cmd/link: make dwarf name slice index self-describing

cmd/compile/internal/dwarfgen.createComplexVar does it this way, which
has the nice property of documenting the expected prefix.

This is primarily for newtype, since defgotype checks for the prefix
immediately prior, but I changed both for consistency.

Change-Id: I49fa7c6166bdcbd19aaf91fe3dc20537080afcfc
Reviewed-on: https://go-review.googlesource.com/c/go/+/635177
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Pratt <mpratt@google.com>

diff --git a/src/cmd/link/internal/ld/dwarf.go b/src/cmd/link/internal/ld/dwarf.go
index 14c0b687d853a32fea3b95a5c5db347aa9b02ea5..b653e09a3c1b9130e0a01702bacd0e58eb5e7d8a 100644 (file)
--- a/src/cmd/link/internal/ld/dwarf.go
+++ b/src/cmd/link/internal/ld/dwarf.go
@@ -520,7 +520,7 @@ func (d *dwctxt) defgotype(gotype loader.Sym) loader.Sym {
                d.linkctxt.Errorf(gotype, "dwarf: type name doesn't start with \"type:\"")
                return d.mustFind("<unspecified>")
        }
-       name := sn[5:] // could also decode from Type.string
+       name := sn[len("type:"):] // could also decode from Type.string
 
        sdie := d.find(name)
        if sdie != 0 {
@@ -534,7 +534,7 @@ func (d *dwctxt) defgotype(gotype loader.Sym) loader.Sym {
 
 func (d *dwctxt) newtype(gotype loader.Sym) *dwarf.DWDie {
        sn := d.ldr.SymName(gotype)
-       name := sn[5:] // could also decode from Type.string
+       name := sn[len("type:"):] // could also decode from Type.string
        tdata := d.ldr.Data(gotype)
        if len(tdata) == 0 {
                d.linkctxt.Errorf(gotype, "missing type")