feat(semantic): check for invalid type import assignments (#4097)

Adds checks to `TSImportEqualsDeclaration` for invalid use of `import type` modifier.

```ts
import { Foo } from './foo'
namespace Bar {
  export class Baz {}
}

import type A = Foo.Baz;        // not allowed
import type B = Bar.Baz;        // not allowed
import type C = require('./c'); // allowed
```

crates/oxc_ast/src/ast_impl/ts.rs

@@ -194,6 +194,13 @@ impl<'a> TSModuleBlock<'a> {
     }
 }
 
+impl<'a> TSModuleReference<'a> {
+    /// Returns `true` if this is an [`TSModuleReference::ExternalModuleReference`].
+    pub fn is_external(&self) -> bool {
+        matches!(self, Self::ExternalModuleReference(_))
+    }
+}
+
 impl<'a> Decorator<'a> {
     /// Get the name of the decorator
     /// ```ts

crates/oxc_semantic/src/checker/mod.rs

@@ -99,6 +99,9 @@ pub fn check<'a>(node: &AstNode<'a>, ctx: &SemanticBuilder<'a>) {
         }
         AstKind::TSModuleDeclaration(decl) => ts::check_ts_module_declaration(decl, ctx),
         AstKind::TSEnumDeclaration(decl) => ts::check_ts_enum_declaration(decl, ctx),
+        AstKind::TSImportEqualsDeclaration(decl) => {
+            ts::check_ts_import_equals_declaration(decl, ctx);
+        }
         _ => {}
     }
 }

crates/oxc_semantic/src/checker/typescript.rs

@@ -168,3 +168,19 @@ pub fn check_ts_enum_declaration<'a>(decl: &TSEnumDeclaration<'a>, ctx: &Semanti
         }
     });
 }
+
+/// TS(1392)
+fn import_alias_cannot_use_import_type(span: Span) -> OxcDiagnostic {
+    OxcDiagnostic::error("TS(1392): An import alias cannot use 'import type'").with_label(span)
+}
+
+pub fn check_ts_import_equals_declaration<'a>(
+    decl: &TSImportEqualsDeclaration<'a>,
+    ctx: &SemanticBuilder<'a>,
+) {
+    // `import type Foo = require('./foo')` is allowed
+    // `import { Foo } from './foo'; import type Bar = Foo.Bar` is not allowed
+    if decl.import_kind.is_type() && !decl.module_reference.is_external() {
+        ctx.error(import_alias_cannot_use_import_type(decl.span));
+    }
+}

tasks/coverage/parser_babel.snap

@@ -3,7 +3,7 @@ commit: 12619ffe
 parser_babel Summary:
 AST Parsed     : 2093/2101 (99.62%)
 Positive Passed: 2083/2101 (99.14%)
-Negative Passed: 1371/1501 (91.34%)
+Negative Passed: 1373/1501 (91.47%)
 Expect Syntax Error: "annex-b/disabled/1.1-html-comments-close/input.js"
 Expect Syntax Error: "annex-b/disabled/3.1-sloppy-labeled-functions/input.js"
 Expect Syntax Error: "annex-b/disabled/3.1-sloppy-labeled-functions-if-body/input.js"
@@ -86,8 +86,6 @@ Expect Syntax Error: "typescript/expect-plugin/export-type-named/input.js"
 Expect Syntax Error: "typescript/export/equals-in-script/input.ts"
 Expect Syntax Error: "typescript/import/equals-in-script/input.ts"
 Expect Syntax Error: "typescript/import/equals-require-in-script/input.ts"
-Expect Syntax Error: "typescript/import/export-import-type/input.ts"
-Expect Syntax Error: "typescript/import/type-equals/input.ts"
 Expect Syntax Error: "typescript/interface/get-set-invalid-optional-parameter/input.ts"
 Expect Syntax Error: "typescript/interface/get-set-invalid-optional-parameter-babel-7/input.ts"
 Expect Syntax Error: "typescript/interface/get-set-invalid-parameters/input.ts"
@@ -10270,6 +10268,26 @@ Expect to Parse: "typescript/types/const-type-parameters-babel-7/input.ts"
    ·       ──
    ╰────
 
+  × TS(1392): An import alias cannot use 'import type'
+   ╭─[typescript/import/export-import-type/input.ts:1:8]
+ 1 │ export import type A = B.C;
+   ·        ────────────────────
+   ╰────
+
+  × TS(1392): An import alias cannot use 'import type'
+   ╭─[typescript/import/type-equals/input.ts:1:1]
+ 1 │ import type A = B.C;
+   · ────────────────────
+ 2 │ import type B = C;
+   ╰────
+
+  × TS(1392): An import alias cannot use 'import type'
+   ╭─[typescript/import/type-equals/input.ts:2:1]
+ 1 │ import type A = B.C;
+ 2 │ import type B = C;
+   · ──────────────────
+   ╰────
+
   × 'abstract' modifier cannot be used here.
    ╭─[typescript/interface/abstract/input.ts:1:1]
  1 │ abstract interface Foo {