Add support to type alias (#205)

*Issue #, if available:*

*Description of changes:*

Please review the PR #175 , #178 , #192 first because of the dependency.

This feature supports the semantics `type ID = string | number`

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choice.

---------

Co-authored-by: ex10si0n <[email protected]>

Author: zhiyuuuu

.gitignore

@@ -9,4 +9,8 @@ Strata.code-workspace
 conformance_testing/__pycache__
 conformance_testing/failures
 
-test_single_file.sh
+test_single_file.sh
+
+node_modules
+package-lock.json
+package.json

Strata/Languages/TypeScript/js_ast.lean

@@ -57,6 +57,10 @@ structure TS_TSTypeAnnotation extends BaseNode where
   typeAnnotation : Option TS_TSTypeKeyword
 deriving Repr, Lean.FromJson, Lean.ToJson
 
+structure TS_TSUnionType extends BaseNode where
+  types : Array TS_TSTypeKeyword
+deriving Repr, Lean.FromJson, Lean.ToJson
+
 structure TS_Identifier extends BaseNode where
   name : String
   typeAnnotation : Option TS_TSTypeAnnotation
@@ -125,6 +129,7 @@ mutual
     | TS_BreakStatement : TS_BreakStatement → TS_Statement
     | TS_SwitchStatement : TS_SwitchStatement → TS_Statement
     | TS_ContinueStatement: TS_ContinueStatement → TS_Statement
+    | TS_TypeAliasDeclaration : TS_TypeAliasDeclaration → TS_Statement
   deriving Repr, Lean.FromJson, Lean.ToJson
 
   inductive TS_AssignmentIdentifier where
@@ -289,6 +294,12 @@ mutual
     discriminant : TS_Expression
     cases : Array TS_SwitchCase
   deriving Repr, Lean.FromJson, Lean.ToJson
+
+    structure TS_TypeAliasDeclaration extends BaseNode where
+    id : TS_Identifier
+    typeAnnotation : TS_TSUnionType
+  deriving Repr, Lean.FromJson, Lean.ToJson
+
 end
 
 instance : Inhabited TS_Expression where

StrataTest/Languages/TypeScript/test_type_alias.ts

@@ -0,0 +1,5 @@
+type ID = string | number;
+
+// Variable declarations using the alias
+let userId: ID = 101;
+let orderId: ID = "ORD_2025";

conformance_testing/babel_to_lean.py

@@ -38,6 +38,8 @@ def parse_ts_type(j):
         return {"TS_TSArrayType": inner}
     elif t == "TSAnyKeyword" or t is None:
         return None
+    elif t == "TSUnionType":
+        return None
     else:
         print("Unsupported type annotation type: " + str(t), file=sys.stderr)
         return None
@@ -334,6 +336,24 @@ def parse_break_statement(j):
     add_missing_node_info(j, target_j)
     return target_j
 
+def parse_type_alias_declaration(j):
+    union_node = j["typeAnnotation"]
+
+    inner_types = union_node.get("types", [])
+    tagged_types = [parse_ts_type(tnode) for tnode in inner_types]
+
+    union_struct = {
+        "types": tagged_types
+    }
+    add_missing_node_info(union_node, union_struct)
+
+    target_j = {
+        "id": parse_identifier(j["id"]),
+        "typeAnnotation": union_struct,
+    }
+    add_missing_node_info(j, target_j)
+    return target_j
+    
 def parse_for_statement(j):
     target_body = parse_statement(j['body'])
     target_j = {
@@ -380,6 +400,8 @@ def parse_statement(j):
         # case "ForInStatement":
         # case "ForOfStatement":
         # case "ClassDeclaration":
+        case "TSTypeAliasDeclaration":
+            return {"TS_TypeAliasDeclaration": parse_type_alias_declaration(j)}
         case _:
             print("Unsupported statement type: " + j['type'], file=sys.stderr)
             return j