[WIP] Add CanImportExpr node

Author: StevenWong12

CodeGeneration/Sources/SyntaxSupport/ExprNodes.swift

@@ -184,6 +184,41 @@ public let EXPR_NODES: [Node] = [
       ),
     ]
   ),
+  
+  // the canImport expr in if config expression
+  Node(
+    name: "CanImportExpr",
+    nameForDiagnostics: "'canImport' expression in if config expression",
+    kind: "Expr",
+    children: [
+      Child(
+        name: "CanImportKeyword",
+        kind: .token(choices: [.token(tokenKind: "IdentifierToken")])
+      ),
+      Child(
+        name: "LeftParen",
+        kind: .token(choices: [.token(tokenKind: "LeftParenToken")])
+      ),
+      Child(
+        name: "ImportPath",
+        kind: .token(choices: [.token(tokenKind: "IdentifierToken")])
+      ),
+      Child(
+        name: "Comma",
+        kind: .token(choices: [.token(tokenKind: "CommaToken")]),
+        isOptional: true
+      ),
+      Child(
+        name: "Version",
+        kind: .node(kind: "TupleExprElement"),
+        isOptional: true
+      ),
+      Child(
+        name: "RightParen",
+        kind: .token(choices: [.token(tokenKind: "RightParenToken")])
+      )
+    ]
+  ),
 
   // case-item -> pattern where-clause? ','?
   Node(