all: simplify multiple for loops

If a for loop has a simple condition and begins with a simple
"if x { break; }"; we can simply add "!x" to the loop's condition.

While at it, simplify a few assignments to use the common pattern
"x := staticDefault; if cond { x = otherValue(); }".

Finally, simplify a couple of var declarations.

Change-Id: I413982c6abd32905adc85a9a666cb3819139c19f
Reviewed-on: https://go-review.googlesource.com/c/go/+/165342
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

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

@@ -553,11 +553,9 @@ func createDwarfVars(fnsym *obj.LSym, fn *Func, automDecls []*Node) ([]*Node, []
 		decls, vars, selected = createSimpleVars(automDecls)
 	}
 
-	var dcl []*Node
+	dcl := automDecls
 	if fnsym.WasInlined() {
 		dcl = preInliningDcls(fnsym)
-	} else {
-		dcl = automDecls
 	}
 
 	// If optimization is enabled, the list above will typically be

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

@@ -477,12 +477,10 @@ func dimportpath(p *types.Pkg) {
 		return
 	}
 
-	var str string
+	str := p.Path
 	if p == localpkg {
 		// Note: myimportpath != "", or else dgopkgpath won't call dimportpath.
 		str = myimportpath
-	} else {
-		str = p.Path
 	}
 
 	s := Ctxt.Lookup("type..importpath." + p.Prefix + ".")

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

@@ -3116,11 +3116,9 @@ func walkcompare(n *Node, init *Nodes) *Node {
 	if l != nil {
 		// Handle both == and !=.
 		eq := n.Op
-		var andor Op
+		andor := OOROR
 		if eq == OEQ {
 			andor = OANDAND
-		} else {
-			andor = OOROR
 		}
 		// Check for types equal.
 		// For empty interface, this is:

src/cmd/compile/internal/ssa/schedule.go

@@ -233,14 +233,10 @@ func schedule(f *Func) {
 		// Schedule highest priority value, update use counts, repeat.
 		order = order[:0]
 		tuples := make(map[ID][]*Value)
-		for {
+		for priq.Len() > 0 {
 			// Find highest priority schedulable value.
 			// Note that schedule is assembled backwards.
 
-			if priq.Len() == 0 {
-				break
-			}
-
 			v := heap.Pop(priq).(*Value)
 
 			// Add it to the schedule.

src/cmd/internal/obj/pass.go

@@ -141,10 +141,7 @@ func linkpatch(ctxt *Link, sym *LSym, newprog ProgAlloc) {
 			continue
 		}
 		q := sym.Func.Text
-		for q != nil {
-			if p.To.Offset == q.Pc {
-				break
-			}
+		for q != nil && p.To.Offset != q.Pc {
 			if q.Forwd != nil && p.To.Offset >= q.Forwd.Pc {
 				q = q.Forwd
 			} else {

src/cmd/link/internal/ld/elf.go

@@ -1290,11 +1290,9 @@ func elfshreloc(arch *sys.Arch, sect *sym.Section) *ElfShdr {
 		return nil
 	}
 
-	var typ int
+	typ := SHT_REL
 	if elfRelType == ".rela" {
 		typ = SHT_RELA
-	} else {
-		typ = SHT_REL
 	}
 
 	sh := elfshname(elfRelType + sect.Name)

src/encoding/json/encode.go

@@ -1069,8 +1069,7 @@ func typeFields(t reflect.Type) []field {
 	next := []field{{typ: t}}
 
 	// Count of queued names for current level and the next.
-	count := map[reflect.Type]int{}
-	nextCount := map[reflect.Type]int{}
+	var count, nextCount map[reflect.Type]int
 
 	// Types already visited at an earlier level.
 	visited := map[reflect.Type]bool{}

src/encoding/json/stream_test.go

@@ -296,7 +296,7 @@ type decodeThis struct {
 	v interface{}
 }
 
-var tokenStreamCases []tokenStreamCase = []tokenStreamCase{
+var tokenStreamCases = []tokenStreamCase{
 	// streaming token cases
 	{json: `10`, expTokens: []interface{}{float64(10)}},
 	{json: ` [10] `, expTokens: []interface{}{

src/internal/reflectlite/type.go

@@ -510,10 +510,7 @@ func (t *rtype) Name() string {
 	}
 	s := t.String()
 	i := len(s) - 1
-	for i >= 0 {
-		if s[i] == '.' {
-			break
-		}
+	for i >= 0 && s[i] != '.' {
 		i--
 	}
 	return s[i+1:]

src/reflect/type.go

@@ -875,10 +875,7 @@ func (t *rtype) Name() string {
 	}
 	s := t.String()
 	i := len(s) - 1
-	for i >= 0 {
-		if s[i] == '.' {
-			break
-		}
+	for i >= 0 && s[i] != '.' {
 		i--
 	}
 	return s[i+1:]

src/runtime/traceback.go

@@ -1289,10 +1289,7 @@ func printCgoTraceback(callers *cgoCallers) {
 func printOneCgoTraceback(pc uintptr, max int, arg *cgoSymbolizerArg) int {
 	c := 0
 	arg.pc = pc
-	for {
-		if c > max {
-			break
-		}
+	for c <= max {
 		callCgoSymbolizer(arg)
 		if arg.funcName != nil {
 			// Note that we don't print any argument

src/runtime/type.go

@@ -118,10 +118,7 @@ func (t *_type) name() string {
 	}
 	s := t.string()
 	i := len(s) - 1
-	for i >= 0 {
-		if s[i] == '.' {
-			break
-		}
+	for i >= 0 && s[i] != '.' {
 		i--
 	}
 	return s[i+1:]

src/text/template/funcs.go

@@ -263,11 +263,9 @@ func call(fn reflect.Value, args ...reflect.Value) (reflect.Value, error) {
 	for i, arg := range args {
 		value := indirectInterface(arg)
 		// Compute the expected type. Clumsy because of variadics.
-		var argType reflect.Type
+		argType := dddType
 		if !typ.IsVariadic() || i < numIn-1 {
 			argType = typ.In(i)
-		} else {
-			argType = dddType
 		}
 
 		var err error