path: root/crates/ra_hir_ty/src/expr.rs

//! FIXME: write short doc here

use std::sync::Arc;

use hir_def::{path::path, resolver::HasResolver, AdtId, FunctionId};
use hir_expand::diagnostics::DiagnosticSink;
use ra_syntax::{ast, AstPtr};
use rustc_hash::FxHashSet;

use crate::{
    db::HirDatabase,
    diagnostics::{MissingFields, MissingMatchArms, MissingOkInTailExpr, MissingPatFields},
    utils::variant_data,
    ApplicationTy, InferenceResult, Ty, TypeCtor,
    _match::{is_useful, MatchCheckCtx, Matrix, PatStack, Usefulness},
};

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,
    },
    LocalStructFieldId, VariantId,
};

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: &dyn HirDatabase) {
        let body = db.body(self.func.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,
                );
            }
            if let Expr::Match { expr, arms } = expr {
                self.validate_match(id, *expr, arms, db, self.infer.clone());
            }
        }
        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<LocalStructFieldId>,
    ) {
        // 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.as_ref().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,
                        })
                    }
                }
            }
        }
    }

    fn create_record_pattern_missing_fields_diagnostic(
        &mut self,
        id: PatId,
        db: &dyn HirDatabase,
        variant_def: VariantId,
        missed_fields: Vec<LocalStructFieldId>,
    ) {
        // 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.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(field_list) = record_pat.record_field_pat_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: AstPtr::new(&field_list),
                            missed_fields,
                        })
                    }
                }
            }
        }
    }

    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.func.into());

        let match_expr_ty = match infer.type_of_expr.get(match_expr) {
            Some(ty) => ty,
            // If we can't resolve the type of the match expression
            // we cannot perform exhaustiveness checks.
            None => return,
        };

        let cx = MatchCheckCtx { body, infer: infer.clone(), db };
        let pats = arms.iter().map(|arm| arm.pat);

        let mut seen = Matrix::empty();
        for pat in pats {
            // We skip any patterns whose type we cannot resolve.
            //
            // This could lead to false positives in this diagnostic, so
            // it might be better to skip the entire diagnostic if we either
            // cannot resolve a match arm or determine that the match arm has
            // the wrong type.
            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);
                }
            }
        }

        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) {
            if let Some(expr) = source_ptr.value.as_ref().left() {
                let root = source_ptr.file_syntax(db.upcast());
                if let ast::Expr::MatchExpr(match_expr) = expr.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 std_result_path = path![std::result::Result];

        let resolver = self.func.resolver(db.upcast());
        let std_result_enum = match resolver.resolve_known_enum(db.upcast(), &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 Ok(source_ptr) = source_map.expr_syntax(id) {
                if let Some(expr) = source_ptr.value.left() {
                    self.sink.push(MissingOkInTailExpr { file: source_ptr.file_id, expr });
                }
            }
        }
    }
}

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>, /*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<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, exhaustive))
}