cmd/compile: remove -importmap flag

Obsoleted by -importcfg, and no longer used by anything.

Updates #51225.

Change-Id: I49e646d2728347f862f90805051bb03dd4f4bed2
Reviewed-on: https://go-review.googlesource.com/c/go/+/415235
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/doc.go

@@ -68,9 +68,6 @@ Flags:
 	-importcfg file
 		Read import configuration from file.
 		In the file, set importmap, packagefile to specify import resolution.
-	-importmap old=new
-		Interpret import "old" as import "new" during compilation.
-		The option may be repeated to add multiple mappings.
 	-installsuffix suffix
 		Look for packages in $GOROOT/pkg/$GOOS_$GOARCH_suffix
 		instead of $GOROOT/pkg/$GOOS_$GOARCH.

src/cmd/compile/internal/base/flag.go

@@ -100,7 +100,6 @@ type CmdFlags struct {
 	GenDwarfInl        int          "help:\"generate DWARF inline info records\"" // 0=disabled, 1=funcs, 2=funcs+formals/locals
 	GoVersion          string       "help:\"required version of the runtime\""
 	ImportCfg          func(string) "help:\"read import configuration from `file`\""
-	ImportMap          func(string) "help:\"add `definition` of the form source=actual to import map\""
 	InstallSuffix      string       "help:\"set pkg directory `suffix`\""
 	JSON               string       "help:\"version,file for JSON compiler/optimizer detail output\""
 	Lang               string       "help:\"Go language version source code expects\""
@@ -130,7 +129,7 @@ type CmdFlags struct {
 			Files    map[string]string
 		}
 		ImportDirs   []string          // appended to by -I
-		ImportMap    map[string]string // set by -importmap OR -importcfg
+		ImportMap    map[string]string // set by -importcfg
 		PackageFile  map[string]string // set by -importcfg; nil means not in use
 		SpectreIndex bool              // set by -spectre=index or -spectre=all
 		// Whether we are adding any sort of code instrumentation, such as
@@ -156,7 +155,6 @@ func ParseFlags() {
 	Flag.EmbedCfg = readEmbedCfg
 	Flag.GenDwarfInl = 2
 	Flag.ImportCfg = readImportCfg
-	Flag.ImportMap = addImportMap
 	Flag.LinkShared = &Ctxt.Flag_linkshared
 	Flag.Shared = &Ctxt.Flag_shared
 	Flag.WB = true
@@ -388,21 +386,6 @@ func addImportDir(dir string) {
 	}
 }
 
-func addImportMap(s string) {
-	if Flag.Cfg.ImportMap == nil {
-		Flag.Cfg.ImportMap = make(map[string]string)
-	}
-	if strings.Count(s, "=") != 1 {
-		log.Fatal("-importmap argument must be of the form source=actual")
-	}
-	i := strings.Index(s, "=")
-	source, actual := s[:i], s[i+1:]
-	if source == "" || actual == "" {
-		log.Fatal("-importmap argument must be of the form source=actual; source and actual must be non-empty")
-	}
-	Flag.Cfg.ImportMap[source] = actual
-}
-
 func readImportCfg(file string) {
 	if Flag.Cfg.ImportMap == nil {
 		Flag.Cfg.ImportMap = make(map[string]string)