diff --git a/crates/ide_completion/src/completions/fn_param.rs b/crates/ide_completion/src/completions/fn_param.rs
index d299f2e263..80ad3b9c8f 100644
--- a/crates/ide_completion/src/completions/fn_param.rs
+++ b/crates/ide_completion/src/completions/fn_param.rs
@@ -75,124 +75,3 @@ fn add_new_item_to_acc(
     item.kind(CompletionItemKind::Binding).lookup_by(lookup);
     item.add_to(acc)
 }
-
-#[cfg(test)]
-mod tests {
-    use expect_test::{expect, Expect};
-
-    use crate::{tests::filtered_completion_list, CompletionKind};
-
-    fn check(ra_fixture: &str, expect: Expect) {
-        let actual = filtered_completion_list(ra_fixture, CompletionKind::Magic);
-        expect.assert_eq(&actual);
-    }
-
-    #[test]
-    fn test_param_completion_last_param() {
-        check(
-            r#"
-fn foo(file_id: FileId) {}
-fn bar(file_id: FileId) {}
-fn baz(file$0) {}
-"#,
-            expect![[r#"
-                bn file_id: FileId
-            "#]],
-        );
-    }
-
-    #[test]
-    fn test_param_completion_first_param() {
-        check(
-            r#"
-fn foo(file_id: FileId) {}
-fn bar(file_id: FileId) {}
-fn baz(file$0 id: u32) {}
-"#,
-            expect![[r#"
-                bn file_id: FileId
-            "#]],
-        );
-    }
-
-    #[test]
-    fn test_param_completion_nth_param() {
-        check(
-            r#"
-fn foo(file_id: FileId) {}
-fn baz(file$0, x: i32) {}
-"#,
-            expect![[r#"
-                bn file_id: FileId
-            "#]],
-        );
-    }
-
-    #[test]
-    fn test_param_completion_trait_param() {
-        check(
-            r#"
-pub(crate) trait SourceRoot {
-    pub fn contains(&self, file_id: FileId) -> bool;
-    pub fn module_map(&self) -> &ModuleMap;
-    pub fn lines(&self, file_id: FileId) -> &LineIndex;
-    pub fn syntax(&self, file$0)
-}
-"#,
-            expect![[r#"
-                bn file_id: FileId
-            "#]],
-        );
-    }
-
-    #[test]
-    fn completes_param_in_inner_function() {
-        check(
-            r#"
-fn outer(text: String) {
-    fn inner($0)
-}
-"#,
-            expect![[r#"
-                bn text: String
-            "#]],
-        )
-    }
-
-    #[test]
-    fn completes_non_ident_pat_param() {
-        check(
-            r#"
-struct Bar { bar: u32 }
-
-fn foo(Bar { bar }: Bar) {}
-fn foo2($0) {}
-"#,
-            expect![[r#"
-                bn Bar { bar }: Bar
-            "#]],
-        )
-    }
-
-    #[test]
-    fn test_param_completion_self_param() {
-        check(
-            r#"
-                struct A {}
-
-                impl A {
-                    fn foo(file_id: FileId) {}
-                    fn new($0) {
-                    }
-                }
-            "#,
-            expect![[r#"
-                bn self
-                bn &self
-                bn mut self
-                bn &mut self
-                bn file_id: FileId
-            "#]],
-        )
-    }
-}
diff --git a/crates/ide_completion/src/tests.rs b/crates/ide_completion/src/tests.rs
index 3e65c65963..0b0c828617 100644
--- a/crates/ide_completion/src/tests.rs
+++ b/crates/ide_completion/src/tests.rs
@@ -5,6 +5,7 @@
 //! Notable examples for completions that are being tested in this module's submodule are paths.
 
 mod attribute;
+mod fn_param;
 mod item_list;
 mod item;
 mod pattern;
diff --git a/crates/ide_completion/src/tests/fn_param.rs b/crates/ide_completion/src/tests/fn_param.rs
new file mode 100644
index 0000000000..8a07aefafe
--- /dev/null
+++ b/crates/ide_completion/src/tests/fn_param.rs
@@ -0,0 +1,150 @@
+use expect_test::{expect, Expect};
+
+use crate::tests::completion_list;
+
+fn check(ra_fixture: &str, expect: Expect) {
+    let actual = completion_list(ra_fixture);
+    expect.assert_eq(&actual);
+}
+
+#[test]
+fn only_param() {
+    check(
+        r#"
+fn foo(file_id: usize) {}
+fn bar(file_id: usize) {}
+fn baz(file$0) {}
+"#,
+        expect![[r#"
+            bn file_id: usize
+            kw mut
+        "#]],
+    );
+}
+
+#[test]
+fn last_param() {
+    check(
+        r#"
+fn foo(file_id: usize) {}
+fn bar(file_id: usize) {}
+fn baz(foo: (), file$0) {}
+"#,
+        expect![[r#"
+            bn file_id: usize
+            kw mut
+        "#]],
+    );
+}
+
+#[test]
+fn first_param() {
+    check(
+        r#"
+fn foo(file_id: usize) {}
+fn bar(file_id: usize) {}
+fn baz(file$0 id: u32) {}
+"#,
+        expect![[r#"
+            bn file_id: usize
+            kw mut
+        "#]],
+    );
+}
+
+#[test]
+fn trait_param() {
+    check(
+        r#"
+pub(crate) trait SourceRoot {
+    pub fn contains(file_id: usize) -> bool;
+    pub fn syntax(file$0)
+}
+"#,
+        expect![[r#"
+            bn file_id: usize
+            kw mut
+        "#]],
+    );
+}
+
+#[test]
+fn in_inner_function() {
+    check(
+        r#"
+fn outer(text: &str) {
+    fn inner($0)
+}
+"#,
+        expect![[r#"
+            bn text: &str
+            kw mut
+        "#]],
+    )
+}
+
+#[test]
+fn shows_non_ident_pat_param() {
+    check(
+        r#"
+struct Bar { bar: u32 }
+fn foo(Bar { bar }: Bar) {}
+fn foo2($0) {}
+"#,
+        expect![[r#"
+            bn Bar { bar }: Bar
+            kw mut
+            bn Bar              Bar { bar$1 }: Bar$0
+            st Bar
+        "#]],
+    )
+}
+
+#[test]
+fn in_impl_only_param() {
+    check(
+        r#"
+struct A {}
+
+impl A {
+    fn foo(file_id: usize) {}
+    fn new($0) {}
+}
+"#,
+        expect![[r#"
+            bn self
+            bn &self
+            bn mut self
+            bn &mut self
+            bn file_id: usize
+            kw mut
+            sp Self
+            st A
+        "#]],
+    )
+}
+
+#[test]
+fn in_impl_after_self() {
+    // FIXME: self completions should not be here
+    check(
+        r#"
+struct A {}
+
+impl A {
+    fn foo(file_id: usize) {}
+    fn new(self, $0) {}
+}
+"#,
+        expect![[r#"
+            bn self
+            bn &self
+            bn mut self
+            bn &mut self
+            bn file_id: usize
+            kw mut
+            sp Self
+            st A
+        "#]],
+    )
+}
diff --git a/crates/ide_db/src/call_info.rs b/crates/ide_db/src/call_info.rs
index da3b9bf1e9..4795e25650 100644
--- a/crates/ide_db/src/call_info.rs
+++ b/crates/ide_db/src/call_info.rs
@@ -166,7 +166,7 @@ impl ActiveParameter {
 
         let idx = active_parameter?;
         let mut params = signature.params(sema.db);
-        if params.len() <= idx {
+        if !(idx < params.len()) {
             cov_mark::hit!(too_many_arguments);
             return None;
         }