[moshap-firebolt]

try_parse_lambda speculatively parses (<params>) -> <body>. When the body fails, the fallback parses (x) as a nested expression and -> as a binary operator, whose right operand starts the same speculative parse again. A chain of lambdas whose last body is incomplete therefore doubles the work per level:

SELECT (x) -> (x) -> (x) -> ... 1 +

This affects every dialect whose supports_lambda_functions() is true: ClickHouse, Snowflake, DuckDB, Spark and Databricks. On each of them, release build, main 3330dc9e: 20 levels (110 bytes) take 1.4 s, 24 levels (130 bytes) take 23 s. With this change 24 levels take under 0.5 ms and 40 levels about 1 ms.

The fix caches where the lambda arm failed, keyed by position and ParserState as in #2619. Valid SQL never reaches the cache; only a chain that already failed retries it.

Tests: a timeout regression at 24 levels, which fails without the change, and the lambda and -> fallback forms, including a chain whose inner lambda is answered from the cache. Both run on every dialect with supports_lambda_functions().

This PR was prepared with AI assistance (Claude).

Dialects: ClickHouse, Snowflake, DuckDB, Spark, Databricks

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.53%. Comparing base (d9eec6e) to head (451fc78).

Files with missing lines	Patch %	Lines
src/parser/mod.rs	91.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2699   +/-   ##
=======================================
  Coverage   81.53%   81.53%           
=======================================
  Files          42       42           
  Lines       34218    34228   +10     
  Branches    34218    34228   +10     
=======================================
+ Hits        27898    27908   +10     
  Misses       2770     2770           
  Partials     3550     3550           

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