From 79e92c3b41164475ae63aae3b357ce903685227c Mon Sep 17 00:00:00 2001
From: geooo109 <geomichas96@gmail.com>
Date: Thu, 19 Dec 2024 18:35:12 +0200
Subject: [PATCH] PR Feedback 1

---
 sqlglot/dialects/tsql.py    | 11 ++++++-----
 tests/dialects/test_tsql.py | 20 ++++++++++++++------
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/sqlglot/dialects/tsql.py b/sqlglot/dialects/tsql.py
index b17c667b4a..7aa7a0e22b 100644
--- a/sqlglot/dialects/tsql.py
+++ b/sqlglot/dialects/tsql.py
@@ -370,14 +370,14 @@ def _timestrtotime_sql(self: TSQL.Generator, expression: exp.TimeStrToTime):
     return sql
 
 
-def _parse_datetrunc(args: t.List) -> exp.TimestampTrunc:
+def _build_datetrunc(args: t.List) -> exp.TimestampTrunc:
     unit = seq_get(args, 0)
     this = seq_get(args, 1)
 
-    if isinstance(this, exp.Expression) and this.is_string:
-        this = exp.TimeStrToTime(this=this)
+    if this and this.is_string:
+        this = exp.cast(this, exp.DataType.Type.DATETIME2)
 
-    return exp.TimestampTrunc(unit=unit, this=this)
+    return exp.TimestampTrunc(this=this, unit=unit)
 
 
 class TSQL(Dialect):
@@ -580,7 +580,7 @@ class Parser(parser.Parser):
             "SUSER_SNAME": exp.CurrentUser.from_arg_list,
             "SYSTEM_USER": exp.CurrentUser.from_arg_list,
             "TIMEFROMPARTS": _build_timefromparts,
-            "DATETRUNC": _parse_datetrunc,
+            "DATETRUNC": _build_datetrunc,
         }
 
         JOIN_HINTS = {"LOOP", "HASH", "MERGE", "REMOTE"}
@@ -947,6 +947,7 @@ class Generator(generator.Generator):
             exp.Trim: trim_sql,
             exp.TsOrDsAdd: date_delta_sql("DATEADD", cast=True),
             exp.TsOrDsDiff: date_delta_sql("DATEDIFF"),
+            exp.TimestampTrunc: lambda self, e: self.func("DATETRUNC", e.unit, e.this),
         }
 
         TRANSFORMS.pop(exp.ReturnsProperty)
diff --git a/tests/dialects/test_tsql.py b/tests/dialects/test_tsql.py
index b0ead2f52a..4c61780d76 100644
--- a/tests/dialects/test_tsql.py
+++ b/tests/dialects/test_tsql.py
@@ -2091,18 +2091,26 @@ def test_next_value_for(self):
             },
         )
 
+    # string literals in the DATETRUNC are casted as DATETIME2
     def test_datetrunc(self):
         self.validate_all(
-            "SELECT DATETRUNC(month, '2021-12-08 11:30:15.1234567')",
+            "SELECT DATETRUNC(month, 'foo')",
             write={
-                "duckdb": "SELECT DATE_TRUNC('MONTH', CAST('2021-12-08 11:30:15.1234567' AS TIMESTAMP))"
+                "duckdb": "SELECT DATE_TRUNC('MONTH', CAST('foo' AS TIMESTAMP))",
+                "tsql": "SELECT DATETRUNC(MONTH, CAST('foo' AS DATETIME2))",
             },
         )
         self.validate_all(
-            "SELECT DATETRUNC(year, DATEFROMPARTS(2010, 12, 31))",
-            write={"duckdb": "SELECT DATE_TRUNC('YEAR', MAKE_DATE(2010, 12, 31))"},
+            "SELECT DATETRUNC(month, foo)",
+            write={
+                "duckdb": "SELECT DATE_TRUNC('MONTH', foo)",
+                "tsql": "SELECT DATETRUNC(MONTH, foo)",
+            },
         )
         self.validate_all(
-            "SELECT DATETRUNC(year, CAST('2021-12-08' AS date))",
-            write={"duckdb": "SELECT DATE_TRUNC('YEAR', CAST('2021-12-08' AS DATE))"},
+            "SELECT DATETRUNC(year, CAST('foo1' AS date))",
+            write={
+                "duckdb": "SELECT DATE_TRUNC('YEAR', CAST('foo1' AS DATE))",
+                "tsql": "SELECT DATETRUNC(YEAR, CAST('foo1' AS DATE))",
+            },
         )