs {
+            return None;
+        }
+
+        let params = sig.params();
+
+        let mut param_count = params.len();
+        let mut arg_count = args.len();
+
+        if arg_count != param_count {
+            let (_, source_map) = db.body_with_source_map(self.owner.into());
+            if let Ok(source_ptr) = source_map.expr_syntax(call_id) {
+                if is_method_call {
+                    param_count -= 1;
+                    arg_count -= 1;
+                }
+                self.sink.push(MismatchedArgCount {
+                    file: source_ptr.file_id,
+                    call_expr: source_ptr.value,
+                    expected: param_count,
+                    found: arg_count,
+                });
+            }
+        }
+
+        None
+    }
+
+    fn validate_match(
+        &mut self,
+        id: ExprId,
+        match_expr: ExprId,
+        arms: &[MatchArm],
+        db: &dyn HirDatabase,
+        infer: Arc<InferenceResult>,
+    ) {
+        let (body, source_map): (Arc<Body>, Arc<BodySourceMap>) =
+            db.body_with_source_map(self.owner.into());
+
+        let match_expr_ty = match infer.type_of_expr.get(match_expr) {
+            // If we can't resolve the type of the match expression
+            // we cannot perform exhaustiveness checks.
+            None | Some(Ty::Unknown) => return,
+            Some(ty) => ty,
+        };
+
+        let cx = MatchCheckCtx { match_expr, body, infer: infer.clone(), db };
+        let pats = arms.iter().map(|arm| arm.pat);
+
+        let mut seen = Matrix::empty();
+        for pat in pats {
+            if let Some(pat_ty) = infer.type_of_pat.get(pat) {
+                // We only include patterns whose type matches the type
+                // of the match expression. If we had a InvalidMatchArmPattern
+                // diagnostic or similar we could raise that in an else
+                // block here.
+                //
+                // When comparing the types, we also have to consider that rustc
+                // will automatically de-reference the match expression type if
+                // necessary.
+                //
+                // FIXME we should use the type checker for this.
+                if pat_ty == match_expr_ty
+                    || match_expr_ty
+                        .as_reference()
+                        .map(|(match_expr_ty, _)| match_expr_ty == pat_ty)
+                        .unwrap_or(false)
+                {
+                    // If we had a NotUsefulMatchArm diagnostic, we could
+                    // check the usefulness of each pattern as we added it
+                    // to the matrix here.
+                    let v = PatStack::from_pattern(pat);
+                    seen.push(&cx, v);
+                    continue;
+                }
+            }
+
+            // If we can't resolve the type of a pattern, or the pattern type doesn't
+            // fit the match expression, we skip this diagnostic. Skipping the entire
+            // diagnostic rather than just not including this match arm is preferred
+            // to avoid the chance of false positives.
+            return;
+        }
+
+        match is_useful(&cx, &seen, &PatStack::from_wild()) {
+            Ok(Usefulness::Useful) => (),
+            // if a wildcard pattern is not useful, then all patterns are covered
+            Ok(Usefulness::NotUseful) => return,
+            // this path is for unimplemented checks, so we err on the side of not
+            // reporting any errors
+            _ => return,
+        }
+
+        if let Ok(source_ptr) = source_map.expr_syntax(id) {
+            let root = source_ptr.file_syntax(db.upcast());
+            if let ast::Expr::MatchExpr(match_expr) = &source_ptr.value.to_node(&root) {
+                if let (Some(match_expr), Some(arms)) =
+                    (match_expr.expr(), match_expr.match_arm_list())
+                {
+                    self.sink.push(MissingMatchArms {
+                        file: source_ptr.file_id,
+                        match_expr: AstPtr::new(&match_expr),
+                        arms: AstPtr::new(&arms),
+                    })
+                }
+            }
+        }
+    }
+
+    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) {
+            Some(m) => m,
+            None => return,
+        };
+
+        let core_result_path = path![core::result::Result];
+
+        let resolver = self.owner.resolver(db.upcast());
+        let core_result_enum = match resolver.resolve_known_enum(db.upcast(), &core_result_path) {
+            Some(it) => it,
+            _ => return,
+        };
+
+        let core_result_ctor = TypeCtor::Adt(AdtId::EnumId(core_result_enum));
+        let params = match &mismatch.expected {
+            Ty::Apply(ApplicationTy { ctor, parameters }) if ctor == &core_result_ctor => {
+                parameters
+            }
+            _ => return,
+        };
+
+        if params.len() == 2 && params[0] == mismatch.actual {
+            let (_, source_map) = db.body_with_source_map(self.owner.into());
+
+            if let Ok(source_ptr) = source_map.expr_syntax(id) {
+                self.sink
+                    .push(MissingOkInTailExpr { file: source_ptr.file_id, expr: source_ptr.value });
+            }
+        }
+    }
+}
+
+pub fn record_literal_missing_fields(
+    db: &dyn HirDatabase,
+    infer: &InferenceResult,
+    id: ExprId,
+    expr: &Expr,
+) -> Option<(VariantId, Vec<LocalFieldId>, /*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<LocalFieldId> = 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<LocalFieldId>, /*exhaustive*/ bool)> {
+    let (fields, exhaustive) = match pat {
+        Pat::Record { path: _, args, ellipsis } => (args, !ellipsis),
+        _ => 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<LocalFieldId> = 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, exhaustive))
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::diagnostics::tests::check_diagnostics;
+
+    #[test]
+    fn simple_free_fn_zero() {
+        check_diagnostics(
+            r#"
+fn zero() {}
+fn f() { zero(1); }
+       //^^^^^^^ Expected 0 arguments, found 1
+"#,
+        );
+
+        check_diagnostics(
+            r#"
+fn zero() {}
+fn f() { zero(); }
+"#,
+        );
+    }
+
+    #[test]
+    fn simple_free_fn_one() {
+        check_diagnostics(
+            r#"
+fn one(arg: u8) {}
+fn f() { one(); }
+       //^^^^^ Expected 1 argument, found 0
+"#,
+        );
+
+        check_diagnostics(
+            r#"
+fn one(arg: u8) {}
+fn f() { one(1); }
+"#,
+        );
+    }
+
+    #[test]
+    fn method_as_fn() {
+        check_diagnostics(
+            r#"
+struct S;
+impl S { fn method(&self) {} }
+
+fn f() {
+    S::method();
+} //^^^^^^^^^^^ Expected 1 argument, found 0
+"#,
+        );
+
+        check_diagnostics(
+            r#"
+struct S;
+impl S { fn method(&self) {} }
+
+fn f() {
+    S::method(&S);
+    S.method();
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn method_with_arg() {
+        check_diagnostics(
+            r#"
+struct S;
+impl S { fn method(&self, arg: u8) {} }
+
+            fn f() {
+                S.method();
+            } //^^^^^^^^^^ Expected 1 argument, found 0
+            "#,
+        );
+
+        check_diagnostics(
+            r#"
+struct S;
+impl S { fn method(&self, arg: u8) {} }
+
+fn f() {
+    S::method(&S, 0);
+    S.method(1);
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn tuple_struct() {
+        check_diagnostics(
+            r#"
+struct Tup(u8, u16);
+fn f() {
+    Tup(0);
+} //^^^^^^ Expected 2 arguments, found 1
+"#,
+        )
+    }
+
+    #[test]
+    fn enum_variant() {
+        check_diagnostics(
+            r#"
+enum En { Variant(u8, u16), }
+fn f() {
+    En::Variant(0);
+} //^^^^^^^^^^^^^^ Expected 2 arguments, found 1
+"#,
+        )
+    }
+
+    #[test]
+    fn enum_variant_type_macro() {
+        check_diagnostics(
+            r#"
+macro_rules! Type {
+    () => { u32 };
+}
+enum Foo {
+    Bar(Type![])
+}
+impl Foo {
+    fn new() {
+        Foo::Bar(0);
+        Foo::Bar(0, 1);
+      //^^^^^^^^^^^^^^ Expected 1 argument, found 2
+        Foo::Bar();
+      //^^^^^^^^^^ Expected 1 argument, found 0
+    }
+}
+        "#,
+        );
+    }
+
+    #[test]
+    fn varargs() {
+        check_diagnostics(
+            r#"
+extern "C" {
+    fn fixed(fixed: u8);
+    fn varargs(fixed: u8, ...);
+    fn varargs2(...);
+}
+
+fn f() {
+    unsafe {
+        fixed(0);
+        fixed(0, 1);
+      //^^^^^^^^^^^ Expected 1 argument, found 2
+        varargs(0);
+        varargs(0, 1);
+        varargs2();
+        varargs2(0);
+        varargs2(0, 1);
+    }
+}
+        "#,
+        )
+    }
+
+    #[test]
+    fn arg_count_lambda() {
+        check_diagnostics(
+            r#"
+fn main() {
+    let f = |()| ();
+    f();
+  //^^^ Expected 1 argument, found 0
+    f(());
+    f((), ());
+  //^^^^^^^^^ Expected 1 argument, found 2
+}
+"#,
+        )
+    }
+}