Bad diagnostic for error inside closure

[glessard]

Description

A compilation error inside a closure results in a misleading diagnostic.

Reproduction

func example(ptr: UnsafeRawPointer) {
    let regions: [UnsafeRawBufferPointer] = []
    let matchingRegion = regions.first { region in
        let ptr = UInt(bitPattern: ptr)
        return ptr >= UInt(bitPattern: region.baseAddress!)
            && ptr < (UInt(bitPattern: region.baseAddress!) 
                      + UInt(region.bogusProperty))
    } // `bogusProperty` doesn't exist on UnsafeRawBufferPointer
}

See https://swift.godbolt.org/z/oTcq6McaE

The error message is:

<source>:3:34: error: cannot call value of non-function type 'UnsafeRawBufferPointer?'
 1 | func example(ptr: UnsafeRawPointer) {
 2 |     let regions: [UnsafeRawBufferPointer] = []
 3 |     let matchingRegion = regions.first { region in
   |                                  `- error: cannot call value of non-function type 'UnsafeRawBufferPointer?'
 4 |         let ptr = UInt(bitPattern: ptr)
 5 |         return ptr >= UInt(bitPattern: region.baseAddress!)
Compiler returned: 1

Expected behavior

The error should be that bogusProperty isn't a known property of UnsafeRawBufferPointer.

Environment

Swift version 6.2-dev (LLVM 29f45403943bdc7, Swift 299f173)
swift-DEVELOPMENT-SNAPSHOT-2025-08-18-a (actually 6.3-dev)

Additional information

Note that using an inline closure rather than a trailing closure does not help.

same result:

func example(ptr: UnsafeRawPointer) {
    let regions: [UnsafeRawBufferPointer] = []
    let matchingRegion = regions.first(where: { region in
        let ptr = UInt(bitPattern: ptr)
        return ptr >= UInt(bitPattern: region.baseAddress!)
            && ptr < (UInt(bitPattern: region.baseAddress!) 
                      + UInt(region.bogusProperty))
      } // `bogusProperty` doesn't exist on UnsafeRawBufferPointer
    )
}

Credit to Noah Gregory https://swift-open-source.slack.com/archives/C04MRUD6VH8/p1755800748691209