Fix "Compiler crashes when illegal signature of applyDynamic is used "

[lihaoyi]

Attempts to fix #24037. Vibe coded

Claude's explanation

Root Cause: The isStructuralTermSelectOrApply function in TreeInfo.scala was treating calls to dynamic methods (selectDynamic, applyDynamic, etc.) as structural calls when the symbol lookup failed. This caused handleStructural to be called recursively, creating an infinite loop.

Fix: Added a guard in isStructuralTermSelectOrApply to exclude calls where the method name is one of the dynamic method names (applyDynamic, selectDynamic, updateDynamic, applyDynamicNamed). This prevents treating already-handled dynamic method calls as structural calls, breaking the infinite recursion.

Changes Made

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala:
def isDynamicMethod(name: Name): Boolean =
name == nme.applyDynamic || name == nme.selectDynamic ||
name == nme.updateDynamic || name == nme.applyDynamicNamed

// Added check: && !isDynamicMethod(tree.name)

tests/neg/i24037.scala (new test file):

• Test case 1: Original issue - illegal applyDynamic signature with only one parameter list
• Test case 2: Method call with illegal applyDynamic
• Test case 3: Wrong return type on selectDynamic

[lihaoyi]

This should be ready for review I think