cmd/compile: clean up methodsym

Convert yyerrors into Fatals.
Remove the goto.
Move variable declaration closer to use.
Unify printing strings a bit.
Convert an int param into a bool.

Passes toolstash-check. No compiler performance impact.

Change-Id: I9017681417b785cf8693d18b124ac4f1ff37f2b5
Reviewed-on: https://go-review.googlesource.com/39170
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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

@@ -956,56 +956,48 @@ func functypefield0(t *Type, this *Field, in, out []*Field) {
 
 var methodsym_toppkg *Pkg
 
-func methodsym(nsym *Sym, t0 *Type, iface int) *Sym {
-	var s *Sym
-	var p string
-	var suffix string
-	var spkg *Pkg
+func methodsym(nsym *Sym, t0 *Type, iface bool) *Sym {
+	if t0 == nil {
+		Fatalf("methodsym: nil receiver type")
+	}
 
 	t := t0
-	if t == nil {
-		goto bad
-	}
-	s = t.Sym
+	s := t.Sym
 	if s == nil && t.IsPtr() {
 		t = t.Elem()
 		if t == nil {
-			goto bad
+			Fatalf("methodsym: ptrto nil")
 		}
 		s = t.Sym
 	}
 
-	spkg = nil
-	if s != nil {
-		spkg = s.Pkg
-	}
-
 	// if t0 == *t and t0 has a sym,
 	// we want to see *t, not t0, in the method name.
 	if t != t0 && t0.Sym != nil {
 		t0 = typPtr(t)
 	}
 
-	suffix = ""
-	if iface != 0 {
+	suffix := ""
+	if iface {
 		dowidth(t0)
 		if t0.Width < int64(Widthptr) {
 			suffix = "·i"
 		}
 	}
 
+	var spkg *Pkg
+	if s != nil {
+		spkg = s.Pkg
+	}
+	pkgprefix := ""
 	if (spkg == nil || nsym.Pkg != spkg) && !exportname(nsym.Name) {
-		if t0.Sym == nil && t0.IsPtr() {
-			p = fmt.Sprintf("(%-S).%s.%s%s", t0, nsym.Pkg.Prefix, nsym.Name, suffix)
-		} else {
-			p = fmt.Sprintf("%-S.%s.%s%s", t0, nsym.Pkg.Prefix, nsym.Name, suffix)
-		}
+		pkgprefix = "." + nsym.Pkg.Prefix
+	}
+	var p string
+	if t0.Sym == nil && t0.IsPtr() {
+		p = fmt.Sprintf("(%-S)%s.%s%s", t0, pkgprefix, nsym.Name, suffix)
 	} else {
-		if t0.Sym == nil && t0.IsPtr() {
-			p = fmt.Sprintf("(%-S).%s%s", t0, nsym.Name, suffix)
-		} else {
-			p = fmt.Sprintf("%-S.%s%s", t0, nsym.Name, suffix)
-		}
+		p = fmt.Sprintf("%-S%s.%s%s", t0, pkgprefix, nsym.Name, suffix)
 	}
 
 	if spkg == nil {
@@ -1015,13 +1007,7 @@ func methodsym(nsym *Sym, t0 *Type, iface int) *Sym {
 		spkg = methodsym_toppkg
 	}
 
-	s = spkg.Lookup(p)
-
-	return s
-
-bad:
-	yyerror("illegal receiver type: %v", t0)
-	return nil
+	return spkg.Lookup(p)
 }
 
 // methodname is a misnomer because this now returns a Sym, rather

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

@@ -356,8 +356,8 @@ func methods(t *Type) []*Sig {
 			sig.pkg = method.Pkg
 		}
 
-		sig.isym = methodsym(method, it, 1)
-		sig.tsym = methodsym(method, t, 0)
+		sig.isym = methodsym(method, it, true)
+		sig.tsym = methodsym(method, t, false)
 		sig.type_ = methodfunc(f.Type, t)
 		sig.mtype = methodfunc(f.Type, nil)
 
@@ -423,7 +423,7 @@ func imethods(t *Type) []*Sig {
 		// IfaceType.Method is not in the reflect data.
 		// Generate the method body, so that compiled
 		// code can refer to it.
-		isym := methodsym(method, t, 0)
+		isym := methodsym(method, t, false)
 		if !isym.Siggen() {
 			isym.SetSiggen(true)
 			genwrapper(t, f, isym, 0)

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

@@ -1783,7 +1783,7 @@ func genwrapper(rcvr *Type, method *Field, newnam *Sym, iface int) {
 		as.Right.Type = rcvr
 		fn.Nbody.Append(as)
 		n := nod(ORETJMP, nil, nil)
-		n.Left = newname(methodsym(method.Sym, methodrcvr, 0))
+		n.Left = newname(methodsym(method.Sym, methodrcvr, false))
 		fn.Nbody.Append(n)
 		// When tail-calling, we can't use a frame pointer.
 		fn.Func.SetNoFramePointer(true)

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

@@ -2384,7 +2384,7 @@ func looktypedot(n *Node, t *Type, dostrcmp int) bool {
 			return false
 		}
 
-		n.Sym = methodsym(n.Sym, t, 0)
+		n.Sym = methodsym(n.Sym, t, false)
 		n.Xoffset = f1.Offset
 		n.Type = f1.Type
 		n.Op = ODOTINTER
@@ -2410,7 +2410,7 @@ func looktypedot(n *Node, t *Type, dostrcmp int) bool {
 		return false
 	}
 
-	n.Sym = methodsym(n.Sym, t, 0)
+	n.Sym = methodsym(n.Sym, t, false)
 	n.Xoffset = f2.Offset
 	n.Type = f2.Type
 	n.Op = ODOTMETH
@@ -2529,7 +2529,7 @@ func lookdot(n *Node, t *Type, dostrcmp int) *Field {
 			return nil
 		}
 
-		n.Sym = methodsym(n.Sym, n.Left.Type, 0)
+		n.Sym = methodsym(n.Sym, n.Left.Type, false)
 		n.Xoffset = f2.Offset
 		n.Type = f2.Type