TSQL fix convert function definition (#2843)

* TSQL fix bug where dateparts where sometimes not recognised as such

* Better solution

src/sqlfluff/dialects/dialect_tsql.py

@@ -2004,20 +2004,20 @@ class FunctionSegment(BaseSegment):
             ),
         ),
         Sequence(
+            # https://docs.microsoft.com/en-us/sql/t-sql/functions/cast-and-convert-transact-sql?view=sql-server-ver15
             Ref("ConvertFunctionNameSegment"),
             Bracketed(
-                Delimited(
-                    Ref("DatatypeSegment"),
-                    Ref(
-                        "FunctionContentsGrammar",
-                        # The brackets might be empty for some functions...
-                        optional=True,
-                        ephemeral_name="FunctionContentsGrammar",
-                    ),
-                )
+                Ref("DatatypeSegment"),
+                Bracketed(Ref("NumericLiteralSegment"), optional=True),
+                Ref("CommaSegment"),
+                Ref("ExpressionSegment"),
+                Sequence(
+                    Ref("CommaSegment"), Ref("NumericLiteralSegment"), optional=True
+                ),
             ),
         ),
         Sequence(
+            # https://docs.microsoft.com/en-us/sql/t-sql/functions/cast-and-convert-transact-sql?view=sql-server-ver15
             Ref("CastFunctionNameSegment"),
             Bracketed(
                 Ref("ExpressionSegment"),

test/fixtures/dialects/tsql/create_view.yml

@@ -3,7 +3,7 @@
 # computed by SQLFluff when running the tests. Please run
 # `python test/generate_parse_fixture_yml.py`  to generate them after adding or
 # altering SQL files.
-_hash: 69f2edb341a502903b3fe5048ff31230bf0dc98540a0c9127048de1a7e56332d
+_hash: 68ab90694accab824df1c63fcb2da4a06c8bfe821cbebc61e4a6a6199f2f82fe
 file:
   batch:
   - statement:
@@ -72,8 +72,7 @@ file:
                 - expression:
                     literal: "'20001231'"
                 - comma: ','
-                - expression:
-                    literal: '101'
+                - literal: '101'
                 - end_bracket: )
           groupby_clause:
           - keyword: GROUP
@@ -147,8 +146,7 @@ file:
                 - expression:
                     literal: "'20001231'"
                 - comma: ','
-                - expression:
-                    literal: '101'
+                - literal: '101'
                 - end_bracket: )
           groupby_clause:
           - keyword: GROUP
@@ -232,8 +230,7 @@ file:
                 - expression:
                     literal: "'20010630'"
                 - comma: ','
-                - expression:
-                    literal: '101'
+                - literal: '101'
                 - end_bracket: )
           statement_terminator: ;
   - statement:

test/fixtures/dialects/tsql/date_functions.sql

@@ -0,0 +1,21 @@
+select convert(
+        date, 
+        dateadd(
+            month, 
+            datediff(
+                month, 
+                0, 
+                t.valid_from_date
+            ),
+            0
+        )
+    ) as valid_from_date
+from t as t
+where t.activity_month >= 
+    convert(
+        date, 
+        dateadd(
+            yy, 
+            datediff(yy, 0, getdate()
+        ) - 1, 0)
+    ) 

test/fixtures/dialects/tsql/date_functions.yml

@@ -0,0 +1,116 @@
+# YML test files are auto-generated from SQL files and should not be edited by
+# hand. To help enforce this, the "hash" field in the file must match a hash
+# computed by SQLFluff when running the tests. Please run
+# `python test/generate_parse_fixture_yml.py`  to generate them after adding or
+# altering SQL files.
+_hash: 40f29d7194a7ef8826f20fb21230deceda1301d6e26e7ee6299e08313ca7a65a
+file:
+  batch:
+    statement:
+      select_statement:
+        select_clause:
+          keyword: select
+          select_clause_element:
+            function:
+              function_name:
+                keyword: convert
+              bracketed:
+                start_bracket: (
+                data_type:
+                  identifier: date
+                comma: ','
+                expression:
+                  function:
+                    function_name:
+                      function_name_identifier: dateadd
+                    bracketed:
+                    - start_bracket: (
+                    - date_part: month
+                    - comma: ','
+                    - expression:
+                        function:
+                          function_name:
+                            function_name_identifier: datediff
+                          bracketed:
+                          - start_bracket: (
+                          - date_part: month
+                          - comma: ','
+                          - expression:
+                              literal: '0'
+                          - comma: ','
+                          - expression:
+                              column_reference:
+                              - identifier: t
+                              - dot: .
+                              - identifier: valid_from_date
+                          - end_bracket: )
+                    - comma: ','
+                    - expression:
+                        literal: '0'
+                    - end_bracket: )
+                end_bracket: )
+            alias_expression:
+              keyword: as
+              identifier: valid_from_date
+        from_clause:
+          keyword: from
+          from_expression:
+            from_expression_element:
+              table_expression:
+                table_reference:
+                  identifier: t
+              alias_expression:
+                keyword: as
+                identifier: t
+        where_clause:
+          keyword: where
+          expression:
+            column_reference:
+            - identifier: t
+            - dot: .
+            - identifier: activity_month
+            comparison_operator:
+            - raw_comparison_operator: '>'
+            - raw_comparison_operator: '='
+            function:
+              function_name:
+                keyword: convert
+              bracketed:
+                start_bracket: (
+                data_type:
+                  identifier: date
+                comma: ','
+                expression:
+                  function:
+                    function_name:
+                      function_name_identifier: dateadd
+                    bracketed:
+                    - start_bracket: (
+                    - date_part: yy
+                    - comma: ','
+                    - expression:
+                        function:
+                          function_name:
+                            function_name_identifier: datediff
+                          bracketed:
+                          - start_bracket: (
+                          - date_part: yy
+                          - comma: ','
+                          - expression:
+                              literal: '0'
+                          - comma: ','
+                          - expression:
+                              function:
+                                function_name:
+                                  function_name_identifier: getdate
+                                bracketed:
+                                  start_bracket: (
+                                  end_bracket: )
+                          - end_bracket: )
+                        binary_operator: '-'
+                        literal: '1'
+                    - comma: ','
+                    - expression:
+                        literal: '0'
+                    - end_bracket: )
+                end_bracket: )

test/fixtures/dialects/tsql/functions_a.yml

@@ -3,7 +3,7 @@
 # computed by SQLFluff when running the tests. Please run
 # `python test/generate_parse_fixture_yml.py`  to generate them after adding or
 # altering SQL files.
-_hash: 7fe5e4b983011fd90f3ccda59abb9331f668758dd7ab8a6deecd9ba91864c854
+_hash: b31c58fb4d3cf54ef1b50ffb06ff766a31b0f499ce6240f20b4f6319028e79b6
 file:
 - batch:
     statement:
@@ -108,13 +108,13 @@ file:
               - data_type:
                   identifier: varchar
               - comma: ','
-              - data_type:
-                - identifier: tbl_b
-                - dot: .
-                - identifier: column1
-              - comma: ','
               - expression:
-                  literal: '23'
+                  column_reference:
+                  - identifier: tbl_b
+                  - dot: .
+                  - identifier: column1
+              - comma: ','
+              - literal: '23'
               - end_bracket: )
             alias_expression:
               keyword: AS