cmd/compile/internal/gc: cleaning lex.go

Cleaning along the way:
-convert variable types from int to bool
-remove unnecessary functions
-remove unnecessary type conversion
-remove unnecessary variable declarations
-transform struct{string,string} with lookup to map[string]string

This change passes go build -toolexec 'toolstash -cmp' -a std.

Change-Id: I259728fe4afd7f23b67f08fab856ce0abee57b21
Reviewed-on: https://go-review.googlesource.com/14435Reviewed-by: Ian Lance Taylor <iant@golang.org>

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

@@ -382,12 +382,12 @@ type Sig struct {
 type Io struct {
 	infile     string
 	bin        *obj.Biobuf
-	nlsemi     int
-	eofnl      int
+	cp         string // used for content when bin==nil
 	last       int
 	peekc      int
-	peekc1     int    // second peekc for ...
-	cp         string // used for content when bin==nil
+	peekc1     int // second peekc for ...
+	nlsemi     bool
+	eofnl      bool
 	importsafe bool
 }
 
@@ -598,7 +598,7 @@ var incannedimport int
 
 var statuniqgen int // name generator for static temps
 
-var loophack int
+var loophack bool
 
 var iota_ int32
 

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

@@ -2311,6 +2311,6 @@ func fixlbrace(lbr int) {
 	// set up for another one now that we're done.
 	// See comment in lex.C about loophack.
 	if lbr == LBODY {
-		loophack = 1
+		loophack = true
 	}
 }

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

@@ -122,7 +122,7 @@ func Yyerror(format string, args ...interface{}) {
 
 		// An unexpected EOF caused a syntax error. Use the previous
 		// line number since getc generated a fake newline character.
-		if curio.eofnl != 0 {
+		if curio.eofnl {
 			lexlineno = prevlineno
 		}
 

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

@@ -18,15 +18,19 @@ func atoi(s string) int {
 	return int(n)
 }
 
-func isalnum(c int) bool {
-	return isalpha(c) || isdigit(c)
+func isSpace(c int) bool {
+	return c == ' ' || c == '\t' || c == '\n' || c == '\r'
 }
 
-func isalpha(c int) bool {
+func isAlnum(c int) bool {
+	return isAlpha(c) || isDigit(c)
+}
+
+func isAlpha(c int) bool {
 	return 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z'
 }
 
-func isdigit(c int) bool {
+func isDigit(c int) bool {
 	return '0' <= c && c <= '9'
 }
 

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

@@ -160,7 +160,7 @@ func fixlbrace(lbr int) {
 	// set up for another one now that we're done.
 	// See comment in lex.C about loophack.
 	if lbr == LBODY {
-		loophack = 1
+		loophack = true
 	}
 }