1 files changed, 260 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/base/print.go b/src/cmd/compile/internal/base/print.go
new file mode 100644
index 0000000000..6831b3ada3
--- /dev/null
+++ b/src/cmd/compile/internal/base/print.go
@@ -0,0 +1,260 @@
+// Copyright 2020 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 base
+
+import (
+	"fmt"
+	"os"
+	"runtime/debug"
+	"sort"
+	"strings"
+
+	"cmd/internal/objabi"
+	"cmd/internal/src"
+)
+
+// An errorMsg is a queued error message, waiting to be printed.
+type errorMsg struct {
+	pos src.XPos
+	msg string
+}
+
+// Pos is the current source position being processed,
+// printed by Errorf, ErrorfLang, Fatalf, and Warnf.
+var Pos src.XPos
+
+var (
+	errorMsgs       []errorMsg
+	numErrors       int // number of entries in errorMsgs that are errors (as opposed to warnings)
+	numSyntaxErrors int
+)
+
+// Errors returns the number of errors reported.
+func Errors() int {
+	return numErrors
+}
+
+// SyntaxErrors returns the number of syntax errors reported
+func SyntaxErrors() int {
+	return numSyntaxErrors
+}
+
+// addErrorMsg adds a new errorMsg (which may be a warning) to errorMsgs.
+func addErrorMsg(pos src.XPos, format string, args ...interface{}) {
+	msg := fmt.Sprintf(format, args...)
+	// Only add the position if know the position.
+	// See issue golang.org/issue/11361.
+	if pos.IsKnown() {
+		msg = fmt.Sprintf("%v: %s", FmtPos(pos), msg)
+	}
+	errorMsgs = append(errorMsgs, errorMsg{
+		pos: pos,
+		msg: msg + "\n",
+	})
+}
+
+// FmtPos formats pos as a file:line string.
+func FmtPos(pos src.XPos) string {
+	if Ctxt == nil {
+		return "???"
+	}
+	return Ctxt.OutermostPos(pos).Format(Flag.C == 0, Flag.L == 1)
+}
+
+// byPos sorts errors by source position.
+type byPos []errorMsg
+
+func (x byPos) Len() int           { return len(x) }
+func (x byPos) Less(i, j int) bool { return x[i].pos.Before(x[j].pos) }
+func (x byPos) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
+
+// FlushErrors sorts errors seen so far by line number, prints them to stdout,
+// and empties the errors array.
+func FlushErrors() {
+	Ctxt.Bso.Flush()
+	if len(errorMsgs) == 0 {
+		return
+	}
+	sort.Stable(byPos(errorMsgs))
+	for i, err := range errorMsgs {
+		if i == 0 || err.msg != errorMsgs[i-1].msg {
+			fmt.Printf("%s", err.msg)
+		}
+	}
+	errorMsgs = errorMsgs[:0]
+}
+
+// lasterror keeps track of the most recently issued error,
+// to avoid printing multiple error messages on the same line.
+var lasterror struct {
+	syntax src.XPos // source position of last syntax error
+	other  src.XPos // source position of last non-syntax error
+	msg    string   // error message of last non-syntax error
+}
+
+// sameline reports whether two positions a, b are on the same line.
+func sameline(a, b src.XPos) bool {
+	p := Ctxt.PosTable.Pos(a)
+	q := Ctxt.PosTable.Pos(b)
+	return p.Base() == q.Base() && p.Line() == q.Line()
+}
+
+// Errorf reports a formatted error at the current line.
+func Errorf(format string, args ...interface{}) {
+	ErrorfAt(Pos, format, args...)
+}
+
+// ErrorfAt reports a formatted error message at pos.
+func ErrorfAt(pos src.XPos, format string, args ...interface{}) {
+	msg := fmt.Sprintf(format, args...)
+
+	if strings.HasPrefix(msg, "syntax error") {
+		numSyntaxErrors++
+		// only one syntax error per line, no matter what error
+		if sameline(lasterror.syntax, pos) {
+			return
+		}
+		lasterror.syntax = pos
+	} else {
+		// only one of multiple equal non-syntax errors per line
+		// (flusherrors shows only one of them, so we filter them
+		// here as best as we can (they may not appear in order)
+		// so that we don't count them here and exit early, and
+		// then have nothing to show for.)
+		if sameline(lasterror.other, pos) && lasterror.msg == msg {
+			return
+		}
+		lasterror.other = pos
+		lasterror.msg = msg
+	}
+
+	addErrorMsg(pos, "%s", msg)
+	numErrors++
+
+	hcrash()
+	if numErrors >= 10 && Flag.LowerE == 0 {
+		FlushErrors()
+		fmt.Printf("%v: too many errors\n", FmtPos(pos))
+		ErrorExit()
+	}
+}
+
+// ErrorfVers reports that a language feature (format, args) requires a later version of Go.
+func ErrorfVers(lang string, format string, args ...interface{}) {
+	Errorf("%s requires %s or later (-lang was set to %s; check go.mod)", fmt.Sprintf(format, args...), lang, Flag.Lang)
+}
+
+// UpdateErrorDot is a clumsy hack that rewrites the last error,
+// if it was "LINE: undefined: NAME", to be "LINE: undefined: NAME in EXPR".
+// It is used to give better error messages for dot (selector) expressions.
+func UpdateErrorDot(line string, name, expr string) {
+	if len(errorMsgs) == 0 {
+		return
+	}
+	e := &errorMsgs[len(errorMsgs)-1]
+	if strings.HasPrefix(e.msg, line) && e.msg == fmt.Sprintf("%v: undefined: %v\n", line, name) {
+		e.msg = fmt.Sprintf("%v: undefined: %v in %v\n", line, name, expr)
+	}
+}
+
+// Warnf reports a formatted warning at the current line.
+// In general the Go compiler does NOT generate warnings,
+// so this should be used only when the user has opted in
+// to additional output by setting a particular flag.
+func Warn(format string, args ...interface{}) {
+	WarnfAt(Pos, format, args...)
+}
+
+// WarnfAt reports a formatted warning at pos.
+// In general the Go compiler does NOT generate warnings,
+// so this should be used only when the user has opted in
+// to additional output by setting a particular flag.
+func WarnfAt(pos src.XPos, format string, args ...interface{}) {
+	addErrorMsg(pos, format, args...)
+	if Flag.LowerM != 0 {
+		FlushErrors()
+	}
+}
+
+// Fatalf reports a fatal error - an internal problem - at the current line and exits.
+// If other errors have already been printed, then Fatalf just quietly exits.
+// (The internal problem may have been caused by incomplete information
+// after the already-reported errors, so best to let users fix those and
+// try again without being bothered about a spurious internal error.)
+//
+// But if no errors have been printed, or if -d panic has been specified,
+// Fatalf prints the error as an "internal compiler error". In a released build,
+// it prints an error asking to file a bug report. In development builds, it
+// prints a stack trace.
+//
+// If -h has been specified, Fatalf panics to force the usual runtime info dump.
+func Fatalf(format string, args ...interface{}) {
+	FatalfAt(Pos, format, args...)
+}
+
+// FatalfAt reports a fatal error - an internal problem - at pos and exits.
+// If other errors have already been printed, then FatalfAt just quietly exits.
+// (The internal problem may have been caused by incomplete information
+// after the already-reported errors, so best to let users fix those and
+// try again without being bothered about a spurious internal error.)
+//
+// But if no errors have been printed, or if -d panic has been specified,
+// FatalfAt prints the error as an "internal compiler error". In a released build,
+// it prints an error asking to file a bug report. In development builds, it
+// prints a stack trace.
+//
+// If -h has been specified, FatalfAt panics to force the usual runtime info dump.
+func FatalfAt(pos src.XPos, format string, args ...interface{}) {
+	FlushErrors()
+
+	if Debug.Panic != 0 || numErrors == 0 {
+		fmt.Printf("%v: internal compiler error: ", FmtPos(pos))
+		fmt.Printf(format, args...)
+		fmt.Printf("\n")
+
+		// If this is a released compiler version, ask for a bug report.
+		if strings.HasPrefix(objabi.Version, "go") {
+			fmt.Printf("\n")
+			fmt.Printf("Please file a bug report including a short program that triggers the error.\n")
+			fmt.Printf("https://golang.org/issue/new\n")
+		} else {
+			// Not a release; dump a stack trace, too.
+			fmt.Println()
+			os.Stdout.Write(debug.Stack())
+			fmt.Println()
+		}
+	}
+
+	hcrash()
+	ErrorExit()
+}
+
+// hcrash crashes the compiler when -h is set, to find out where a message is generated.
+func hcrash() {
+	if Flag.LowerH != 0 {
+		FlushErrors()
+		if Flag.LowerO != "" {
+			os.Remove(Flag.LowerO)
+		}
+		panic("-h")
+	}
+}
+
+// ErrorExit handles an error-status exit.
+// It flushes any pending errors, removes the output file, and exits.
+func ErrorExit() {
+	FlushErrors()
+	if Flag.LowerO != "" {
+		os.Remove(Flag.LowerO)
+	}
+	os.Exit(2)
+}
+
+// ExitIfErrors calls ErrorExit if any errors have been reported.
+func ExitIfErrors() {
+	if Errors() > 0 {
+		ErrorExit()
+	}
+}