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go/printer: do not remove parens around composite literals starting with a type name in control clauses

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(even when they are nested inside an expression).

Fixes #1243.

R=rsc
CC=golang-dev
https://golang.org/cl/2817041
This commit is contained in:
Robert Griesemer 2010-11-01 15:08:03 -07:00
parent 9384fdc96a
commit 7996924c89
3 changed files with 80 additions and 16 deletions
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49
src/pkg/go/printer/nodes.go
View File

@ -796,9 +796,15 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
p.funcBody(x.Body, distance(x.Type.Pos(), p.pos), true, multiLine)
case *ast.ParenExpr:
p.print(token.LPAREN)
p.expr0(x.X, reduceDepth(depth), multiLine) // parentheses undo one level of depth
p.print(x.Rparen, token.RPAREN)
if _, hasParens := x.X.(*ast.ParenExpr); hasParens {
// don't print parentheses around an already parenthesized expression
// TODO(gri) consider making this more general and incorporate precedence levels
p.expr0(x.X, reduceDepth(depth), multiLine) // parentheses undo one level of depth
} else {
p.print(token.LPAREN)
p.expr0(x.X, reduceDepth(depth), multiLine) // parentheses undo one level of depth
p.print(x.Rparen, token.RPAREN)
}
case *ast.SelectorExpr:
parts := selectorExprList(expr)
@ -969,16 +975,27 @@ func isTypeName(x ast.Expr) bool {
}
// TODO(gri): Decide if this should be used more broadly. The printing code
// knows when to insert parentheses for precedence reasons, but
// need to be careful to keep them around type expressions.
func stripParens(x ast.Expr, inControlClause bool) ast.Expr {
for px, hasParens := x.(*ast.ParenExpr); hasParens; px, hasParens = x.(*ast.ParenExpr) {
x = px.X
if cx, isCompositeLit := x.(*ast.CompositeLit); inControlClause && isCompositeLit && isTypeName(cx.Type) {
// composite literals inside control clauses need parens if they start with a type name;
// don't strip innermost layer
return px
func stripParens(x ast.Expr) ast.Expr {
if px, strip := x.(*ast.ParenExpr); strip {
// parentheses must not be stripped if there are any
// unparenthesized composite literals starting with
// a type name
ast.Inspect(px.X, func(node interface{}) bool {
switch x := node.(type) {
case *ast.ParenExpr:
// parentheses protect enclosed composite literals
return false
case *ast.CompositeLit:
if isTypeName(x.Type) {
strip = false // do not strip parentheses
}
return false
}
// in all other cases, keep inspecting
return true
})
if strip {
return stripParens(px.X)
}
}
return x
@ -991,7 +1008,7 @@ func (p *printer) controlClause(isForStmt bool, init ast.Stmt, expr ast.Expr, po
if init == nil && post == nil {
// no semicolons required
if expr != nil {
p.expr(stripParens(expr, true), ignoreMultiLine)
p.expr(stripParens(expr), ignoreMultiLine)
needsBlank = true
}
} else {
@ -1002,7 +1019,7 @@ func (p *printer) controlClause(isForStmt bool, init ast.Stmt, expr ast.Expr, po
}
p.print(token.SEMICOLON, blank)
if expr != nil {
p.expr(stripParens(expr, true), ignoreMultiLine)
p.expr(stripParens(expr), ignoreMultiLine)
needsBlank = true
}
if isForStmt {
@ -1183,7 +1200,7 @@ func (p *printer) stmt(stmt ast.Stmt, nextIsRBrace bool, multiLine *bool) {
p.expr(s.Value, multiLine)
}
p.print(blank, s.TokPos, s.Tok, blank, token.RANGE, blank)
p.expr(stripParens(s.X, true), multiLine)
p.expr(stripParens(s.X), multiLine)
p.print(blank)
p.block(s.Body, 1)
*multiLine = true

30
src/pkg/go/printer/testdata/statements.golden vendored
View File

@ -209,6 +209,36 @@ func _() {
for _ = range (T1{T{42}}) {
}
if x == (T{42}[0]) {
}
if (x == T{42}[0]) {
}
if x == (T{42}[0]) {
}
if x == (T{42}[0]) {
}
if x == (T{42}[0]) {
}
if x == a+b*(T{42}[0]) {
}
if (x == a+b*T{42}[0]) {
}
if x == a+b*(T{42}[0]) {
}
if x == a+(b * (T{42}[0])) {
}
if x == a+b*(T{42}[0]) {
}
if (a + b*(T{42}[0])) == x {
}
if (a + b*(T{42}[0])) == x {
}
if struct{ x bool }{false}.x {
}
if struct{ x bool }{false}.x == false {
}
}

17
src/pkg/go/printer/testdata/statements.input vendored
View File

@ -146,6 +146,23 @@ func _() {
switch ; ((((T{})))) {}
for _ = range (((T1{T{42}}))) {}
if x == (T{42}[0]) {}
if (x == T{42}[0]) {}
if (x == (T{42}[0])) {}
if (x == (((T{42}[0])))) {}
if (((x == (T{42}[0])))) {}
if x == a + b*(T{42}[0]) {}
if (x == a + b*T{42}[0]) {}
if (x == a + b*(T{42}[0])) {}
if (x == a + ((b * (T{42}[0])))) {}
if (((x == a + b * (T{42}[0])))) {}
if (((a + b * (T{42}[0])) == x)) {}
if (((a + b * (T{42}[0])))) == x {}
if (struct{x bool}{false}.x) {}
if (struct{x bool}{false}.x) == false {}
if (struct{x bool}{false}.x == false) {}
}