feat: infer associate functions (#575)

Author: baszalmstra

crates/mun_hir/src/method_resolution.rs

@@ -161,7 +161,7 @@ impl InherentImpls {
         self.map.values().flatten().copied()
     }
 
-    // Returns all implementations defined for the specified type.
+    /// Returns all implementations defined for the specified type.
     pub fn for_self_ty(&self, self_ty: &Ty) -> &[ImplId] {
         match self_ty.interned() {
             TyKind::Struct(s) => self.map.get(&s.id).map_or(&[], AsRef::as_ref),

crates/mun_hir/src/ty/infer.rs

@@ -1,6 +1,7 @@
 use std::{ops::Index, sync::Arc};
 
 use la_arena::ArenaMap;
+use mun_hir_input::ModuleId;
 use rustc_hash::FxHashSet;
 
 use crate::{
@@ -24,8 +25,10 @@ mod unify;
 
 use crate::{
     expr::{LiteralFloat, LiteralFloatKind, LiteralInt, LiteralIntKind},
+    has_module::HasModule,
     ids::DefWithBodyId,
-    resolve::{resolver_for_expr, HasResolver},
+    method_resolution::lookup_method,
+    resolve::{resolver_for_expr, HasResolver, ResolveValueResult},
     ty::{
         primitives::{FloatTy, IntTy},
         TyKind,
@@ -184,6 +187,13 @@ impl<'a> InferenceResultBuilder<'a> {
         }
     }
 
+    /// Returns the module in which the body is defined.
+    pub fn module(&self) -> ModuleId {
+        match self.body.owner() {
+            DefWithBodyId::FunctionId(func) => func.module(self.db.upcast()),
+        }
+    }
+
     /// Associate the given `ExprId` with the specified `Ty`.
     fn set_expr_type(&mut self, expr: ExprId, ty: Ty) {
         self.type_of_expr.insert(expr, ty);
@@ -718,25 +728,73 @@ impl<'a> InferenceResultBuilder<'a> {
         }
     }
 
+    fn resolve_assoc_item(
+        &mut self,
+        def: TypeNs,
+        path: &Path,
+        remaining_index: usize,
+        id: ExprId,
+    ) -> Option<ValueNs> {
+        // We can only resolve the last element of the path.
+        let name = if remaining_index == path.segments.len() - 1 {
+            &path.segments[remaining_index]
+        } else {
+            return None;
+        };
+
+        // Infer the type of the definitions
+        let type_for_def_fn = |def| self.db.type_for_def(def, Namespace::Types);
+        let root_ty = match def {
+            TypeNs::SelfType(id) => self.db.type_for_impl_self(id),
+            TypeNs::StructId(id) => type_for_def_fn(TypableDef::Struct(id.into())),
+            TypeNs::TypeAliasId(id) => type_for_def_fn(TypableDef::TypeAlias(id.into())),
+            TypeNs::PrimitiveType(id) => type_for_def_fn(TypableDef::PrimitiveType(id)),
+        };
+
+        // Resolve the value.
+        let function_id = match lookup_method(self.db, &root_ty, self.module(), name) {
+            Ok(value) => value,
+            Err(Some(value)) => {
+                self.diagnostics
+                    .push(InferenceDiagnostic::PathIsPrivate { id });
+                value
+            }
+            _ => return None,
+        };
+
+        Some(ValueNs::FunctionId(function_id))
+    }
+
+    fn resolve_value_path_inner(
+        &mut self,
+        resolver: &Resolver,
+        path: &Path,
+        id: ExprId,
+    ) -> Option<ValueNs> {
+        let value_or_partial = resolver.resolve_path_as_value(self.db.upcast(), path)?;
+        match value_or_partial {
+            ResolveValueResult::ValueNs(it, vis) => {
+                if !vis.is_visible_from(self.db, self.module()) {
+                    self.diagnostics
+                        .push(diagnostics::InferenceDiagnostic::PathIsPrivate { id });
+                }
+
+                Some(it)
+            }
+            ResolveValueResult::Partial(def, remaining_index) => {
+                self.resolve_assoc_item(def, path, remaining_index, id)
+            }
+        }
+    }
+
     fn infer_path_expr(
         &mut self,
         resolver: &Resolver,
         path: &Path,
         id: ExprId,
         check_params: &CheckParams,
     ) -> Option<Ty> {
-        if let Some((value, vis)) = resolver.resolve_path_as_value_fully(self.db.upcast(), path) {
-            // Check visibility of this item
-            if !vis.is_visible_from(
-                self.db,
-                self.resolver
-                    .module()
-                    .expect("resolver must have a module to be able to resolve modules"),
-            ) {
-                self.diagnostics
-                    .push(diagnostics::InferenceDiagnostic::PathIsPrivate { id });
-            }
-
+        if let Some(value) = self.resolve_value_path_inner(resolver, path, id) {
             // Match based on what type of value we found
             match value {
                 ValueNs::ImplSelf(i) => {

crates/mun_hir/src/ty/snapshots/mun_hir__ty__tests__infer_access_hidden_assoc_function.snap

@@ -0,0 +1,9 @@
+---
+source: crates/mun_hir/src/ty/tests.rs
+expression: "infer(r#\"\n    //- /foo.mun\n    pub struct Foo {\n        a: i32\n    }\n\n    impl Foo {\n        fn new(){}\n    }\n\n    //- /mod.mun\n    fn main() {\n        foo::Foo::new();\n    }\n    \"#)"
+---
+16..29: access of private type
+10..34 '{     ...w(); }': ()
+16..29 'foo::Foo::new': function new() -> ()
+16..31 'foo::Foo::new()': ()
+54..56 '{}': ()

crates/mun_hir/src/ty/snapshots/mun_hir__ty__tests__infer_assoc_function.snap

@@ -0,0 +1,11 @@
+---
+source: crates/mun_hir/src/ty/tests.rs
+expression: "infer(r#\"\n    struct Foo {\n        a: i32\n    }\n\n    impl Foo {\n        fn new() -> Self {\n            Self { a: 3 }\n        }\n    }\n\n    fn main() {\n        let a = Foo::new();\n    }\n    \"#)"
+---
+102..129 '{     ...w(); }': ()
+112..113 'a': Foo
+116..124 'Foo::new': function new() -> Foo
+116..126 'Foo::new()': Foo
+59..88 '{     ...     }': Foo
+69..82 'Self { a: 3 }': Foo
+79..80 '3': i32

crates/mun_hir/src/ty/tests.rs

@@ -696,6 +696,48 @@ fn infer_self_field() {
     ));
 }
 
+#[test]
+fn infer_assoc_function() {
+    insta::assert_snapshot!(infer(
+        r#"
+    struct Foo {
+        a: i32
+    }
+
+    impl Foo {
+        fn new() -> Self {
+            Self { a: 3 }
+        }
+    }
+
+    fn main() {
+        let a = Foo::new();
+    }
+    "#
+    ));
+}
+
+#[test]
+fn infer_access_hidden_assoc_function() {
+    insta::assert_snapshot!(infer(
+        r#"
+    //- /foo.mun
+    pub struct Foo {
+        a: i32
+    }
+
+    impl Foo {
+        fn new(){}
+    }
+
+    //- /mod.mun
+    fn main() {
+        foo::Foo::new();
+    }
+    "#
+    ));
+}
+
 #[test]
 fn infer_basics() {
     insta::assert_snapshot!(infer(