Merge #1034

1034: HIR diagnostics API r=matklad a=matklad

This PR introduces diagnostics API for HIR, so we can now start issuing errors and warnings! Here are requirements that this solution aims to fulfill:

* structured diagnostics: rather than immediately rendering error to string, we provide a well-typed blob of data with error-description. These data is used by IDE to provide fixes
* open set diagnostics: there's no single enum with all possible diagnostics, which hopefully should result in better modularity

The `Diagnostic` trait describes "a diagnostic", which can be downcast to a specific diagnostic kind. Diagnostics are expressed in terms of macro-expanded syntax tree: they store pointers to syntax nodes. Diagnostics are self-contained: you don't need any context, besides `db`, to fully understand the meaning of a diagnostic. 

Because diagnostics are tied to the source, we can't store them in salsa. So subsystems like type-checking produce subsystem-local diagnostic (which is a closed `enum`), which is expressed in therms of subsystem IR. A separate step converts these proto-diagnostics into `Diagnostic`, by merging them with source-maps.

Note that this PR stresses type-system quite a bit: we now type-check every function in open files to compute errors!

Discussion on Zulip: https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Fwg-rls-2.2E0/topic/Diagnostics.20API

Co-authored-by: Aleksey Kladov <[email protected]>

2 files changed, 0 insertions, 44 deletions

diff --git a/crates/ra_ide_api/tests/test/main.rs b/crates/ra_ide_api/tests/test/main.rs
index 0f0766f62..d4ff21c09 100644
--- a/crates/ra_ide_api/tests/test/main.rs
+++ b/crates/ra_ide_api/tests/test/main.rs
@@ -1,4 +1,3 @@
-use insta::assert_debug_snapshot_matches;
 use ra_ide_api::{
     mock_analysis::{single_file, single_file_with_position, single_file_with_range, MockAnalysis},
     AnalysisChange, CrateGraph, Edition::Edition2018, Query, NavigationTarget,
@@ -7,21 +6,6 @@ use ra_ide_api::{
 use ra_syntax::SmolStr;
 
 #[test]
-fn test_unresolved_module_diagnostic() {
-    let (analysis, file_id) = single_file("mod foo;");
-    let diagnostics = analysis.diagnostics(file_id).unwrap();
-    assert_debug_snapshot_matches!("unresolved_module_diagnostic", &diagnostics);
-}
-
-// FIXME: move this test to hir
-#[test]
-fn test_unresolved_module_diagnostic_no_diag_for_inline_mode() {
-    let (analysis, file_id) = single_file("mod foo {}");
-    let diagnostics = analysis.diagnostics(file_id).unwrap();
-    assert!(diagnostics.is_empty());
-}
-
-#[test]
 fn test_resolve_crate_root() {
     let mock = MockAnalysis::with_files(
         "
diff --git a/crates/ra_ide_api/tests/test/snapshots/test__unresolved_module_diagnostic.snap b/crates/ra_ide_api/tests/test/snapshots/test__unresolved_module_diagnostic.snap
deleted file mode 100644
index 5bb953892..000000000
--- a/crates/ra_ide_api/tests/test/snapshots/test__unresolved_module_diagnostic.snap
+++ /dev/null
@@ -1,28 +0,0 @@
----
-created: "2019-01-22T14:45:01.486985900+00:00"
-creator: [email protected]
-expression: "&diagnostics"
-source: "crates\\ra_ide_api\\tests\\test\\main.rs"
----
-[
-    Diagnostic {
-        message: "unresolved module",
-        range: [0; 8),
-        fix: Some(
-            SourceChange {
-                label: "create module",
-                source_file_edits: [],
-                file_system_edits: [
-                    CreateFile {
-                        source_root: SourceRootId(
-                            0
-                        ),
-                        path: "foo.rs"
-                    }
-                ],
-                cursor_position: None
-            }
-        ),
-        severity: Error
-    }
-]