cmd/compile: disallow "init" as alias

Fixes #17637.

Change-Id: I5af63b8277c0a0f9fef4880992bcb925ca088687
Reviewed-on: https://go-review.googlesource.com/32106Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/noder.go

@@ -214,8 +214,12 @@ func (p *noder) aliasDecl(decl *syntax.AliasDecl) {
 		return
 	}
 
-	// don't declare blank aliases
-	if decl.Name.Value == "_" {
+	// handle special cases
+	switch decl.Name.Value {
+	case "_":
+		return // don't declare blank aliases
+	case "init":
+		yyerror("cannot declare init - must be non-alias function declaration")
 		return
 	}
 

test/alias2.go

@@ -9,6 +9,7 @@
 package p
 
 import (
+	"flag"
 	"fmt" // use at most once (to test "imported but not used" error)
 	"go/build"
 	. "go/build"
@@ -74,13 +75,19 @@ func _ => math.Sin
 func sin => math.Sin
 func sin1 => math.Pi // ERROR "math.Pi is not a function"
 
+// aliases may not be called init
+func init => flag.Parse // ERROR "cannot declare init"
+
 // alias reference to a package marks package as used
 func _ => fmt.Println
 
 // re-exported aliases
 const Pi => math.Pi
+
 type Writer => io.Writer
+
 var Def => build.Default
+
 func Sin => math.Sin
 
 // type aliases denote identical types