Fix CAST parsing to handle expression type arguments like 'Str'||'ing'

When parsing CAST(x, type) with comma syntax, check if the type string
is followed by an operator (CONCAT, PLUS, MINUS) before consuming it.
If so, parse it as a full expression to handle cases like:
  CAST(123, 'Str'||'ing')

Fixes 03011_definitive_guide_to_cast/stmt36.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

parser/expression.go

@@ -1557,7 +1557,9 @@ func (p *Parser) parseCast() ast.Expression {
 		p.nextToken()
 		// Type can be given as a string literal or an expression (e.g., if(cond, 'Type1', 'Type2'))
 		// It can also have an alias like: cast('1234', 'UInt32' AS rhs)
-		if p.currentIs(token.STRING) {
+		// For expressions like 'Str'||'ing', we need to parse the full expression
+		if p.currentIs(token.STRING) && !p.peekIs(token.CONCAT) && !p.peekIs(token.PLUS) && !p.peekIs(token.MINUS) {
+			// Simple string literal type, not part of an expression
 			typeStr := p.current.Value
 			typePos := p.current.Pos
 			p.nextToken()
@@ -1597,7 +1599,7 @@ func (p *Parser) parseCast() ast.Expression {
 				expr.Type = &ast.DataType{Position: typePos, Name: typeStr}
 			}
 		} else {
-			// Parse as expression for dynamic type casting
+			// Parse as expression for dynamic type casting or expressions like 'Str'||'ing'
 			expr.TypeExpr = p.parseExpression(LOWEST)
 		}
 	}

parser/testdata/03011_definitive_guide_to_cast/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt36": true
-  }
-}
+{}