[dev.typeparams] all: merge master (785a8f6) into dev.typeparams

- test/run.go

  CL 328050 added fixedbugs/issue46749.go to -G=3 excluded files list

Merge List:

+ 2021-06-16 785a8f677f cmd/compile: better error message for invalid untyped operation
+ 2021-06-16 a752bc0746 syscall: fix TestGroupCleanupUserNamespace test failure on Fedora
+ 2021-06-15 d77f4c0c5c net/http: improve some server docs
+ 2021-06-15 219fe9d547 cmd/go: ignore UTF8 BOM when reading source code
+ 2021-06-15 723f199edd cmd/link: set correct flags in .dynamic for PIE buildmode
+ 2021-06-15 4d2d89ff42 cmd/go, go/build: update docs to use //go:build syntax
+ 2021-06-15 033d885315 doc/go1.17: document go run pkg@version
+ 2021-06-15 ea8612ef42 syscall: disable c-shared test when no cgo, for windows/arm
+ 2021-06-15 abc56fd1a0 internal/bytealg: remove duplicate go:build line
+ 2021-06-15 4061d3463b syscall: rewrite handle inheritance test to use C rather than Powershell
+ 2021-06-15 cf4e3e3d3b reflect: explain why convertible or comparable types may still panic
+ 2021-06-14 7841cb14d9 doc/go1.17: assorted fixes
+ 2021-06-14 8a5a6f46dc debug/elf: don't apply DWARF relocations for ET_EXEC binaries
+ 2021-06-14 9d13f8d43e runtime: update the variable name in comment
+ 2021-06-14 0fd20ed5b6 reflect: use same conversion panic in reflect and runtime
+ 2021-06-14 6bbb0a9d4a cmd/internal/sys: mark windows/arm64 as c-shared-capable
+ 2021-06-14 d4f34f8c63 doc/go1.17: reword "results" in stack trace printing

Change-Id: I60d1f67c4d48cd4093c350fc89bd60c454d23944

doc/go1.17.html

@@ -59,7 +59,7 @@ Do not send CLs removing the interior tags from such phrases.
 </ul>
 
 <p>
-  These enhancements were added to simplify writing code that conforms
+  The package unsafe enhancements were added to simplify writing code that conforms
   to <code>unsafe.Pointer</code>'s <a href="/pkg/unsafe/#Pointer">safety
   rules</a>, but the rules remain unchanged. In particular, existing
   programs that correctly use <code>unsafe.Pointer</code> remain
@@ -292,6 +292,18 @@ Do not send CLs removing the interior tags from such phrases.
   <a href="https://golang.org/design/draft-gobuild">https://golang.org/design/draft-gobuild</a>.
 </p>
 
+<h4 id="go run"><code>go</code> <code>run</code></h4>
+
+<p><!-- golang.org/issue/42088 -->
+  <code>go</code> <code>run</code> now accepts arguments with version suffixes
+  (for example, <code>go</code> <code>run</code>
+  <code>example.com/cmd@v1.0.0</code>).  This causes <code>go</code>
+  <code>run</code> to build and run packages in module-aware mode, ignoring the
+  <code>go.mod</code> file in the current directory or any parent directory, if
+  there is one. This is useful for running executables without installing them or
+  without changing dependencies of the current module.
+</p>
+
 <h3 id="gofmt">Gofmt</h3>
 
 <p>
@@ -406,7 +418,8 @@ func Foo() bool {
   by commas. Aggregate-typed (struct, array, string, slice, interface, and complex)
   arguments are delimited by curly braces. A caveat is that the value of an
   argument that only lives in a register and is not stored to memory may be
-  inaccurate. Results (which were usually inaccurate) are no longer printed.
+  inaccurate. Function return values (which were usually inaccurate) are no longer
+  printed.
 </p>
 
 <p><!-- CL 283112, golang.org/issue/28727 -->
@@ -734,7 +747,7 @@ func Foo() bool {
       These components were always interpreted as decimal, but some operating systems treat them as octal.
       This mismatch could hypothetically lead to security issues if a Go application was used to validate IP addresses
       which were then used in their original form with non-Go applications which interpreted components as octal. Generally,
-      it is advisable to always re-encoded values after validation, which avoids this class of parser misalignment issues.
+      it is advisable to always re-encode values after validation, which avoids this class of parser misalignment issues.
     </p>
   </dd>
 </dl><!-- net -->
@@ -785,7 +798,7 @@ func Foo() bool {
   <dd>
     <p><!-- CL 268020 -->
       The <a href="/pkg/os/#File.WriteString"><code>File.WriteString</code></a> method
-      has been optimized to no longer make a copy of the input string.
+      has been optimized to not make a copy of the input string.
     </p>
   </dd>
 </dl><!-- os -->
@@ -811,6 +824,14 @@ func Foo() bool {
       The <a href="/pkg/reflect/#ArrayOf"><code>ArrayOf</code></a> function now panics when
       called with a negative length.
     </p>
+
+    <p><!-- CL 301652 -->
+      Checking the <a href="/pkg/reflect/#Type"><code>Type.ConvertibleTo</code></a> method
+      is no longer sufficient to guarantee that a call to
+      <a href="/pkg/reflect/#Value.Convert"><code>Value.Convert</code></a> will not panic.
+      It may panic when converting `[]T` to `*[N]T` if the slice's length is less than N.
+      See the language changes section above.
+    </p>
   </dd>
 </dl><!-- reflect -->
 
@@ -837,7 +858,7 @@ func Foo() bool {
   <dd>
     <p><!-- CL 170079, CL 170080 -->
       The <code>strconv</code> package now uses Ulf Adams's Ryū algorithm for formatting floating-point numbers.
-      This algorithm improves performance on most inputs, and is more than 99% faster on worst-case inputs.
+      This algorithm improves performance on most inputs and is more than 99% faster on worst-case inputs.
     </p>
 
     <p><!-- CL 314775 -->

src/cmd/compile/internal/typecheck/const.go

@@ -633,6 +633,17 @@ func defaultlit2(l ir.Node, r ir.Node, force bool) (ir.Node, ir.Node) {
 	if l.Type() == nil || r.Type() == nil {
 		return l, r
 	}
+
+	if !l.Type().IsInterface() && !r.Type().IsInterface() {
+		// Can't mix bool with non-bool, string with non-string.
+		if l.Type().IsBoolean() != r.Type().IsBoolean() {
+			return l, r
+		}
+		if l.Type().IsString() != r.Type().IsString() {
+			return l, r
+		}
+	}
+
 	if !l.Type().IsUntyped() {
 		r = convlit(r, l.Type())
 		return l, r
@@ -647,17 +658,10 @@ func defaultlit2(l ir.Node, r ir.Node, force bool) (ir.Node, ir.Node) {
 		return l, r
 	}
 
-	// Can't mix bool with non-bool, string with non-string, or nil with anything (untyped).
-	if l.Type().IsBoolean() != r.Type().IsBoolean() {
-		return l, r
-	}
-	if l.Type().IsString() != r.Type().IsString() {
-		return l, r
-	}
+	// Can't mix nil with anything untyped.
 	if ir.IsNil(l) || ir.IsNil(r) {
 		return l, r
 	}
-
 	t := defaultType(mixUntyped(l.Type(), r.Type()))
 	l = convlit(l, t)
 	r = convlit(r, t)

src/cmd/dist/test.go

@@ -1057,7 +1057,7 @@ func (t *tester) supportedBuildmode(mode string) bool {
 			"darwin-amd64", "darwin-arm64",
 			"freebsd-amd64",
 			"android-arm", "android-arm64", "android-386",
-			"windows-amd64", "windows-386":
+			"windows-amd64", "windows-386", "windows-arm64":
 			return true
 		}
 		return false

src/cmd/go/alldocs.go

@@ -1568,7 +1568,7 @@
 //
 // A build constraint, also known as a build tag, is a line comment that begins
 //
-// 	// +build
+// 	//go:build
 //
 // that lists the conditions under which a file should be included in the package.
 // Constraints may appear in any kind of source file (not just Go), but
@@ -1576,30 +1576,20 @@
 // only by blank lines and other line comments. These rules mean that in Go
 // files a build constraint must appear before the package clause.
 //
-// To distinguish build constraints from package documentation, a series of
-// build constraints must be followed by a blank line.
+// To distinguish build constraints from package documentation,
+// a build constraint should be followed by a blank line.
 //
-// A build constraint is evaluated as the OR of space-separated options.
-// Each option evaluates as the AND of its comma-separated terms.
-// Each term consists of letters, digits, underscores, and dots.
-// A term may be negated with a preceding !.
-// For example, the build constraint:
+// A build constraint is evaluated as an expression containing options
+// combined by ||, &&, and ! operators and parentheses. Operators have
+// the same meaning as in Go.
 //
-// 	// +build linux,386 darwin,!cgo
+// For example, the following build constraint constrains a file to
+// build when the "linux" and "386" constraints are satisfied, or when
+// "darwin" is satisfied and "cgo" is not:
 //
-// corresponds to the boolean formula:
+// 	//go:build (linux && 386) || (darwin && !cgo)
 //
-// 	(linux AND 386) OR (darwin AND (NOT cgo))
-//
-// A file may have multiple build constraints. The overall constraint is the AND
-// of the individual constraints. That is, the build constraints:
-//
-// 	// +build linux darwin
-// 	// +build amd64
-//
-// corresponds to the boolean formula:
-//
-// 	(linux OR darwin) AND amd64
+// It is an error for a file to have more than one //go:build line.
 //
 // During a particular build, the following words are satisfied:
 //
@@ -1637,24 +1627,28 @@
 //
 // To keep a file from being considered for the build:
 //
-// 	// +build ignore
+// 	//go:build ignore
 //
 // (any other unsatisfied word will work as well, but "ignore" is conventional.)
 //
 // To build a file only when using cgo, and only on Linux and OS X:
 //
-// 	// +build linux,cgo darwin,cgo
+// 	//go:build cgo && (linux || darwin)
 //
 // Such a file is usually paired with another file implementing the
 // default functionality for other systems, which in this case would
 // carry the constraint:
 //
-// 	// +build !linux,!darwin !cgo
+// 	//go:build !(cgo && (linux || darwin))
 //
 // Naming a file dns_windows.go will cause it to be included only when
 // building the package for Windows; similarly, math_386.s will be included
 // only when building the package for 32-bit x86.
 //
+// Go versions 1.16 and earlier used a different syntax for build constraints,
+// with a "// +build" prefix. The gofmt command will add an equivalent //go:build
+// constraint when encountering the older syntax.
+//
 //
 // Build modes
 //

src/cmd/go/internal/help/helpdoc.go

@@ -784,7 +784,7 @@ var HelpBuildConstraint = &base.Command{
 	Long: `
 A build constraint, also known as a build tag, is a line comment that begins
 
-	// +build
+	//go:build
 
 that lists the conditions under which a file should be included in the package.
 Constraints may appear in any kind of source file (not just Go), but
@@ -792,30 +792,20 @@ they must appear near the top of the file, preceded
 only by blank lines and other line comments. These rules mean that in Go
 files a build constraint must appear before the package clause.
 
-To distinguish build constraints from package documentation, a series of
-build constraints must be followed by a blank line.
+To distinguish build constraints from package documentation,
+a build constraint should be followed by a blank line.
 
-A build constraint is evaluated as the OR of space-separated options.
-Each option evaluates as the AND of its comma-separated terms.
-Each term consists of letters, digits, underscores, and dots.
-A term may be negated with a preceding !.
-For example, the build constraint:
+A build constraint is evaluated as an expression containing options
+combined by ||, &&, and ! operators and parentheses. Operators have
+the same meaning as in Go.
 
-	// +build linux,386 darwin,!cgo
+For example, the following build constraint constrains a file to
+build when the "linux" and "386" constraints are satisfied, or when
+"darwin" is satisfied and "cgo" is not:
 
-corresponds to the boolean formula:
+	//go:build (linux && 386) || (darwin && !cgo)
 
-	(linux AND 386) OR (darwin AND (NOT cgo))
-
-A file may have multiple build constraints. The overall constraint is the AND
-of the individual constraints. That is, the build constraints:
-
-	// +build linux darwin
-	// +build amd64
-
-corresponds to the boolean formula:
-
-	(linux OR darwin) AND amd64
+It is an error for a file to have more than one //go:build line.
 
 During a particular build, the following words are satisfied:
 
@@ -853,22 +843,26 @@ in addition to ios tags and files.
 
 To keep a file from being considered for the build:
 
-	// +build ignore
+	//go:build ignore
 
 (any other unsatisfied word will work as well, but "ignore" is conventional.)
 
 To build a file only when using cgo, and only on Linux and OS X:
 
-	// +build linux,cgo darwin,cgo
+	//go:build cgo && (linux || darwin)
 
 Such a file is usually paired with another file implementing the
 default functionality for other systems, which in this case would
 carry the constraint:
 
-	// +build !linux,!darwin !cgo
+	//go:build !(cgo && (linux || darwin))
 
 Naming a file dns_windows.go will cause it to be included only when
 building the package for Windows; similarly, math_386.s will be included
 only when building the package for 32-bit x86.
+
+Go versions 1.16 and earlier used a different syntax for build constraints,
+with a "// +build" prefix. The gofmt command will add an equivalent //go:build
+constraint when encountering the older syntax.
 `,
 }

src/cmd/go/internal/imports/read.go

@@ -8,6 +8,7 @@ package imports
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
 	"io"
 	"unicode/utf8"
@@ -22,6 +23,19 @@ type importReader struct {
 	nerr int
 }
 
+var bom = []byte{0xef, 0xbb, 0xbf}
+
+func newImportReader(b *bufio.Reader) *importReader {
+	// Remove leading UTF-8 BOM.
+	// Per https://golang.org/ref/spec#Source_code_representation:
+	// a compiler may ignore a UTF-8-encoded byte order mark (U+FEFF)
+	// if it is the first Unicode code point in the source text.
+	if leadingBytes, err := b.Peek(3); err == nil && bytes.Equal(leadingBytes, bom) {
+		b.Discard(3)
+	}
+	return &importReader{b: b}
+}
+
 func isIdent(c byte) bool {
 	return 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z' || '0' <= c && c <= '9' || c == '_' || c >= utf8.RuneSelf
 }
@@ -201,7 +215,7 @@ func (r *importReader) readImport(imports *[]string) {
 // ReadComments is like io.ReadAll, except that it only reads the leading
 // block of comments in the file.
 func ReadComments(f io.Reader) ([]byte, error) {
-	r := &importReader{b: bufio.NewReader(f)}
+	r := newImportReader(bufio.NewReader(f))
 	r.peekByte(true)
 	if r.err == nil && !r.eof {
 		// Didn't reach EOF, so must have found a non-space byte. Remove it.
@@ -213,7 +227,7 @@ func ReadComments(f io.Reader) ([]byte, error) {
 // ReadImports is like io.ReadAll, except that it expects a Go file as input
 // and stops reading the input once the imports have completed.
 func ReadImports(f io.Reader, reportSyntaxError bool, imports *[]string) ([]byte, error) {
-	r := &importReader{b: bufio.NewReader(f)}
+	r := newImportReader(bufio.NewReader(f))
 
 	r.readKeyword("package")
 	r.readIdent()

src/cmd/go/internal/imports/read_test.go

@@ -66,6 +66,10 @@ var readImportsTests = []readTest{
 		`,
 		"",
 	},
+	{
+		"\ufeff𝔻" + `package p; import "x";ℙvar x = 1`,
+		"",
+	},
 }
 
 var readCommentsTests = []readTest{
@@ -81,6 +85,10 @@ var readCommentsTests = []readTest{
 		`ℙpackage p; import . "x"`,
 		"",
 	},
+	{
+		"\ufeff𝔻" + `ℙpackage p; import . "x"`,
+		"",
+	},
 	{
 		`// foo
 
@@ -90,6 +98,19 @@ var readCommentsTests = []readTest{
 		
 		/*/ zot */
 
+		// asdf
+		ℙHello, world`,
+		"",
+	},
+	{
+		"\ufeff𝔻" + `// foo
+
+		/* bar */
+
+		/* quux */ // baz
+
+		/*/ zot */
+
 		// asdf
 		ℙHello, world`,
 		"",
@@ -107,6 +128,11 @@ func testRead(t *testing.T, tests []readTest, read func(io.Reader) ([]byte, erro
 			in = tt.in[:j] + tt.in[j+len("ℙ"):]
 			testOut = tt.in[:j]
 		}
+		d := strings.Index(tt.in, "𝔻")
+		if d >= 0 {
+			in = in[:d] + in[d+len("𝔻"):]
+			testOut = testOut[d+len("𝔻"):]
+		}
 		r := strings.NewReader(in)
 		buf, err := read(r)
 		if err != nil {

src/cmd/go/testdata/script/build_ignore_leading_bom.txt

@@ -0,0 +1,27 @@
+# Per https://golang.org/ref/spec#Source_code_representation:
+# a compiler may ignore a UTF-8-encoded byte order mark (U+FEFF)
+# if it is the first Unicode code point in the source text.
+
+go list -f 'Imports: {{.Imports}} EmbedFiles: {{.EmbedFiles}}' .
+stdout '^Imports: \[embed m/hello\] EmbedFiles: \[.*file\]$'
+
+-- go.mod --
+module m
+
+go 1.16
+-- m.go --
+package main
+
+import (
+	_ "embed"
+
+	"m/hello"
+)
+
+//go:embed file
+var s string
+
+-- hello/hello.go --
+package hello
+
+-- file --

src/cmd/internal/sys/supported.go

@@ -74,7 +74,7 @@ func BuildModeSupported(compiler, buildmode, goos, goarch string) bool {
 			"android/amd64", "android/arm", "android/arm64", "android/386",
 			"freebsd/amd64",
 			"darwin/amd64", "darwin/arm64",
-			"windows/amd64", "windows/386":
+			"windows/amd64", "windows/386", "windows/arm64":
 			return true
 		}
 		return false

src/cmd/link/internal/ld/elf.go

@@ -950,6 +950,11 @@ func elfdynhash(ctxt *Link) {
 	}
 
 	s = ldr.CreateSymForUpdate(".dynamic", 0)
+	if ctxt.BuildMode == BuildModePIE {
+		// https://github.com/bminor/glibc/blob/895ef79e04a953cac1493863bcae29ad85657ee1/elf/elf.h#L986
+		const DTFLAGS_1_PIE = 0x08000000
+		Elfwritedynent(ctxt.Arch, s, elf.DT_FLAGS_1, uint64(DTFLAGS_1_PIE))
+	}
 	elfverneed = nfile
 	if elfverneed != 0 {
 		elfWriteDynEntSym(ctxt, s, elf.DT_VERNEED, gnuVersionR.Sym())

src/debug/elf/file.go

@@ -1164,6 +1164,13 @@ func (f *File) DWARF() (*dwarf.Data, error) {
 			b = dbuf
 		}
 
+		if f.Type == ET_EXEC {
+			// Do not apply relocations to DWARF sections for ET_EXEC binaries.
+			// Relocations should already be applied, and .rela sections may
+			// contain incorrect data.
+			return b, nil
+		}
+
 		for _, r := range f.Sections {
 			if r.Type != SHT_RELA && r.Type != SHT_REL {
 				continue

src/go/build/doc.go

@@ -59,7 +59,7 @@
 //
 // A build constraint, also known as a build tag, is a line comment that begins
 //
-// 	// +build
+// 	//go:build
 //
 // that lists the conditions under which a file should be included in the
 // package. Build constraints may also be part of a file's name

src/go/build/read.go

@@ -6,6 +6,7 @@ package build
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
 	"fmt"
 	"go/ast"
@@ -28,9 +29,19 @@ type importReader struct {
 	pos  token.Position
 }
 
+var bom = []byte{0xef, 0xbb, 0xbf}
+
 func newImportReader(name string, r io.Reader) *importReader {
+	b := bufio.NewReader(r)
+	// Remove leading UTF-8 BOM.
+	// Per https://golang.org/ref/spec#Source_code_representation:
+	// a compiler may ignore a UTF-8-encoded byte order mark (U+FEFF)
+	// if it is the first Unicode code point in the source text.
+	if leadingBytes, err := b.Peek(3); err == nil && bytes.Equal(leadingBytes, bom) {
+		b.Discard(3)
+	}
 	return &importReader{
-		b: bufio.NewReader(r),
+		b: b,
 		pos: token.Position{
 			Filename: name,
 			Line:     1,

src/go/build/read_test.go

@@ -66,6 +66,10 @@ var readGoInfoTests = []readTest{
 		`,
 		"",
 	},
+	{
+		"\ufeff𝔻" + `package p; import "x";ℙvar x = 1`,
+		"",
+	},
 }
 
 var readCommentsTests = []readTest{
@@ -81,6 +85,10 @@ var readCommentsTests = []readTest{
 		`ℙpackage p; import . "x"`,
 		"",
 	},
+	{
+		"\ufeff𝔻" + `ℙpackage p; import . "x"`,
+		"",
+	},
 	{
 		`// foo
 
@@ -90,6 +98,19 @@ var readCommentsTests = []readTest{
 
 		/*/ zot */
 
+		// asdf
+		ℙHello, world`,
+		"",
+	},
+	{
+		"\ufeff𝔻" + `// foo
+
+		/* bar */
+
+		/* quux */ // baz
+
+		/*/ zot */
+
 		// asdf
 		ℙHello, world`,
 		"",
@@ -107,6 +128,11 @@ func testRead(t *testing.T, tests []readTest, read func(io.Reader) ([]byte, erro
 			in = tt.in[:j] + tt.in[j+len("ℙ"):]
 			testOut = tt.in[:j]
 		}
+		d := strings.Index(tt.in, "𝔻")
+		if d >= 0 {
+			in = in[:d] + in[d+len("𝔻"):]
+			testOut = testOut[d+len("𝔻"):]
+		}
 		r := strings.NewReader(in)
 		buf, err := read(r)
 		if err != nil {
@@ -264,6 +290,12 @@ var readEmbedTests = []struct {
 		 test:3:14:y
 		 test:3:16:z`,
 	},
+	{
+		"\ufeffpackage p\nimport \"embed\"\n//go:embed x y z\nvar files embed.FS",
+		`test:3:12:x
+		 test:3:14:y
+		 test:3:16:z`,
+	},
 	{
 		"package p\nimport \"embed\"\nvar s = \"/*\"\n//go:embed x\nvar files embed.FS",
 		`test:4:12:x`,
@@ -292,6 +324,10 @@ var readEmbedTests = []struct {
 		"package p\n//go:embed x y z\nvar files embed.FS", // no import, no scan
 		"",
 	},
+	{
+		"\ufeffpackage p\n//go:embed x y z\nvar files embed.FS", // no import, no scan
+		"",
+	},
 }
 
 func TestReadEmbed(t *testing.T) {

src/internal/bytealg/index_generic.go

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// go:build !amd64 && !arm64 && !s390x && !ppc64le && !ppc64
 //go:build !amd64 && !arm64 && !s390x && !ppc64le && !ppc64
 // +build !amd64,!arm64,!s390x,!ppc64le,!ppc64
 

src/internal/bytealg/index_native.go

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// go:build amd64 || arm64 || s390x || ppc64le || ppc64
 //go:build amd64 || arm64 || s390x || ppc64le || ppc64
 // +build amd64 arm64 s390x ppc64le ppc64
 

src/net/http/server.go

@@ -333,7 +333,7 @@ func (c *conn) hijackLocked() (rwc net.Conn, buf *bufio.ReadWriter, err error) {
 const bufferBeforeChunkingSize = 2048
 
 // chunkWriter writes to a response's conn buffer, and is the writer
-// wrapped by the response.bufw buffered writer.
+// wrapped by the response.w buffered writer.
 //
 // chunkWriter also is responsible for finalizing the Header, including
 // conditionally setting the Content-Type and setting a Content-Length
@@ -1529,12 +1529,12 @@ func (w *response) bodyAllowed() bool {
 // The Writers are wired together like:
 //
 // 1. *response (the ResponseWriter) ->
-// 2. (*response).w, a *bufio.Writer of bufferBeforeChunkingSize bytes
+// 2. (*response).w, a *bufio.Writer of bufferBeforeChunkingSize bytes ->
 // 3. chunkWriter.Writer (whose writeHeader finalizes Content-Length/Type)
-//    and which writes the chunk headers, if needed.
-// 4. conn.buf, a bufio.Writer of default (4kB) bytes, writing to ->
+//    and which writes the chunk headers, if needed ->
+// 4. conn.bufw, a *bufio.Writer of default (4kB) bytes, writing to ->
 // 5. checkConnErrorWriter{c}, which notes any non-nil error on Write
-//    and populates c.werr with it if so. but otherwise writes to:
+//    and populates c.werr with it if so, but otherwise writes to ->
 // 6. the rwc, the net.Conn.
 //
 // TODO(bradfitz): short-circuit some of the buffering when the

src/reflect/all_test.go

@@ -4371,7 +4371,7 @@ func TestConvertPanic(t *testing.T) {
 	if !v.Type().ConvertibleTo(pt) {
 		t.Errorf("[]byte should be convertible to *[8]byte")
 	}
-	shouldPanic("reflect: cannot convert slice with length 4 to array pointer with length 8", func() {
+	shouldPanic("reflect: cannot convert slice with length 4 to pointer to array with length 8", func() {
 		_ = v.Convert(pt)
 	})
 }

src/reflect/type.go

@@ -107,10 +107,14 @@ type Type interface {
 
 	// ConvertibleTo reports whether a value of the type is convertible to type u.
 	// Even if ConvertibleTo returns true, the conversion may still panic.
+	// For example, a slice of type []T is convertible to *[N]T,
+	// but the conversion will panic if its length is less than N.
 	ConvertibleTo(u Type) bool
 
 	// Comparable reports whether values of this type are comparable.
 	// Even if Comparable returns true, the comparison may still panic.
+	// For example, values of interface type are comparable,
+	// but the comparison will panic if their dynamic type is not comparable.
 	Comparable() bool
 
 	// Methods applicable only to some types, depending on Kind.

src/reflect/value.go

@@ -3067,7 +3067,7 @@ func cvtSliceArrayPtr(v Value, t Type) Value {
 	n := t.Elem().Len()
 	h := (*unsafeheader.Slice)(v.ptr)
 	if n > h.Len {
-		panic("reflect: cannot convert slice with length " + itoa.Itoa(h.Len) + " to array pointer with length " + itoa.Itoa(n))
+		panic("reflect: cannot convert slice with length " + itoa.Itoa(h.Len) + " to pointer to array with length " + itoa.Itoa(n))
 	}
 	return Value{t.common(), h.Data, v.flag&^(flagIndir|flagAddr|flagKindMask) | flag(Ptr)}
 }

src/runtime/proc.go

@@ -516,8 +516,8 @@ var (
 	allglock mutex
 	allgs    []*g
 
-	// allglen and allgptr are atomic variables that contain len(allg) and
-	// &allg[0] respectively. Proper ordering depends on totally-ordered
+	// allglen and allgptr are atomic variables that contain len(allgs) and
+	// &allgs[0] respectively. Proper ordering depends on totally-ordered
 	// loads and stores. Writes are protected by allglock.
 	//
 	// allgptr is updated before allglen. Readers should read allglen

src/syscall/exec_linux_test.go

@@ -318,6 +318,7 @@ func TestGroupCleanupUserNamespace(t *testing.T) {
 		"uid=0(root) gid=0(root) groups=0(root),65534",
 		"uid=0(root) gid=0(root) groups=0(root),65534(nobody),65534(nobody),65534(nobody),65534(nobody),65534(nobody),65534(nobody),65534(nobody),65534(nobody),65534(nobody),65534(nobody)", // Alpine; see https://golang.org/issue/19938
 		"uid=0(root) gid=0(root) groups=0(root) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023",                                                                               // CentOS with SELinux context, see https://golang.org/issue/34547
+		"uid=0(root) gid=0(root) groups=0(root),65534(nobody) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023",                                                                 // Fedora with SElinux context, see https://golang.org/issue/46752
 	}
 	for _, e := range expected {
 		if strOut == e {

src/syscall/syscall_windows_test.go

@@ -10,7 +10,6 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"runtime"
 	"strings"
 	"syscall"
 	"testing"
@@ -79,10 +78,8 @@ func TestTOKEN_ALL_ACCESS(t *testing.T) {
 
 func TestStdioAreInheritable(t *testing.T) {
 	testenv.MustHaveGoBuild(t)
+	testenv.MustHaveCGO(t)
 	testenv.MustHaveExecPath(t, "gcc")
-	if runtime.GOARCH == "arm64" || runtime.GOARCH == "arm" {
-		t.Skip("Powershell is not native on ARM; see golang.org/issues/46701")
-	}
 
 	tmpdir := t.TempDir()
 
@@ -114,18 +111,28 @@ func main() {}
 		t.Fatalf("failed to build go library: %s\n%s", err, out)
 	}
 
-	// run powershell script
-	psscript := fmt.Sprintf(`
-hostname;
-$signature = " [DllImport("%q")] public static extern void HelloWorld(); ";
-Add-Type -MemberDefinition $signature -Name World -Namespace Hello;
-[Hello.World]::HelloWorld();
-hostname;
-`, dll)
-	psscript = strings.ReplaceAll(psscript, "\n", "")
-	out, err = exec.Command("powershell", "-Command", psscript).CombinedOutput()
+	// build c exe
+	const exetext = `
+#include <stdlib.h>
+#include <windows.h>
+int main(int argc, char *argv[])
+{
+	system("hostname");
+	((void(*)(void))GetProcAddress(LoadLibraryA(%q), "HelloWorld"))();
+	system("hostname");
+	return 0;
+}
+`
+	exe := filepath.Join(tmpdir, "helloworld.exe")
+	cmd = exec.Command("gcc", "-o", exe, "-xc", "-")
+	cmd.Stdin = strings.NewReader(fmt.Sprintf(exetext, dll))
+	out, err = testenv.CleanCmdEnv(cmd).CombinedOutput()
 	if err != nil {
-		t.Fatalf("Powershell command failed: %v: %v", err, string(out))
+		t.Fatalf("failed to build c executable: %s\n%s", err, out)
+	}
+	out, err = exec.Command(exe).CombinedOutput()
+	if err != nil {
+		t.Fatalf("c program execution failed: %v: %v", err, string(out))
 	}
 
 	hostname, err := os.Hostname()
@@ -137,6 +144,6 @@ hostname;
 	have = strings.ReplaceAll(have, "\r", "")
 	want := fmt.Sprintf("%sHello World%s", hostname, hostname)
 	if have != want {
-		t.Fatalf("Powershell command output is wrong: got %q, want %q", have, want)
+		t.Fatalf("c program output is wrong: got %q, want %q", have, want)
 	}
 }

test/fixedbugs/issue46749.go

@@ -0,0 +1,37 @@
+// errorcheck
+
+// Copyright 2021 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.
+
+package p
+
+var s string
+var b bool
+var i int
+var iface interface{}
+
+var (
+	_ = "" + b   // ERROR "invalid operation.*mismatched types.*untyped string and bool"
+	_ = "" + i   // ERROR "invalid operation.*mismatched types.*untyped string and int"
+	_ = "" + nil // ERROR "invalid operation.*mismatched types.*untyped string and nil"
+)
+
+var (
+	_ = s + false // ERROR "invalid operation.*mismatched types.*string and untyped bool"
+	_ = s + 1     // ERROR "invalid operation.*mismatched types.*string and untyped int"
+	_ = s + nil   // ERROR "invalid operation.*mismatched types.*string and nil"
+)
+
+var (
+	_ = "" + false // ERROR "invalid operation.*mismatched types.*untyped string and untyped bool"
+	_ = "" + 1     // ERROR "invalid operation.*mismatched types.*untyped string and untyped int"
+)
+
+var (
+	_ = b + 1         // ERROR "invalid operation.*mismatched types.*bool and untyped int"
+	_ = i + false     // ERROR "invalid operation.*mismatched types.*int and untyped bool"
+	_ = iface + 1     // ERROR "invalid operation.*mismatched types.*interface {} and int"
+	_ = iface + 1.0   // ERROR "invalid operation.*mismatched types.*interface {} and float64"
+	_ = iface + false // ERROR "invalid operation.*mismatched types.*interface {} and bool"
+)

test/run.go

@@ -2089,6 +2089,7 @@ var excludedFiles = map[string]bool{
 	"fixedbugs/issue7525d.go":  true, // types2 reports init cycle error on different line - ok otherwise
 	"fixedbugs/issue7525e.go":  true, // types2 reports init cycle error on different line - ok otherwise
 	"fixedbugs/issue7525.go":   true, // types2 reports init cycle error on different line - ok otherwise
+	"fixedbugs/issue46749.go":  true, // types2 reports can not convert error instead of type mismatched
 	"fixedbugs/issue9691.go":   true, // "cannot assign to int(.autotmp_4)" (probably irgen's fault)
 
 	// tests that rely on -m diagnostics, which currently differ with -G=3