lexer: fix unicode escape string issue

crates/squawk_lexer/src/cursor.rs

@@ -33,6 +33,11 @@ impl<'a> Cursor<'a> {
         self.chars.clone().next().unwrap_or(EOF_CHAR)
     }
 
+    /// Peeks the second symbol from the input stream without consuming it.
+    pub(crate) fn second(&self) -> char {
+        self.chars.clone().nth(1).unwrap_or(EOF_CHAR)
+    }
+
     /// Checks if there is nothing more to consume.
     pub(crate) fn is_eof(&self) -> bool {
         self.chars.as_str().is_empty()

crates/squawk_lexer/src/lib.rs

@@ -50,17 +50,17 @@ impl Cursor<'_> {
             c if is_whitespace(c) => self.whitespace(),
 
             // https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-STRINGS-UESCAPE
-            'u' | 'U' => match self.first() {
-                '&' => {
+            'u' | 'U' => {
+                if self.first() == '&' && matches!(self.second(), '\'' | '"') {
                     self.bump();
                     self.prefixed_string(
                         |terminated| LiteralKind::UnicodeEscStr { terminated },
                         true,
                     )
+                } else {
+                    self.ident_or_unknown_prefix()
                 }
-                _ => self.ident_or_unknown_prefix(),
-            },
-
+            }
             // escaped strings
             'e' | 'E' => {
                 self.prefixed_string(|terminated| LiteralKind::EscStr { terminated }, false)
@@ -165,7 +165,7 @@ impl Cursor<'_> {
         // Known prefixes must have been handled earlier. So if
         // we see a prefix here, it is definitely an unknown prefix.
         match self.first() {
-            '#' | '"' | '\'' => TokenKind::UnknownPrefix,
+            '"' | '\'' => TokenKind::UnknownPrefix,
             _ => TokenKind::Ident,
         }
     }

crates/squawk_parser/tests/data/ok/select_operators.sql

@@ -46,6 +46,13 @@ select lseg '[(0,0),(1,1)]' # lseg '[(1,0),(0,1)]';
 -- box intersection
 select box '(2,2),(-1,-1)' # box '(1,1),(-2,-2)';
 
+-- operators that sort of look like prefixes
+select u#foo;
+select u&foo;
+select u& foo;
+select u&&foo;
+select u&$1;
+
 -- closest point
 select point '(0,0)' ## lseg '[(2,0),(0,2)]';
 

crates/squawk_parser/tests/snapshots/tests__select_operators_ok.snap

@@ -483,6 +483,85 @@ SOURCE_FILE
                 STRING "'(1,1),(-2,-2)'"
     SEMICOLON ";"
   WHITESPACE "\n\n"
+  COMMENT "-- operators that sort of look like prefixes"
+  WHITESPACE "\n"
+  SELECT
+    SELECT_CLAUSE
+      SELECT_KW "select"
+      WHITESPACE " "
+      TARGET_LIST
+        TARGET
+          BIN_EXPR
+            NAME_REF
+              IDENT "u"
+            CUSTOM_OP
+              POUND "#"
+            NAME_REF
+              IDENT "foo"
+    SEMICOLON ";"
+  WHITESPACE "\n"
+  SELECT
+    SELECT_CLAUSE
+      SELECT_KW "select"
+      WHITESPACE " "
+      TARGET_LIST
+        TARGET
+          BIN_EXPR
+            NAME_REF
+              IDENT "u"
+            CUSTOM_OP
+              AMP "&"
+            NAME_REF
+              IDENT "foo"
+    SEMICOLON ";"
+  WHITESPACE "\n"
+  SELECT
+    SELECT_CLAUSE
+      SELECT_KW "select"
+      WHITESPACE " "
+      TARGET_LIST
+        TARGET
+          BIN_EXPR
+            NAME_REF
+              IDENT "u"
+            CUSTOM_OP
+              AMP "&"
+            WHITESPACE " "
+            NAME_REF
+              IDENT "foo"
+    SEMICOLON ";"
+  WHITESPACE "\n"
+  SELECT
+    SELECT_CLAUSE
+      SELECT_KW "select"
+      WHITESPACE " "
+      TARGET_LIST
+        TARGET
+          BIN_EXPR
+            NAME_REF
+              IDENT "u"
+            CUSTOM_OP
+              AMP "&"
+              AMP "&"
+            NAME_REF
+              IDENT "foo"
+    SEMICOLON ";"
+  WHITESPACE "\n"
+  SELECT
+    SELECT_CLAUSE
+      SELECT_KW "select"
+      WHITESPACE " "
+      TARGET_LIST
+        TARGET
+          BIN_EXPR
+            NAME_REF
+              IDENT "u"
+            CUSTOM_OP
+              AMP "&"
+            LITERAL
+              POSITIONAL_PARAM "$1"
+    SEMICOLON ";"
+  WHITESPACE "\n\n"
   COMMENT "-- closest point"
   WHITESPACE "\n"
   SELECT