parser: syntax-error for try_cast (#593)

Author: sbdchd

PLAN.md

@@ -704,8 +704,6 @@ name: nullable varchar(255)
 The name of the user in the system.
 ```
 
-- https://r.ena.to/blog/optimizing-postgres-table-layout-for-maximum-efficiency/
-
 rust analyzer gives:
 
 ```
@@ -714,13 +712,21 @@ Error { pub(crate) msg: String, }
 size = 24 (0x18), align = 0x8, needs Drop
 ```
 
-does alignment make sense to have with postgres?
+other fields?
+
+- alignment
+
+  - https://r.ena.to/blog/optimizing-postgres-table-layout-for-maximum-efficiency/
+
+- common values and distribution
+
+  - https://observablehq.com/documentation/cells/data-table#data-table-cell
 
-maybe have common values and distribution somehow?
+- index size on hover
 
-show index size on hover too?
+  - https://www.peterbe.com/plog/index-size-postgresql
 
-- https://www.peterbe.com/plog/index-size-postgresql
+- data staleness -- if you have a daily batch job to calculate data, we could expose the staleness date
 
 #### Table
 

crates/squawk_parser/src/grammar.rs

@@ -1814,6 +1814,7 @@ fn arg_expr(p: &mut Parser<'_>) -> Option<CompletedMarker> {
     p.eat(VARIADIC_KW);
     let r = Restrictions {
         order_by_allowed: true,
+        as_allowed: true,
         ..Restrictions::default()
     };
     expr_bp(p, 1, &r)
@@ -2300,6 +2301,7 @@ fn current_op(p: &Parser<'_>, r: &Restrictions) -> (u8, SyntaxKind, Associativit
         PERCENT if p.next_not_joined_op(0) => (9, PERCENT, Left), // symbol
         // and
         AND_KW if !r.and_disabled => (2, AND_KW, Left),
+        AS_KW if r.as_allowed => (7, AS_KW, Left),
         // /
         SLASH if p.next_not_joined_op(0) => (9, SLASH, Left), // symbol
         // *
@@ -2326,6 +2328,7 @@ const OVERLAPPING_TOKENS: TokenSet = TokenSet::new(&[OR_KW, AND_KW, IS_KW, COLLA
 #[derive(Default)]
 struct Restrictions {
     order_by_allowed: bool,
+    as_allowed: bool,
     in_disabled: bool,
     is_disabled: bool,
     not_disabled: bool,
@@ -2383,7 +2386,7 @@ fn expr_bp(p: &mut Parser<'_>, bp: u8, r: &Restrictions) -> Option<CompletedMark
         let _ = expr_bp(p, op_bp, r);
         lhs = m.complete(
             p,
-            if op == SyntaxKind::COLON_COLON {
+            if matches!(op, COLON_COLON | AS_KW) {
                 CAST_EXPR
             } else if matches!(op, FAT_ARROW | COLON_EQ) {
                 NAMED_ARG

crates/squawk_syntax/src/snapshots/squawk_syntax__test__call_expr_validation.snap

@@ -0,0 +1,31 @@
+---
+source: crates/squawk_syntax/src/test.rs
+input_file: crates/squawk_syntax/test_data/validation/call_expr.sql
+---
+SOURCE_FILE@0..97
+  COMMENT@0..69 "-- Trino/Snowflake/Da ..."
+  WHITESPACE@69..70 "\n"
+  SELECT@70..95
+    SELECT_CLAUSE@70..95
+      SELECT_KW@70..76 "select"
+      WHITESPACE@76..77 " "
+      TARGET_LIST@77..95
+        TARGET@77..95
+          CALL_EXPR@77..95
+            NAME_REF@77..85
+              IDENT@77..85 "try_cast"
+            ARG_LIST@85..95
+              L_PAREN@85..86 "("
+              CAST_EXPR@86..94
+                NAME_REF@86..87
+                  IDENT@86..87 "x"
+                WHITESPACE@87..88 " "
+                AS_KW@88..90 "as"
+                WHITESPACE@90..91 " "
+                NAME_REF@91..94
+                  INT_KW@91..94 "int"
+              R_PAREN@94..95 ")"
+  SEMICOLON@95..96 ";"
+  WHITESPACE@96..97 "\n"
+
+ERROR@86:94 "Invalid cast. Use `cast`, `treat`, or `::` instead."

crates/squawk_syntax/src/validation.rs

@@ -18,6 +18,7 @@ pub(crate) fn validate(root: &SyntaxNode, errors: &mut Vec<SyntaxError>) {
                 ast::PrefixExpr(it) => validate_prefix_expr(it, errors),
                 ast::ArrayExpr(it) => validate_array_expr(it, errors),
                 ast::DropAggregate(it) => validate_drop_aggregate(it, errors),
+                ast::CallExpr(it) => validate_call_expr(it, errors),
                 ast::JoinExpr(it) => validate_join_expr(it, errors),
                 ast::Literal(it) => validate_literal(it, errors),
                 ast::NonStandardParam(it) => validate_non_standard_param(it, errors),
@@ -27,6 +28,20 @@ pub(crate) fn validate(root: &SyntaxNode, errors: &mut Vec<SyntaxError>) {
     }
 }
 
+fn validate_call_expr(it: ast::CallExpr, acc: &mut Vec<SyntaxError>) {
+    let Some(arg_list) = it.arg_list() else {
+        return;
+    };
+    for arg in arg_list.args() {
+        if let ast::Expr::CastExpr(cast_expr) = &arg {
+            acc.push(SyntaxError::new(
+                "Invalid cast. Use `cast`, `treat`, or `::` instead.",
+                cast_expr.syntax().text_range(),
+            ));
+        }
+    }
+}
+
 fn validate_create_table(it: ast::CreateTable, acc: &mut Vec<SyntaxError>) {
     let Some(arg_list) = it.table_arg_list() else {
         return;

crates/squawk_syntax/test_data/validation/call_expr.sql

@@ -0,0 +1,2 @@
+-- Trino/Snowflake/Databricks extension that Postgres doesn't support
+select try_cast(x as int);