fix: Show what file paths were expected for unresolved modules

Author: Veykril

Cargo.lock

@@ -54,7 +54,7 @@ diagnostics![
 #[derive(Debug)]
 pub struct UnresolvedModule {
     pub decl: InFile<AstPtr<ast::Module>>,
-    pub candidate: String,
+    pub candidates: Box<[String]>,
 }
 
 #[derive(Debug)]

crates/hir/src/diagnostics.rs

@@ -593,12 +593,12 @@ impl Module {
 
 fn emit_def_diagnostic(db: &dyn HirDatabase, acc: &mut Vec<AnyDiagnostic>, diag: &DefDiagnostic) {
     match &diag.kind {
-        DefDiagnosticKind::UnresolvedModule { ast: declaration, candidate } => {
+        DefDiagnosticKind::UnresolvedModule { ast: declaration, candidates } => {
             let decl = declaration.to_node(db.upcast());
             acc.push(
                 UnresolvedModule {
                     decl: InFile::new(declaration.file_id, AstPtr::new(&decl)),
-                    candidate: candidate.clone(),
+                    candidates: candidates.clone(),
                 }
                 .into(),
             )

crates/hir/src/lib.rs

@@ -24,6 +24,7 @@ fst = { version = "0.4", default-features = false }
 itertools = "0.10.0"
 indexmap = "1.7.0"
 smallvec = "1.4.0"
+arrayvec = "0.7.2"
 la-arena = { version = "0.3.0", path = "../../lib/arena" }
 
 stdx = { path = "../stdx", version = "0.0.0" }

crates/hir_def/Cargo.toml

@@ -709,7 +709,7 @@ pub enum ModKind {
     Inline { items: Box<[ModItem]> },
 
     /// `mod m;`
-    Outline {},
+    Outline,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]

crates/hir_def/src/item_tree.rs

@@ -401,7 +401,7 @@ impl<'a> Ctx<'a> {
         let name = module.name()?.as_name();
         let visibility = self.lower_visibility(module);
         let kind = if module.semicolon_token().is_some() {
-            ModKind::Outline {}
+            ModKind::Outline
         } else {
             ModKind::Inline {
                 items: module

crates/hir_def/src/item_tree/lower.rs

@@ -423,7 +423,7 @@ impl<'a> Printer<'a> {
                         });
                         wln!(self, "}}");
                     }
-                    ModKind::Outline {} => {
+                    ModKind::Outline => {
                         wln!(self, ";");
                     }
                 }

crates/hir_def/src/item_tree/pretty.rs

@@ -1713,7 +1713,7 @@ impl ModCollector<'_, '_> {
                 }
             }
             // out of line module, resolve, parse and recurse
-            ModKind::Outline {} => {
+            ModKind::Outline => {
                 let ast_id = AstId::new(self.tree_id.file_id(), module.ast_id);
                 let db = self.def_collector.db;
                 match self.mod_dir.resolve_declaration(db, self.file_id(), &module.name, path_attr)
@@ -1751,9 +1751,9 @@ impl ModCollector<'_, '_> {
                             }
                         }
                     }
-                    Err(candidate) => {
+                    Err(candidates) => {
                         self.def_collector.def_map.diagnostics.push(
-                            DefDiagnostic::unresolved_module(self.module_id, ast_id, candidate),
+                            DefDiagnostic::unresolved_module(self.module_id, ast_id, candidates),
                         );
                     }
                 };

crates/hir_def/src/nameres/collector.rs

@@ -15,7 +15,7 @@ use crate::{
 
 #[derive(Debug, PartialEq, Eq)]
 pub enum DefDiagnosticKind {
-    UnresolvedModule { ast: AstId<ast::Module>, candidate: String },
+    UnresolvedModule { ast: AstId<ast::Module>, candidates: Box<[String]> },
 
     UnresolvedExternCrate { ast: AstId<ast::ExternCrate> },
 
@@ -46,11 +46,11 @@ impl DefDiagnostic {
     pub(super) fn unresolved_module(
         container: LocalModuleId,
         declaration: AstId<ast::Module>,
-        candidate: String,
+        candidates: Box<[String]>,
     ) -> Self {
         Self {
             in_module: container,
-            kind: DefDiagnosticKind::UnresolvedModule { ast: declaration, candidate },
+            kind: DefDiagnosticKind::UnresolvedModule { ast: declaration, candidates },
         }
     }
 

crates/hir_def/src/nameres/diagnostics.rs

@@ -1,4 +1,5 @@
 //! This module resolves `mod foo;` declaration to file.
+use arrayvec::ArrayVec;
 use base_db::{AnchoredPath, FileId};
 use hir_expand::name::Name;
 use limit::Limit;
@@ -63,22 +64,21 @@ impl ModDir {
         file_id: HirFileId,
         name: &Name,
         attr_path: Option<&SmolStr>,
-    ) -> Result<(FileId, bool, ModDir), String> {
+    ) -> Result<(FileId, bool, ModDir), Box<[String]>> {
         let orig_file_id = file_id.original_file(db.upcast());
 
-        let mut candidate_files = Vec::new();
+        let mut candidate_files = ArrayVec::<_, 2>::new();
         match attr_path {
             Some(attr_path) => {
                 candidate_files.push(self.dir_path.join_attr(attr_path, self.root_non_dir_owner))
             }
+            None if file_id.is_include_macro(db.upcast()) => {
+                candidate_files.push(format!("{}.rs", name));
+                candidate_files.push(format!("{}/mod.rs", name));
+            }
             None => {
-                if file_id.is_include_macro(db.upcast()) {
-                    candidate_files.push(format!("{}.rs", name));
-                    candidate_files.push(format!("{}/mod.rs", name));
-                } else {
-                    candidate_files.push(format!("{}{}.rs", self.dir_path.0, name));
-                    candidate_files.push(format!("{}{}/mod.rs", self.dir_path.0, name));
-                }
+                candidate_files.push(format!("{}{}.rs", self.dir_path.0, name));
+                candidate_files.push(format!("{}{}/mod.rs", self.dir_path.0, name));
             }
         };
 
@@ -97,7 +97,7 @@ impl ModDir {
                 }
             }
         }
-        Err(candidate_files.remove(0))
+        Err(candidate_files.into_iter().collect())
     }
 }