internal: don't use #[should_panic] for tests

Author: matklad

crates/ide/src/goto_definition.rs

@@ -110,6 +110,13 @@ mod tests {
         assert_eq!(expected, FileRange { file_id: nav.file_id, range: nav.focus_or_full_range() });
     }
 
+    fn check_unresolved(ra_fixture: &str) {
+        let (analysis, position) = fixture::position(ra_fixture);
+        let navs = analysis.goto_definition(position).unwrap().expect("no definition found").info;
+
+        assert!(navs.is_empty(), "didn't expect this to resolve anywhere: {:?}", navs)
+    }
+
     #[test]
     fn goto_def_for_extern_crate() {
         check(
@@ -927,17 +934,12 @@ fn f() -> impl Iterator<Item$0 = u8> {}
     }
 
     #[test]
-    #[should_panic = "unresolved reference"]
     fn unknown_assoc_ty() {
-        check(
+        check_unresolved(
             r#"
-trait Iterator {
-    type Item;
-       //^^^^
-}
-
+trait Iterator { type Item; }
 fn f() -> impl Iterator<Invalid$0 = u8> {}
-            "#,
+"#,
         )
     }
 

crates/ide_assists/src/handlers/flip_comma.rs

@@ -66,26 +66,12 @@ mod tests {
     }
 
     #[test]
-    #[should_panic]
     fn flip_comma_before_punct() {
         // See https://github.com/rust-analyzer/rust-analyzer/issues/1619
         // "Flip comma" assist shouldn't be applicable to the last comma in enum or struct
         // declaration body.
-        check_assist_target(
-            flip_comma,
-            "pub enum Test { \
-             A,$0 \
-             }",
-            ",",
-        );
-
-        check_assist_target(
-            flip_comma,
-            "pub struct Test { \
-             foo: usize,$0 \
-             }",
-            ",",
-        );
+        check_assist_not_applicable(flip_comma, "pub enum Test { A,$0 }");
+        check_assist_not_applicable(flip_comma, "pub struct Test { foo: usize,$0 }");
     }
 
     #[test]

docs/dev/style.md

@@ -152,6 +152,16 @@ Do not reuse marks between several tests.
 
 **Rationale:** marks provide an easy way to find the canonical test for each bit of code.
 This makes it much easier to understand.
+More than one mark per test / code branch doesn't add significantly to understanding.
+
+## `#[should_panic]`
+
+Do not use `#[should_panic]` tests.
+Instead, explicitly check for `None`, `Err`, etc.
+
+**Rationale:**a `#[should_panic]` is a tool for library authors, to makes sure that API does not fail silently, when misused.
+`rust-analyzer` is not a library, we don't need to test for API misuse, and we have to handle any user input without panics.
+Panic messages in the logs from the `#[should_panic]` tests are confusing.
 
 ## Function Preconditions