[RELAY] Fix function call parsing for binary op (#2424)

python/tvm/relay/grammar/Relay.g4

@@ -53,14 +53,15 @@ prog: (defn* | expr) EOF ;
 expr
   // operators
   : '(' expr ')'                              # parens
+  // function application
+  | expr '(' (expr (',' expr)*)? ')'          # call
   | '-' expr                                  # neg
   | expr op=('*'|'/') expr                    # binOp
   | expr op=('+'|'-') expr                    # binOp
   | expr op=('<'|'>'|'<='|'>=') expr          # binOp
   | expr op=('=='|'!=') expr                  # binOp
 
-  // function definition and application
-  | expr '(' (expr (',' expr)*)? ')'          # call
+  // function definition
   | func                                      # funcExpr
 
   // tuples and tensors

tests/python/relay/test_ir_parser.py

@@ -316,6 +316,22 @@ def test_ifelse_scope():
 
 @if_parser_enabled
 def test_call():
+    # select right function to call: simple ident case
+    id_func = relay.Var("id")
+    assert alpha_equal(
+        relay.fromtext(
+        """
+        let %id = fn (%x) { %x };
+        10 * %id(10)
+        """
+        ),
+        relay.Let(
+            id_func,
+            relay.Function([X], X, None, []),
+            relay.multiply(relay.const(10), relay.Call(id_func, [relay.const(10)]))
+        )
+    )
+
     # 0 args
     constant = relay.Var("constant")
     assert alpha_equal(