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mateusz834 opened this issue Feb 22, 2025 · 3 comments
Open

x/tools/go/ssa: panic in emitConv in InstantiateGenerics mode #71899

mateusz834 opened this issue Feb 22, 2025 · 3 comments
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BugReport Issues describing a possible bug in the Go implementation. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Tools This label describes issues relating to any tools in the x/tools repository.
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Unreleased

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@mateusz834
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const hello = `package aa

import "fmt"

func foo[A fmt.Stringer]() int {
	a := make([]A, 128)
	a[1].String()
	return len(a)
}

func bar() {
	foo[fmt.Stringer]()
}
`

func main() {
	// Parse the source files.
	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, "hello.go", hello, parser.ParseComments|parser.SkipObjectResolution)
	if err != nil {
		fmt.Print(err) // parse error
		return
	}
	files := []*ast.File{f}
	// Create the type-checker's package.
	pkg := types.NewPackage("hello", "")

	// Type-check the package, load dependencies.
	// Create and build the SSA program.
	_, _, err = ssautil.BuildPackage(
		&types.Config{Importer: importer.Default()}, fset, pkg, files, ssa.SanityCheckFunctions|ssa.GlobalDebug|ssa.LogSource|ssa.InstantiateGenerics)
	if err != nil {
		fmt.Print(err) // type error in some package
		return
	}
}
$ go run .
build package hello
build hello.init @ -
build hello.init @ - end
build hello.foo @ hello.go:5:6
build hello.foo @ hello.go:5:6 end
build hello.bar @ hello.go:11:6
build hello.bar @ hello.go:11:6 end
build hello.foo[fmt.Stringer] @ hello.go:5:6
build hello.foo[fmt.Stringer] @ hello.go:5:6 end
build package hello end
panic: in hello.foo[fmt.Stringer]: cannot convert term slice t0[:128:int] ([]fmt.Stringer [within []fmt.Stringer]) to type []fmt.Stringer [within []fmt.Stringer]

goroutine 1 [running]:
golang.org/x/tools/go/ssa.emitConv.func1({0x726cd8, 0xc000244d60}, {0x726cd8, 0xc000244d40})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/emit.go:311 +0x339
golang.org/x/tools/go/ssa.emitConv.func2.1({0x726cd8?, 0xc000244d40?})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/emit.go:320 +0x4c
golang.org/x/tools/go/ssa.underIs.func1({0xc0001ef448?, 0x2?}, {0x726cd8?, 0xc000244d40?})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/typeset.go:100 +0x34
golang.org/x/tools/go/ssa.typeset({0x726cd8?, 0xc000244d40?}, 0xc0001ef4a0)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/typeset.go:45 +0x103
golang.org/x/tools/go/ssa.underIs({0x726cd8?, 0xc000244d40?}, 0xc0001ef530?)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/typeset.go:99 +0x45
golang.org/x/tools/go/ssa.emitConv.func2({0x726cd8?, 0xc000244d60?})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/emit.go:318 +0x58
golang.org/x/tools/go/ssa.underIs.func1({0xc0001b3f80?, 0x10?}, {0x726cd8?, 0xc000244d60?})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/typeset.go:100 +0x34
golang.org/x/tools/go/ssa.typeset({0x726cd8?, 0xc000244d60?}, 0xc0001ef5c0)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/typeset.go:45 +0x103
golang.org/x/tools/go/ssa.underIs({0x726cd8?, 0xc000244d60?}, 0xc000244d60?)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/typeset.go:99 +0x45
golang.org/x/tools/go/ssa.emitConv(0xc000272e00, {0x7dd9cca91f90, 0xc0001d9300}, {0x726cd8, 0xc000244d40})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/emit.go:317 +0x67b
golang.org/x/tools/go/ssa.emitStore(0xc000272e00, {0x729c18, 0xc000232fc0}, {0x7dd9cca91f90, 0xc0001d9300}, 0x3d)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/emit.go:418 +0x58
golang.org/x/tools/go/ssa.(*address).store(0xc0002418c0, 0xc000272e00, {0x7dd9cca91f90?, 0xc0001d9300?})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/lvalue.go:42 +0x45
golang.org/x/tools/go/ssa.(*storebuf).emit(...)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:543
golang.org/x/tools/go/ssa.(*builder).assignStmt(0xc0002407e0, 0xc000272e00, {0xc0000141c0, 0x1, 0x3?}, {0xc0000141e0, 0x1, 0xc000241f80?}, 0x1)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:1223 +0x41c
golang.org/x/tools/go/ssa.(*builder).stmt(0xc0002407e0, 0xc000272e00, {0x727880?, 0xc00010e500?})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:2712 +0xd13
golang.org/x/tools/go/ssa.(*builder).stmtList(...)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:964
golang.org/x/tools/go/ssa.(*builder).stmt(0xc0002407e0, 0xc000272e00, {0x727790?, 0xc00007e8a0?})
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:2745 +0x1046
golang.org/x/tools/go/ssa.(*builder).buildFromSyntax(0xc0002407e0, 0xc000272e00)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:2951 +0x265
golang.org/x/tools/go/ssa.(*builder).buildFunction(0xc0002407e0?, 0xc000272e00)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:2904 +0x186
golang.org/x/tools/go/ssa.(*builder).iterate(0xc0002407e0)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:2889 +0x25
golang.org/x/tools/go/ssa.(*Package).build(0xc0001d8b80)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:3172 +0xce
sync.(*Once).doSlow(0xc000234e10?, 0xc000032720?)
        /usr/lib/go/src/sync/once.go:76 +0xb4
sync.(*Once).Do(...)
        /usr/lib/go/src/sync/once.go:67
golang.org/x/tools/go/ssa.(*Package).Build(...)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/builder.go:3161
golang.org/x/tools/go/ssa/ssautil.BuildPackage(0xc0001308c0, 0xc00010e3c0, 0xc000032720, {0xc0000580b0, 0x1, 0x1}, 0x14c)
        /home/mateusz/go/pkg/mod/golang.org/x/tools@v0.30.0/go/ssa/ssautil/load.go:187 +0x475
main.main()
        /tmp/cc/main.go:44 +0x17c
exit status 2

This happens only when ssa.InstantiateGenerics is passed to BuildPackage.

CC @adonovan @timothy-king per https://dev.golang.org/owners
@gopherbot gopherbot added the Tools This label describes issues relating to any tools in the x/tools repository. label Feb 22, 2025
@gopherbot gopherbot added this to the Unreleased milestone Feb 22, 2025
@gabyhelp
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Related Issues

(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)

@gabyhelp gabyhelp added the BugReport Issues describing a possible bug in the Go implementation. label Feb 22, 2025
@prattmic
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cc @timothy-king @adonovan

@prattmic prattmic added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Feb 24, 2025
@adonovan
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adonovan commented Feb 25, 2025 •
edited
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Thanks for the test case, it reproduces the problem for me (even though, curiously, go run ./cmd/ssadump -build=DCGFL hello.go does not). I can further reduce the test input to this:

package aa

import "fmt"

func foo[A fmt.Stringer]() any {
	a := make([]A, 1)
	return a
}

var _ = foo[fmt.Stringer]()

but declaring Stringer instead of importing it causes the test to pass, suggesting that the importer is involved.

Adding some logging to emitConv after the failed IsIdentical, it appears that the two operands representing []fmt.Stringer have different Named types and different TypeName objects, even after applying Origin:

	log.Println(typ, t_src, ut_dst, ut_src)
	if fmt.Sprint(t_src) == "[]fmt.Stringer" {
		log.Printf("%p %p",
			ut_dst.(*types.Slice).Elem().(*types.Named).Origin().Obj(),
			ut_src.(*types.Slice).Elem().(*types.Named).Origin().Obj())
	}

2025/02/25 12:46:08 []fmt.Stringer []fmt.Stringer []fmt.Stringer []fmt.Stringer
2025/02/25 12:46:08 0x140000e1a90 0x140000e1e50

So I think this is some kind of canonicalization bug in importer.Default().

If feasible, you may find that using ssautil.Packages (+ call to Build) is a better tested and more reliable path.

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@prattmic @adonovan @gopherbot @mateusz834 @gabyhelp