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Commit 583dac04 authored by Robert Griesemer's avatar Robert Griesemer
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- more cleanups (simpler code for optional semi's, bug fixes) 

R=r
OCL=16869
CL=16869
parent bbfe3123
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Showing with 73 additions and 94 deletions
usr/gri/pretty/parser.go
View file @ 583dac04
......@@ -15,10 +15,10 @@ export type Parser struct {
tokchan *<-chan *Scanner.Token;
// Scanner.Token
old int; // previous token
pos int; // token source position
tok int; // one token look-ahead
val string; // token value (for IDENT, NUMBER, STRING only)
semi bool; // true if a semicolon was inserted by the previous statement
// Nesting level
level int; // 0 = global scope, -1 = function scope of global functions, etc.
......@@ -54,13 +54,13 @@ func (P *Parser) Ecart() {
func (P *Parser) Next() {
P.old = P.tok;
if P.tokchan == nil {
P.pos, P.tok, P.val = P.scanner.Scan();
} else {
t := <-P.tokchan;
P.tok, P.pos, P.val = t.tok, t.pos, t.val;
}
P.semi = false;
if P.verbose {
P.PrintIndent();
print("[", P.pos, "] ", Scanner.TokenName(P.tok), "\n");
......@@ -73,7 +73,6 @@ func (P *Parser) Open(verbose bool, scanner *Scanner.Scanner, tokchan *<-chan *S
P.indent = 0;
P.scanner = scanner;
P.tokchan = tokchan;
P.old = Scanner.ILLEGAL;
P.Next();
P.level = 0;
}
......@@ -92,8 +91,8 @@ func (P *Parser) Expect(tok int) {
}
func (P *Parser) Optional(tok int) {
if P.tok == tok {
func (P *Parser) OptSemicolon() {
if P.tok == Scanner.SEMICOLON {
P.Next();
}
}
......@@ -115,22 +114,10 @@ func (P *Parser) CloseScope() {
func (P *Parser) TryType() (typ AST.Type, ok bool);
func (P *Parser) ParseExpression() AST.Expr;
func (P *Parser) TryStatement() (stat AST.Stat, ok bool);
func (P *Parser) ParseStatement() AST.Stat;
func (P *Parser) ParseDeclaration() AST.Node;
func (P *Parser) OptSemicolon(tok int) {
P.Trace("OptSemicolon");
if P.tok == Scanner.SEMICOLON {
P.Next();
} else if P.level != 0 || P.old != tok || P.tok != tok {
// TODO FIX THIS
// P.Expect(Scanner.SEMICOLON);
}
P.Ecart();
}
func (P *Parser) ParseIdent() *AST.Ident {
P.Trace("Ident");
......@@ -454,7 +441,7 @@ func (P *Parser) ParseStructType() *AST.StructType {
P.Expect(Scanner.SEMICOLON);
}
}
P.Optional(Scanner.SEMICOLON);
P.OptSemicolon();
P.Expect(Scanner.RBRACE);
}
......@@ -503,31 +490,16 @@ func (P *Parser) TryType() (typ_ AST.Type, ok_ bool) {
// ----------------------------------------------------------------------------
// Blocks
func (P *Parser) ParseStatement() AST.Stat {
P.Trace("Statement");
stat, ok := P.TryStatement();
if ok {
P.OptSemicolon(Scanner.RBRACE);
} else {
P.Error(P.pos, "statement expected");
P.Next(); // make progress
}
P.Ecart();
return stat;
}
func (P *Parser) ParseStatementList() *AST.List {
P.Trace("StatementList");
stats := AST.NewList();
for {
stat, ok := P.TryStatement();
if ok {
stats.Add(stat);
P.Optional(Scanner.SEMICOLON);
for P.tok != Scanner.CASE && P.tok != Scanner.DEFAULT && P.tok != Scanner.RBRACE && P.tok != Scanner.EOF {
stats.Add(P.ParseStatement());
if P.tok == Scanner.SEMICOLON {
P.Next();
} else if P.semi {
P.semi = false; // consume inserted ";"
} else {
break;
}
......@@ -546,13 +518,13 @@ func (P *Parser) ParseBlock() *AST.Block {
P.Expect(Scanner.LBRACE);
P.OpenScope();
if P.tok != Scanner.RBRACE && P.tok != Scanner.SEMICOLON {
if P.tok != Scanner.RBRACE {
block.stats = P.ParseStatementList();
}
P.Optional(Scanner.SEMICOLON);
P.OptSemicolon();
P.CloseScope();
P.Expect(Scanner.RBRACE);
P.semi = true; // allow optional semicolon
P.Ecart();
return block;
......@@ -801,14 +773,15 @@ func (P *Parser) ParsePrimaryExpr() AST.Expr {
P.Trace("PrimaryExpr");
x := P.ParseOperand();
L: for {
for {
switch P.tok {
case Scanner.PERIOD: x = P.ParseSelectorOrTypeGuard(x);
case Scanner.LBRACK: x = P.ParseIndexOrSlice(x);
case Scanner.LPAREN: x = P.ParseCall(x);
default: break L;
default: goto exit;
}
}
exit:
P.Ecart();
return x;
......@@ -899,6 +872,7 @@ func (P *Parser) ParseSimpleStat() AST.Stat {
l.ident = AST.NIL;
}
P.Next(); // consume ":"
P.semi = true; // allow optional semicolon
stat = l;
case
......@@ -1083,14 +1057,8 @@ func (P *Parser) ParseCaseClause() *AST.CaseClause {
P.Trace("CaseClause");
clause := P.ParseCase();
if P.tok != Scanner.FALLTHROUGH && P.tok != Scanner.RBRACE {
if P.tok != Scanner.CASE && P.tok != Scanner.DEFAULT && P.tok != Scanner.RBRACE {
clause.stats = P.ParseStatementList();
P.Optional(Scanner.SEMICOLON);
}
if P.tok == Scanner.FALLTHROUGH {
P.Next();
clause.falls = true;
P.Optional(Scanner.SEMICOLON);
}
P.Ecart();
......@@ -1107,10 +1075,11 @@ func (P *Parser) ParseSwitchStat() *AST.SwitchStat {
stat.cases = AST.NewList();
P.Expect(Scanner.LBRACE);
for P.tok == Scanner.CASE || P.tok == Scanner.DEFAULT {
for P.tok != Scanner.RBRACE && P.tok != Scanner.EOF {
stat.cases.Add(P.ParseCaseClause());
}
P.Expect(Scanner.RBRACE);
P.semi = true; // allow optional semicolon
P.Ecart();
return stat;
......@@ -1121,20 +1090,11 @@ func (P *Parser) ParseCommCase() {
P.Trace("CommCase");
if P.tok == Scanner.CASE {
P.Next();
if P.tok == Scanner.GTR {
// send
P.Next();
P.ParseExpression();
P.Expect(Scanner.EQL);
P.ParseExpression();
} else {
// receive
if P.tok != Scanner.LSS {
P.ParseIdent();
P.Expect(Scanner.ASSIGN);
}
P.Expect(Scanner.LSS);
if P.tok == Scanner.ASSIGN || P.tok == Scanner.DEFINE {
P.Next();
P.Expect(Scanner.ARROW);
P.ParseExpression();
}
} else {
......@@ -1152,26 +1112,12 @@ func (P *Parser) ParseCommClause() {
P.ParseCommCase();
if P.tok != Scanner.CASE && P.tok != Scanner.DEFAULT && P.tok != Scanner.RBRACE {
P.ParseStatementList();
P.Optional(Scanner.SEMICOLON);
}
P.Ecart();
}
func (P *Parser) ParseRangeStat() {
P.Trace("RangeStat");
P.Expect(Scanner.RANGE);
P.ParseIdentList();
P.Expect(Scanner.DEFINE);
P.ParseExpression();
P.ParseBlock();
P.Ecart();
}
func (P *Parser) ParseSelectStat() {
P.Trace("SelectStat");
......@@ -1180,18 +1126,46 @@ func (P *Parser) ParseSelectStat() {
for P.tok != Scanner.RBRACE && P.tok != Scanner.EOF {
P.ParseCommClause();
}
P.Next();
P.Expect(Scanner.RBRACE);
P.semi = true; // allow optional semicolon
P.Ecart();
}
func (P *Parser) ParseFallthroughStat() {
P.Trace("FallthroughStat");
P.Expect(Scanner.FALLTHROUGH);
P.Ecart();
}
func (P *Parser) TryStatement() (stat_ AST.Stat, ok_ bool) {
P.Trace("Statement (try)");
func (P *Parser) ParseEmptyStat() {
P.Trace("EmptyStat");
P.Ecart();
}
func (P *Parser) ParseRangeStat() {
P.Trace("RangeStat");
P.Expect(Scanner.RANGE);
P.ParseIdentList();
P.Expect(Scanner.DEFINE);
P.ParseExpression();
P.ParseBlock();
P.Ecart();;
}
func (P *Parser) ParseStatement() AST.Stat {
P.Trace("Statement");
indent := P.indent;
var stat AST.Stat = AST.NIL;
res := true;
switch P.tok {
case Scanner.CONST, Scanner.TYPE, Scanner.VAR:
stat = P.ParseDeclaration();
......@@ -1218,16 +1192,17 @@ func (P *Parser) TryStatement() (stat_ AST.Stat, ok_ bool) {
P.ParseRangeStat();
case Scanner.SELECT:
P.ParseSelectStat();
case Scanner.FALLTHROUGH:
P.ParseFallthroughStat();
default:
// no statement found
res = false;
P.ParseEmptyStat(); // for complete tracing output only
}
if indent != P.indent {
panic("imbalanced tracing code (Statement)");
}
P.Ecart();
return stat, res;
return stat;
}
......@@ -1284,6 +1259,7 @@ func (P *Parser) ParseTypeSpec(exported bool) *AST.TypeDecl {
decl := new(AST.TypeDecl);
decl.ident = P.ParseIdent();
decl.typ = P.ParseType();
P.semi = true; // allow optional semicolon
P.Ecart();
return decl;
......@@ -1335,13 +1311,17 @@ func (P *Parser) ParseDecl(exported bool, keyword int) *AST.Declaration {
P.Expect(keyword);
if P.tok == Scanner.LPAREN {
P.Next();
for P.tok != Scanner.RPAREN && P.tok != Scanner.EOF {
decl.decls.Add(P.ParseSpec(exported, keyword));
P.OptSemicolon(Scanner.RPAREN);
for P.tok != Scanner.RPAREN {
decl.decls.Add(P.ParseSpec(exported, keyword));
P.OptSemicolon(Scanner.RPAREN);
if P.tok == Scanner.SEMICOLON {
P.Next();
} else {
break;
}
}
P.Next(); // consume ")"
P.Expect(Scanner.RPAREN);
P.semi = true; // allow optional semicolon
} else {
decl.decls.Add(P.ParseSpec(exported, keyword));
}
......@@ -1462,8 +1442,6 @@ func (P *Parser) ParseDeclaration() AST.Node {
}
}
P.OptSemicolon(Scanner.RBRACE);
if indent != P.indent {
panic("imbalanced tracing code (Declaration)");
}
......@@ -1491,11 +1469,12 @@ func (P *Parser) ParseProgram() *AST.Program {
for P.tok == Scanner.IMPORT {
decls.Add(P.ParseDecl(false, Scanner.IMPORT));
P.Optional(Scanner.SEMICOLON);
P.OptSemicolon();
}
for P.tok != Scanner.EOF {
decls.Add(P.ParseDeclaration());
P.OptSemicolon();
}
if P.level != 0 {
......
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