gofmt: stability improvement

There are a variety of token pairs that if printed
without separating blank may combine into a different
token sequence. Most of these (except for INT + .)
don't happen at the moment due to the spacing
introduced between expression operands. However, this
will prevent errors should the expression spacing
change.

R=rsc
CC=golang-dev
https://golang.org/cl/2207044

diff --git a/src/pkg/go/printer/nodes.go b/src/pkg/go/printer/nodes.go
index 2451116fdb64f39e77d2d195c03f6051d88e47d2..3e8f12100b1393bf9bd1380126074bc19f8953dc 100644 (file)
--- a/src/pkg/go/printer/nodes.go
+++ b/src/pkg/go/printer/nodes.go
@@ -543,7 +543,7 @@ func walkBinary(e *ast.BinaryExpr) (has5, has6 bool, maxProblem int) {
 
        case *ast.UnaryExpr:
                switch e.Op.String() + r.Op.String() {
-               case "/*":
+               case "/*", "&&", "&^":
                        maxProblem = 6
                case "++", "--":
                        if maxProblem < 5 {
@@ -612,11 +612,14 @@ func reduceDepth(depth int) int {
 //     1) If there is a binary operator with a right side unary operand
 //        that would clash without a space, the cutoff must be (in order):
 //
-//             &^      7
 //             /*      7
+//             &&      7
+//             &^      7
 //             ++      6
 //             --      6
 //
+//         (Comparison operators always have spaces around them.)
+//
 //     2) If there is a mix of level 6 and level 5 operators, then the cutoff
 //        is 6 (use spaces to distinguish precedence) in Normal mode
 //        and 5 (never use spaces) in Compact mode.

diff --git a/src/pkg/go/printer/printer.go b/src/pkg/go/printer/printer.go
index b985f6ed3e21e9fcce4320b0fa3bcc5bcfead905..cdc8cf518d252afd390fe5b1dea309b91bfbde81 100644 (file)
--- a/src/pkg/go/printer/printer.go
+++ b/src/pkg/go/printer/printer.go
@@ -746,6 +746,26 @@ func (p *printer) writeWhitespace(n int) {
 // ----------------------------------------------------------------------------
 // Printing interface
 
+
+func mayCombine(prev token.Token, next byte) (b bool) {
+       switch prev {
+       case token.INT:
+               b = next == '.' // 1.
+       case token.ADD:
+               b = next == '+' // ++
+       case token.SUB:
+               b = next == '-' // --
+       case token.QUO:
+               b = next == '*' // /*
+       case token.LSS:
+               b = next == '-' || next == '<' // <- or <<
+       case token.AND:
+               b = next == '&' || next == '^' // && or &^
+       }
+       return
+}
+
+
 // print prints a list of "items" (roughly corresponding to syntactic
 // tokens, but also including whitespace and formatting information).
 // It is the only print function that should be called directly from
@@ -803,8 +823,13 @@ func (p *printer) print(args ...interface{}) {
                        tok = x.Kind
                case token.Token:
                        s := x.String()
-                       if p.lastTok == token.INT && s[0] == '.' {
-                               // separate int with blank from '.' so it doesn't become a float
+                       if mayCombine(p.lastTok, s[0]) {
+                               // the previous and the current token must be
+                               // separated by a blank otherwise they combine
+                               // into a different incorrect token sequence
+                               // (except for token.INT followed by a '.' this
+                               // should never happen because it is taken care
+                               // of via binary expression formatting)
                                if len(p.buffer) != 0 {
                                        p.internalError("whitespace buffer not empty")
                                }

diff --git a/src/pkg/go/printer/testdata/expressions.golden b/src/pkg/go/printer/testdata/expressions.golden
index 02bae49b48d5788944ca746fe07ea29edada3dc8..b5dac45a7bb731919f764f5f92a59b509be28d63 100644 (file)
--- a/src/pkg/go/printer/testdata/expressions.golden
+++ b/src/pkg/go/printer/testdata/expressions.golden
@@ -194,6 +194,17 @@ func f(x int, args ...int) {
        _ = .42.x
        _ = 42e0.x
        _ = 42e0.x
+
+       // a blank must remain between the binary operator and the 2nd operand
+       _ = x / *y
+       _ = x < -1
+       _ = x < <-1
+       _ = x + +1
+       _ = x - -1
+       _ = x & &x
+       _ = x & ^x
+
+       _ = f(x / *y, x < -1, x < <-1, x + +1, x - -1, x & &x, x & ^x)
 }
 
 

diff --git a/src/pkg/go/printer/testdata/expressions.input b/src/pkg/go/printer/testdata/expressions.input
index 7d5889b064bc6200bc1fb9e66bc39e5857dae925..3eb1629317a9aa77cdf6f2714fd12271e3aadd7c 100644 (file)
--- a/src/pkg/go/printer/testdata/expressions.input
+++ b/src/pkg/go/printer/testdata/expressions.input
@@ -194,6 +194,17 @@ func f(x int, args ...int) {
        _ = .42.x
        _ = 42e0 .x
        _ = 42e0.x
+
+       // a blank must remain between the binary operator and the 2nd operand
+       _ = x/ *y
+       _ = x< -1
+       _ = x< <-1
+       _ = x+ +1
+       _ = x- -1
+       _ = x& &x
+       _ = x& ^x
+
+       _ = f(x/ *y, x< -1, x< <-1, x+ +1, x- -1, x& &x, x& ^x)
 }
 
 

diff --git a/src/pkg/go/printer/testdata/expressions.raw b/src/pkg/go/printer/testdata/expressions.raw
index 9e83892e87b6da09bc6f6373d0ba083ff893b5af..e571d08284cbaf976d4befdec296d20f820702be 100644 (file)
--- a/src/pkg/go/printer/testdata/expressions.raw
+++ b/src/pkg/go/printer/testdata/expressions.raw
@@ -194,6 +194,17 @@ func f(x int, args ...int) {
        _ = .42.x
        _ = 42e0.x
        _ = 42e0.x
+
+       // a blank must remain between the binary operator and the 2nd operand
+       _ = x / *y
+       _ = x < -1
+       _ = x < <-1
+       _ = x + +1
+       _ = x - -1
+       _ = x & &x
+       _ = x & ^x
+
+       _ = f(x / *y, x < -1, x < <-1, x + +1, x - -1, x & &x, x & ^x)
 }