cmd/compile: panic in `cmd/compile/internal/types.(*Type).Size` via `cmd/compile/internal/ssa.(*slotCanonicalizer).lookup`

[bcmills]

#!watchflakes
post <- log ~ `internal compiler error: panic: runtime error: invalid memory address or nil pointer dereference` && log ~ `^cmd/compile/internal/types\.\(\*Type\)\.Size`

(pulled out from #57995 (comment))

[bcmills]

Hmm. Not sure why this wasn't matched to #55257, but that issue seems to be overly broad anyway.

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
post <- `internal compiler error: panic: runtime error: invalid memory address or nil pointer dereference` && `^cmd/compile/internal/types\.\(\*Type\)\.Size`

2023-07-25 00:57 darwin-amd64-13 go@6f597a8a runtime [build] (log)

<autogenerated>:1: internal compiler error: panic: runtime error: invalid memory address or nil pointer dereference

goroutine 1 [running]:
runtime/debug.Stack()
	runtime/debug/stack.go:24 +0x5e
cmd/compile/internal/base.FatalfAt({0x2000?, 0x0?}, {0x1968b98, 0x9}, {0xc003f2a850, 0x1, 0x1})
	cmd/compile/internal/base/print.go:230 +0x1d7
cmd/compile/internal/base.Fatalf(...)
	cmd/compile/internal/base/print.go:199
cmd/compile/internal/gc.handlePanic()
...
cmd/compile/internal/gc.compileFunctions.func5({0xc003b5e000, 0xbaf, 0xd50?})
	cmd/compile/internal/gc/compile.go:183 +0x59
cmd/compile/internal/gc.compileFunctions()
	cmd/compile/internal/gc/compile.go:194 +0x1eb
cmd/compile/internal/gc.Main(0x199fbe0)
	cmd/compile/internal/gc/main.go:344 +0x1637
main.main()
	cmd/compile/main.go:57 +0xf9

panic: /tmp/buildlet/go/bin/go build -gcflags  -buildmode=plugin -o /tmp/buildlet/tmp/plugin_test618494740/src/testplugin/plugin-mismatch.so ./plugin-mismatch: exit status 1

2023-07-25 00:57 darwin-amd64-13 go@6f597a8a runtime [build] (log)

<autogenerated>:1: internal compiler error: panic: runtime error: invalid memory address or nil pointer dereference

goroutine 1 [running]:
runtime/debug.Stack()
	runtime/debug/stack.go:24 +0x5e
cmd/compile/internal/base.FatalfAt({0x2000?, 0x0?}, {0x1968b98, 0x9}, {0xc003f2a850, 0x1, 0x1})
	cmd/compile/internal/base/print.go:230 +0x1d7
cmd/compile/internal/base.Fatalf(...)
	cmd/compile/internal/base/print.go:199
cmd/compile/internal/gc.handlePanic()
...
cmd/cgo/internal/testplugin_test.testMain(0xc0000ca000?)
	/tmp/buildlet/go/src/cmd/cgo/internal/testplugin/plugin_test.go:103 +0xb2e fp=0xc0000dbe50 sp=0xc0000db9c8 pc=0x1116bee
cmd/cgo/internal/testplugin_test.TestMain(0xc00003a6f0?)
	/tmp/buildlet/go/src/cmd/cgo/internal/testplugin/plugin_test.go:33 +0x76 fp=0xc0000dbe88 sp=0xc0000dbe50 pc=0x1115f96
main.main()
	_testmain.go:91 +0x1c6 fp=0xc0000dbf40 sp=0xc0000dbe88 pc=0x111a746
runtime.main()
	/tmp/buildlet/go/src/runtime/proc.go:267 +0x2bb fp=0xc0000dbfe0 sp=0xc0000dbf40 pc=0x10382bb
runtime.goexit()
	/tmp/buildlet/go/src/runtime/asm_amd64.s:1650 +0x1 fp=0xc0000dbfe8 sp=0xc0000dbfe0 pc=0x1069da1

— watchflakes

[mknyszek]

This looks like it's probably some runtime bug or memory corruption.

[bcmills]

Given darwin/amd64, possibly #60449?