Hide alias (#4432)

* Add alias interning

Now, AliasId is used to reference aliases stored in EngineState, similar
to decls, blocks, etc.

* Fix wrong message

* Fix using decl instead of alias

* Extend also alias id visibility

* Merge also aliases from delta

* Add alias hiding code

Does not work yet but passes tests at least.

* Fix wrong alias lookup and visibility appending

* Add hide alias tests

* Fmt & Clippy

* Fix random clippy warnings in "which" command

src/tests/test_hiding.rs

@@ -9,6 +9,14 @@ fn hides_def() -> TestResult {
     )
 }
 
+#[test]
+fn hides_alias() -> TestResult {
+    fail_test(
+        r#"alias foo = echo "foo"; hide foo; foo"#,
+        "", // we just care if it errors
+    )
+}
+
 #[test]
 fn hides_env() -> TestResult {
     fail_test(r#"let-env foo = "foo"; hide foo; $env.foo"#, "did you mean")
@@ -24,6 +32,14 @@ fn hides_def_then_redefines() -> TestResult {
     )
 }
 
+#[test]
+fn hides_alias_then_redefines() -> TestResult {
+    run_test(
+        r#"alias foo = echo "foo"; hide foo; alias foo = echo "foo"; foo"#,
+        "foo",
+    )
+}
+
 #[test]
 fn hides_env_then_redefines() -> TestResult {
     run_test(
@@ -64,6 +80,38 @@ fn hides_def_in_scope_4() -> TestResult {
     )
 }
 
+#[test]
+fn hides_alias_in_scope_1() -> TestResult {
+    fail_test(
+        r#"alias foo = echo "foo"; do { hide foo; foo }"#,
+        "", // we just care if it errors
+    )
+}
+
+#[test]
+fn hides_alias_in_scope_2() -> TestResult {
+    run_test(
+        r#"alias foo = echo "foo"; do { alias foo = echo "bar"; hide foo; foo }"#,
+        "foo",
+    )
+}
+
+#[test]
+fn hides_alias_in_scope_3() -> TestResult {
+    fail_test(
+        r#"alias foo = echo "foo"; do { hide foo; alias foo = echo "bar"; hide foo; foo }"#,
+        "", // we just care if it errors
+    )
+}
+
+#[test]
+fn hides_alias_in_scope_4() -> TestResult {
+    fail_test(
+        r#"alias foo = echo "foo"; do { alias foo = echo "bar"; hide foo; hide foo; foo }"#,
+        "", // we just care if it errors
+    )
+}
+
 #[test]
 fn hides_env_in_scope_1() -> TestResult {
     fail_test(
@@ -104,6 +152,14 @@ fn hide_def_twice_not_allowed() -> TestResult {
     )
 }
 
+#[test]
+fn hide_alias_twice_not_allowed() -> TestResult {
+    fail_test(
+        r#"alias foo = echo "foo"; hide foo; hide foo"#,
+        "did not find",
+    )
+}
+
 #[test]
 fn hide_env_twice_not_allowed() -> TestResult {
     fail_test(r#"let-env foo = "foo"; hide foo; hide foo"#, "did not find")
@@ -125,6 +181,38 @@ fn hides_def_runs_env_2() -> TestResult {
     )
 }
 
+#[test]
+fn hides_alias_runs_def_1() -> TestResult {
+    run_test(
+        r#"def foo [] { "bar" }; alias foo = echo "foo"; hide foo; foo"#,
+        "bar",
+    )
+}
+
+#[test]
+fn hides_alias_runs_def_2() -> TestResult {
+    run_test(
+        r#"alias foo = echo "foo"; def foo [] { "bar" }; hide foo; foo"#,
+        "bar",
+    )
+}
+
+#[test]
+fn hides_alias_runs_env_1() -> TestResult {
+    run_test(
+        r#"let-env foo = "bar"; alias foo = echo "foo"; hide foo; $env.foo"#,
+        "bar",
+    )
+}
+
+#[test]
+fn hides_alias_runs_env_2() -> TestResult {
+    run_test(
+        r#"alias foo = echo "foo"; let-env foo = "bar"; hide foo; $env.foo"#,
+        "bar",
+    )
+}
+
 #[test]
 fn hides_def_and_env() -> TestResult {
     fail_test(
@@ -133,6 +221,30 @@ fn hides_def_and_env() -> TestResult {
     )
 }
 
+#[test]
+fn hides_alias_and_def() -> TestResult {
+    fail_test(
+        r#"alias foo = echo "foo"; def foo [] { "bar" }; hide foo; hide foo; foo"#,
+        "", // we just care if it errors
+    )
+}
+
+#[test]
+fn hides_alias_def_and_env_1() -> TestResult {
+    fail_test(
+        r#"alias foo = echo "foo"; def foo [] { "foo" }; let-env foo = "bar"; hide foo; hide foo; hide foo; $env.foo"#,
+        "", // we just care if it errors
+    )
+}
+
+#[test]
+fn hides_alias_def_and_env_2() -> TestResult {
+    fail_test(
+        r#"alias foo = echo "foo"; def foo [] { "foo" }; let-env foo = "bar"; hide foo; hide foo; hide foo; foo"#,
+        "", // we just care if it errors
+    )
+}
+
 #[test]
 fn hides_def_import_1() -> TestResult {
     fail_test(