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go/parser: better error messages for if/switch/for conditions/expressions

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Fixes #7102.

LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/56770045
This commit is contained in:
Robert Griesemer 2014-02-11 16:45:31 -08:00
parent ba5594742d
commit 947aaf275c
2 changed files with 15 additions and 11 deletions
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10
src/pkg/go/parser/parser.go
View File

@ -1762,14 +1762,14 @@ func (p *parser) parseBranchStmt(tok token.Token) *ast.BranchStmt {
return &ast.BranchStmt{TokPos: pos, Tok: tok, Label: label}
}
func (p *parser) makeExpr(s ast.Stmt) ast.Expr {
func (p *parser) makeExpr(s ast.Stmt, kind string) ast.Expr {
if s == nil {
return nil
}
if es, isExpr := s.(*ast.ExprStmt); isExpr {
return p.checkExpr(es.X)
}
p.error(s.Pos(), "expected condition, found simple statement (missing parentheses around composite literal?)")
p.error(s.Pos(), fmt.Sprintf("expected %s, found simple statement (missing parentheses around composite literal?)", kind))
return &ast.BadExpr{From: s.Pos(), To: s.End()}
}
@ -1796,7 +1796,7 @@ func (p *parser) parseIfStmt() *ast.IfStmt {
p.next()
x = p.parseRhs()
} else {
x = p.makeExpr(s)
x = p.makeExpr(s, "boolean expression")
s = nil
}
}
@ -1927,7 +1927,7 @@ func (p *parser) parseSwitchStmt() ast.Stmt {
return &ast.TypeSwitchStmt{Switch: pos, Init: s1, Assign: s2, Body: body}
}
return &ast.SwitchStmt{Switch: pos, Init: s1, Tag: p.makeExpr(s2), Body: body}
return &ast.SwitchStmt{Switch: pos, Init: s1, Tag: p.makeExpr(s2, "switch expression"), Body: body}
}
func (p *parser) parseCommClause() *ast.CommClause {
@ -2072,7 +2072,7 @@ func (p *parser) parseForStmt() ast.Stmt {
return &ast.ForStmt{
For: pos,
Init: s1,
Cond: p.makeExpr(s2),
Cond: p.makeExpr(s2, "boolean or range expression"),
Post: s3,
Body: body,
}

16
src/pkg/go/parser/short_test.go
View File

@ -48,14 +48,14 @@ var invalids = []string{
`package p; func f() { if { /* ERROR "expected operand" */ } };`,
`package p; func f() { if ; { /* ERROR "expected operand" */ } };`,
`package p; func f() { if f(); { /* ERROR "expected operand" */ } };`,
`package p; func f() { if _ /* ERROR "expected condition" */ = range x; true {} };`,
`package p; func f() { switch _ /* ERROR "expected condition" */ = range x; true {} };`,
`package p; func f() { if _ /* ERROR "expected boolean expression" */ = range x; true {} };`,
`package p; func f() { switch _ /* ERROR "expected switch expression" */ = range x; true {} };`,
`package p; func f() { for _ = range x ; /* ERROR "expected '{'" */ ; {} };`,
`package p; func f() { for ; ; _ = range /* ERROR "expected operand" */ x {} };`,
`package p; func f() { for ; _ /* ERROR "expected condition" */ = range x ; {} };`,
`package p; func f() { switch t /* ERROR "expected condition" */ = t.(type) {} };`,
`package p; func f() { switch t /* ERROR "expected condition" */ , t = t.(type) {} };`,
`package p; func f() { switch t /* ERROR "expected condition" */ = t.(type), t {} };`,
`package p; func f() { for ; _ /* ERROR "expected boolean or range expression" */ = range x ; {} };`,
`package p; func f() { switch t /* ERROR "expected switch expression" */ = t.(type) {} };`,
`package p; func f() { switch t /* ERROR "expected switch expression" */ , t = t.(type) {} };`,
`package p; func f() { switch t /* ERROR "expected switch expression" */ = t.(type), t {} };`,
`package p; var a = [ /* ERROR "expected expression" */ 1]int;`,
`package p; var a = [ /* ERROR "expected expression" */ ...]int;`,
`package p; var a = struct /* ERROR "expected expression" */ {}`,
@ -82,6 +82,10 @@ var invalids = []string{
`package p; func f() { var s []int; _ = s[: /* ERROR "2nd index required" */ :] };`,
`package p; func f() { var s []int; _ = s[: /* ERROR "2nd index required" */ ::] };`,
`package p; func f() { var s []int; _ = s[i:j:k: /* ERROR "expected ']'" */ l] };`,
`package p; func f() { for x /* ERROR "boolean or range expression" */ = []string {} }`,
`package p; func f() { for x /* ERROR "boolean or range expression" */ := []string {} }`,
`package p; func f() { for i /* ERROR "boolean or range expression" */ , x = []string {} }`,
`package p; func f() { for i /* ERROR "boolean or range expression" */ , x := []string {} }`,
}
func TestInvalid(t *testing.T) {