lambda type coercion [Test - Do Not Review]

[Dilli-Babu-Godari]

Description

Motivation and Context

Impact

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[sourcery-ai]

Reviewer's Guide

Enhance lambda handling to support return type coercion during SQL function analysis: introduce exception handling for invalid lambda argument counts, normalize dependent function signature arguments, apply coercion to lambda return types when actual and expected types differ but are coercible, update the signature binder to allow coercion, and add corresponding tests for array_sort lambdas.

Class diagram for updated lambda handling in ExpressionAnalyzer

classDiagram
class ExpressionAnalyzer {
  +analyze(expression, baseScope, context)
  +process(expression, context)
  +addOrReplaceExpressionCoercion(expression, fromType, toType)
  +setExpressionType(expression, type)
}
class LambdaArgumentCountMismatchException {
  +LambdaArgumentCountMismatchException(Node node, String message)
}
ExpressionAnalyzer --> LambdaArgumentCountMismatchException : throws

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Class diagram for SignatureBinder update to allow lambda return type coercion

classDiagram
class SignatureBinder {
  +update(BoundVariables.Builder bindings)
  -appendTypeRelationshipConstraintSolver(..., allowCoercion)
  -appendConstraintSolvers(..., allowCoercion)
}
SignatureBinder --> "TypeConstraintSolver"

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File-Level Changes

Change	Details	Files
Catch invalid lambda argument counts and return UNKNOWN signature	Introduce LambdaArgumentCountMismatchException extending SemanticException Wrap inner ExpressionAnalyzer setup/analyze block for lambdas in try/catch Return UNKNOWN type signature when mismatch exception is thrown	presto-main-base/src/main/java/com/facebook/presto/sql/analyzer/ExpressionAnalyzer.java
Add coercion logic for lambda return types in ExpressionAnalyzer	After processing a lambda expression, detect if actual return type differs from expected Verify if actual type can be coerced to expected and, if so, add or replace expression coercion on the lambda body Update the expression’s inferred type to the expected function type	presto-main-base/src/main/java/com/facebook/presto/sql/analyzer/ExpressionAnalyzer.java
Normalize function signature arguments to handle lambda dependencies	Build a normalized argument list in resolveFunction Treat null or dependent TypeSignatureProviders as UNKNOWN to prevent resolution errors	presto-main-base/src/main/java/com/facebook/presto/sql/analyzer/ExpressionAnalyzer.java
Allow coercion for lambda return types in SignatureBinder	Change appendTypeRelationshipConstraintSolver call to pass allowCoercion flag instead of always false	presto-main-base/src/main/java/com/facebook/presto/metadata/SignatureBinder.java
Add array_sort lambda return type coercion tests	Implement testArraySortLambdaReturnTypeCoercion with multiple assertFunction scenarios covering numeric, string, null, and mixed-type cases	presto-main-base/src/test/java/com/facebook/presto/type/TestArrayOperators.java

Possibly linked issues

• Don't contact metastore when reading data #123: The PR fixes the array_sort function by handling lambda argument count mismatches and enabling type coercion for lambda return types, allowing 2-argument comparators to work.

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The committers listed above are authorized under a signed CLA.

• ✅ login: Dilli-Babu-Godari / name: Dilli-Babu-Godari (b20a0ba)