From aa6a7fa775d8f38225ad74a622187bbe891eaf1c Mon Sep 17 00:00:00 2001 From: Matthew Dempsky Date: Thu, 18 Aug 2022 15:16:23 -0700 Subject: [PATCH] cmd/compile: fix reflect naming of local generic types MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit To disambiguate local types, we append a "·N" suffix to their name and then trim it off again when producing their runtime type descriptors. However, if a local type is generic, then we were further appending the type arguments after this suffix, and the code in types/fmt.go responsible for trimming didn't know to handle this. We could extend the types/fmt.go code to look for the "·N" suffix elsewhere in the type name, but this is risky because it could legitimately (albeit unlikely) appear in struct field tags. Instead, the most robust solution is to just change the mangling logic to keep the "·N" suffix at the end, where types/fmt.go can easily and reliably trim it. Note: the "·N" suffix is still visible within the type arguments list (e.g., the "·3" suffixes in nested.out), because we currently use the link strings in the type arguments list. Fixes #54456. Change-Id: Ie9beaf7e5330982f539bff57b8d48868a3674a37 Reviewed-on: https://go-review.googlesource.com/c/go/+/424901 TryBot-Result: Gopher Robot Run-TryBot: Matthew Dempsky Reviewed-by: Cuong Manh Le Reviewed-by: Than McIntosh --- src/cmd/compile/internal/noder/reader.go | 8 ++++- src/cmd/compile/internal/noder/writer.go | 7 +++-- src/cmd/compile/internal/types/fmt.go | 25 +++++++++++----- test/run.go | 1 + test/typeparam/issue54456.go | 37 ++++++++++++++++++++++++ test/typeparam/nested.out | 8 ++--- 6 files changed, 72 insertions(+), 14 deletions(-) create mode 100644 test/typeparam/issue54456.go diff --git a/src/cmd/compile/internal/noder/reader.go b/src/cmd/compile/internal/noder/reader.go index 1acc8c7fb6..5f770166db 100644 --- a/src/cmd/compile/internal/noder/reader.go +++ b/src/cmd/compile/internal/noder/reader.go @@ -777,8 +777,13 @@ func (dict *readerDict) mangle(sym *types.Sym) *types.Sym { return sym } + // If sym is a locally defined generic type, we need the suffix to + // stay at the end after mangling so that types/fmt.go can strip it + // out again when writing the type's runtime descriptor (#54456). + base, suffix := types.SplitVargenSuffix(sym.Name) + var buf strings.Builder - buf.WriteString(sym.Name) + buf.WriteString(base) buf.WriteByte('[') for i, targ := range dict.targs { if i > 0 { @@ -791,6 +796,7 @@ func (dict *readerDict) mangle(sym *types.Sym) *types.Sym { buf.WriteString(targ.LinkString()) } buf.WriteByte(']') + buf.WriteString(suffix) return sym.Pkg.Lookup(buf.String()) } diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go index d9cd1cbd32..c2c3567220 100644 --- a/src/cmd/compile/internal/noder/writer.go +++ b/src/cmd/compile/internal/noder/writer.go @@ -933,8 +933,11 @@ func (w *writer) qualifiedIdent(obj types2.Object) { decl, ok := w.p.typDecls[obj.(*types2.TypeName)] assert(ok) if decl.gen != 0 { - // TODO(mdempsky): Find a better solution than embedding middle - // dot in the symbol name; this is terrible. + // For local defined types, we embed a scope-disambiguation + // number directly into their name. types.SplitVargenSuffix then + // knows to look for this. + // + // TODO(mdempsky): Find a better solution; this is terrible. name = fmt.Sprintf("%s·%v", name, decl.gen) } } diff --git a/src/cmd/compile/internal/types/fmt.go b/src/cmd/compile/internal/types/fmt.go index c1138643b7..c6e99d26c2 100644 --- a/src/cmd/compile/internal/types/fmt.go +++ b/src/cmd/compile/internal/types/fmt.go @@ -340,13 +340,9 @@ func tconv2(b *bytes.Buffer, t *Type, verb rune, mode fmtMode, visited map[*Type // non-fmtTypeID modes. sym := t.Sym() if mode != fmtTypeID { - i := len(sym.Name) - for i > 0 && sym.Name[i-1] >= '0' && sym.Name[i-1] <= '9' { - i-- - } - const dot = "·" - if i >= len(dot) && sym.Name[i-len(dot):i] == dot { - sym = &Sym{Pkg: sym.Pkg, Name: sym.Name[:i-len(dot)]} + base, _ := SplitVargenSuffix(sym.Name) + if len(base) < len(sym.Name) { + sym = &Sym{Pkg: sym.Pkg, Name: base} } } sconv2(b, sym, verb, mode) @@ -704,6 +700,21 @@ func fldconv(b *bytes.Buffer, f *Field, verb rune, mode fmtMode, visited map[*Ty } } +// SplitVargenSuffix returns name split into a base string and a ·N +// suffix, if any. +func SplitVargenSuffix(name string) (base, suffix string) { + i := len(name) + for i > 0 && name[i-1] >= '0' && name[i-1] <= '9' { + i-- + } + const dot = "·" + if i >= len(dot) && name[i-len(dot):i] == dot { + i -= len(dot) + return name[:i], name[i:] + } + return name, "" +} + // Val func FmtConst(v constant.Value, sharp bool) string { diff --git a/test/run.go b/test/run.go index 21f0f7d634..58d09b6b59 100644 --- a/test/run.go +++ b/test/run.go @@ -1990,6 +1990,7 @@ var go118Failures = setOf( "fixedbugs/issue54343.go", // 1.18 compiler assigns receiver parameter to global variable "typeparam/nested.go", // 1.18 compiler doesn't support function-local types with generics "typeparam/issue51521.go", // 1.18 compiler produces bad panic message and link error + "typeparam/issue54456.go", // 1.18 compiler fails to distinguish local generic types "typeparam/issue54497.go", // 1.18 compiler is more conservative about inlining due to repeated issues "typeparam/mdempsky/16.go", // 1.18 compiler uses interface shape type in failed type assertions "typeparam/mdempsky/17.go", // 1.18 compiler mishandles implicit conversions from range loops diff --git a/test/typeparam/issue54456.go b/test/typeparam/issue54456.go new file mode 100644 index 0000000000..8342163e51 --- /dev/null +++ b/test/typeparam/issue54456.go @@ -0,0 +1,37 @@ +// run + +// Copyright 2022 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// The Go 1.18 frontend failed to disambiguate instantiations of +// different, locally defined generic types with the same name. +// +// The unified frontend also exposed the scope-disambiguation mangling +// to end users in reflect data. + +package main + +import ( + "reflect" +) + +func one() any { type T[_ any] int; return T[int](0) } +func two() any { type T[_ any] int; return T[int](0) } + +func main() { + p, q := one(), two() + + // p and q have different dynamic types; this comparison should + // evaluate false. + if p == q { + panic("bad type identity") + } + + for _, x := range []any{p, q} { + // The names here should not contain "·1" or "·2". + if name := reflect.TypeOf(x).String(); name != "main.T[int]" { + panic(name) + } + } +} diff --git a/test/typeparam/nested.out b/test/typeparam/nested.out index 37cb762e32..0836d9b0dc 100644 --- a/test/typeparam/nested.out +++ b/test/typeparam/nested.out @@ -1,4 +1,4 @@ -0,3: main.T·2[int;int] -4,7: main.T·2[int;main.U·3[int;int]] -22,23: main.T·2[main.Int;main.Int] -26,27: main.T·2[main.Int;main.U·3[main.Int;main.Int]] +0,3: main.T[int;int] +4,7: main.T[int;main.U[int;int]·3] +22,23: main.T[main.Int;main.Int] +26,27: main.T[main.Int;main.U[main.Int;main.Int]·3]