fix(es/resolver): Use type context for export = if it's unresolved (#6963)

**Related issue:**

 - dudykr/stc#717.

Author: kdy1

crates/swc_ecma_transforms_base/src/resolver/mod.rs

@@ -1222,6 +1222,16 @@ impl<'a> VisitMut for Resolver<'a> {
         });
     }
 
+    fn visit_mut_ts_export_assignment(&mut self, node: &mut TsExportAssignment) {
+        node.expr.visit_mut_with(self);
+
+        if self.config.handle_types {
+            if let Some(i) = leftmost(&mut node.expr) {
+                self.try_resolving_as_type(i);
+            }
+        }
+    }
+
     fn visit_mut_ts_expr_with_type_args(&mut self, n: &mut TsExprWithTypeArgs) {
         if self.config.handle_types {
             let old = self.in_type;
@@ -1453,6 +1463,15 @@ impl<'a> VisitMut for Resolver<'a> {
     }
 }
 
+fn leftmost(expr: &mut Expr) -> Option<&mut Ident> {
+    match expr {
+        Expr::Ident(i) => Some(i),
+        Expr::Member(MemberExpr { obj, .. }) => leftmost(obj),
+        Expr::Paren(ParenExpr { expr, .. }) => leftmost(expr),
+        _ => None,
+    }
+}
+
 /// The folder which handles var / function hoisting.
 struct Hoister<'a, 'b> {
     resolver: &'a mut Resolver<'b>,

crates/swc_ecma_transforms_base/tests/ts-resolver/2/input.ts

@@ -0,0 +1,10 @@
+interface Foo {
+    (a: string): void;
+    b: string;
+}
+interface Foo {
+    (a: number): number;
+    c: boolean;
+    d: { x: number; y: number };
+}
+export = Foo;

crates/swc_ecma_transforms_base/tests/ts-resolver/2/output.ts

@@ -0,0 +1,13 @@
+interface Foo__1 {
+    (a: string) : void;
+    b__0: string;
+}
+interface Foo__1 {
+    (a: number) : number;
+    c__0: boolean;
+    d__0: {
+        x__0: number;
+        y__0: number;
+    };
+}
+export = Foo__1