gc: improved syntax errors
* example-based syntax errors (go.errors)
* enable bison's more specific errors
and translate grammar token names into
tokens like ++
* test cases
R=ken2, r, ken3
CC=golang-dev
https://golang.org/cl/194085
diff --git a/src/cmd/gc/Makefile b/src/cmd/gc/Makefile
index 99dbd51..16bfc66 100644
--- a/src/cmd/gc/Makefile
+++ b/src/cmd/gc/Makefile
@@ -41,7 +41,7 @@
typecheck.$O\
unsafe.$O\
walk.$O\
- y.tab.$O\
+ y1.tab.$O\
$(LIB): $(OFILES)
ar rsc $(LIB) $(OFILES)
@@ -49,11 +49,19 @@
$(OFILES): $(HFILES)
y.tab.h: $(YFILES)
- bison -y $(YFLAGS) $(YFILES)
+ bison -v -y $(YFLAGS) $(YFILES)
y.tab.c: y.tab.h
test -f y.tab.c && touch y.tab.c
+y1.tab.c: y.tab.c # make yystate global, yytname mutable
+ cat y.tab.c | sed '/ int yystate;/d; s/int yychar;/int yychar, yystate;/; s/static const char \*const yytname/const char *yytname/' >y1.tab.c
+
+yerr.h: bisonerrors go.errors y.tab.h # y.tab.h rule generates y.output too
+ awk -f bisonerrors y.output go.errors >yerr.h
+
+subr.$O: yerr.h
+
builtin.c: builtin.c.boot
cp builtin.c.boot builtin.c
@@ -63,6 +71,6 @@
./mkopnames go.h >opnames.h
clean:
- rm -f *.[568o] enam.c [568].out a.out y.tab.h y.tab.c $(LIB) mkbuiltin1 builtin.c _builtin.c opnames.h
+ rm -f *.[568o] enam.c [568].out a.out y.tab.h y.tab.c y1.tab.c y.output yerr.h $(LIB) mkbuiltin1 builtin.c _builtin.c opnames.h
install: $(LIB)
diff --git a/src/cmd/gc/bisonerrors b/src/cmd/gc/bisonerrors
new file mode 100755
index 0000000..5110f53
--- /dev/null
+++ b/src/cmd/gc/bisonerrors
@@ -0,0 +1,124 @@
+#!/usr/bin/awk -f
+# Copyright 2010 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+# This program implements the core idea from
+#
+# Clinton L. Jeffery, Generating LR syntax error messages from examples,
+# ACM TOPLAS 25(5) (September 2003). http://doi.acm.org/10.1145/937563.937566
+#
+# It reads Bison's summary of a grammar followed by a file
+# like go.errors, replacing lines beginning with % by the
+# yystate and yychar that will be active when an error happens
+# while parsing that line.
+#
+# Unlike the system described in the paper, the lines in go.errors
+# give grammar symbol name lists, not actual program fragments.
+# This is a little less programmer-friendly but doesn't require being
+# able to run the text through lex.c.
+
+BEGIN{
+ bison = 1
+ grammar = 0
+ states = 0
+}
+
+# In Grammar section of y.output,
+# record lhs and length of rhs for each rule.
+bison && /^Grammar/ { grammar = 1 }
+bison && /^(Terminals|state 0)/ { grammar = 0 }
+grammar && NF>0 {
+ if($2 != "|") {
+ r = $2
+ sub(/:$/, "", r)
+ }
+ rulelhs[$1] = r
+ rulesize[$1] = NF-2
+ if(rulesize[$1] == 3 && $3 $4 $5 == "/*empty*/") {
+ rulesize[$1] = 0
+ }
+}
+
+# In state dumps, record shift/reduce actions.
+bison && /^state 0/ { grammar = 0; states = 1 }
+
+states && /^state / { state = $2 }
+states { statetext[state] = statetext[state] $0 "\n" }
+
+states && / shift, and go to state/ {
+ n = nshift[state]++
+ shift[state,n] = $7
+ shifttoken[state,n] = $1
+ next
+}
+states && / go to state/ {
+ n = nshift[state]++
+ shift[state,n] = $5
+ shifttoken[state,n] = $1
+ next
+}
+states && / reduce using rule/ {
+ n = nreduce[state]++
+ reduce[state,n] = $5
+ reducetoken[state,n] = $1
+ next
+}
+
+# First // comment marks the beginning of the pattern file.
+/^\/\// { bison = 0; grammar = 0; state = 0 }
+bison { next }
+
+# Treat % as first field on line as introducing a pattern (token sequence).
+# Run it through the LR machine and print the induced "yystate, yychar,"
+# at the point where the error happens.
+$1 == "%" {
+ nstack = 0
+ state = 0
+ f = 2
+ tok = ""
+ for(;;) {
+ if(tok == "" && f <= NF) {
+ tok = $f
+ f++
+ }
+ found = 0
+ for(j=0; j<nshift[state]; j++) {
+ if(shifttoken[state,j] == tok) {
+ # print "SHIFT " tok " " state " -> " shift[state,j]
+ stack[nstack++] = state
+ state = shift[state,j]
+ found = 1
+ tok = ""
+ break
+ }
+ }
+ if(found)
+ continue
+ for(j=0; j<nreduce[state]; j++) {
+ if(reducetoken[state,j] == tok || reducetoken[state,j] == "$default") {
+ stack[nstack++] = state
+ rule = reduce[state,j]
+ nstack -= rulesize[rule]
+ state = stack[--nstack]
+ lhs = rulelhs[rule]
+ if(tok != "")
+ --f
+ tok = rulelhs[rule]
+ # print "REDUCE " nstack " " state " " tok " rule " rule " size " rulesize[rule]
+ found = 1
+ break
+ }
+ }
+ if(found)
+ continue
+
+ # No shift or reduce applied - found the error.
+ printf("\t%s, %s,\n", state, tok);
+ break
+ }
+ next
+}
+
+# Print other lines verbatim.
+{print}
diff --git a/src/cmd/gc/go.errors b/src/cmd/gc/go.errors
new file mode 100644
index 0000000..215f28c
--- /dev/null
+++ b/src/cmd/gc/go.errors
@@ -0,0 +1,46 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Example-based syntax error messages.
+// See bisonerrors, Makefile, go.y.
+
+static struct {
+ int yystate;
+ int yychar;
+ char *msg;
+} yymsg[] = {
+ // Each line of the form % token list
+ // is converted by bisonerrors into the yystate and yychar caused
+ // by that token list.
+
+ % loadsys package LIMPORT '(' LLITERAL import_package import_there ','
+ "unexpected , during import block",
+
+ % loadsys package imports LFUNC LNAME '(' ')' '{' LIF if_header ';'
+ "unexpected ; or newline before {",
+
+ % loadsys package imports LFUNC LNAME '(' ')' '{' LSWITCH if_header ';'
+ "unexpected ; or newline before {",
+
+ % loadsys package imports LFUNC LNAME '(' ')' '{' LFOR for_header ';'
+ "unexpected ; or newline before {",
+
+ % loadsys package imports LFUNC LNAME '(' ')' '{' LFOR ';' LBODY
+ "unexpected ; or newline before {",
+
+ % loadsys package imports LFUNC LNAME '(' ')' ';' '{'
+ "unexpected ; or newline before {",
+
+ % loadsys package imports LTYPE LNAME ';'
+ "unexpected ; or newline in type declaration",
+
+ % loadsys package imports LFUNC LNAME '(' ')' '{' if_stmt ';' LELSE
+ "unexpected ; or newline before else",
+
+ % loadsys package imports LTYPE LNAME LINTERFACE '{' LNAME ',' LNAME
+ "name list not allowed in interface type",
+
+ % loadsys package imports LFUNC LNAME '(' ')' '{' LFOR LVAR LNAME '=' LNAME
+ "var declaration not allowed in for initializer",
+};
diff --git a/src/cmd/gc/go.y b/src/cmd/gc/go.y
index db9b0db..c309d0d 100644
--- a/src/cmd/gc/go.y
+++ b/src/cmd/gc/go.y
@@ -36,13 +36,12 @@
%token <lint> LASOP
%token <sym> LBREAK LCASE LCHAN LCOLAS LCONST LCONTINUE LDDD
%token <sym> LDEFAULT LDEFER LELSE LFALL LFOR LFUNC LGO LGOTO
-%token <sym> LIF LIMPORT LINTERFACE LMAKE LMAP LNAME LNEW
+%token <sym> LIF LIMPORT LINTERFACE LMAP LNAME
%token <sym> LPACKAGE LRANGE LRETURN LSELECT LSTRUCT LSWITCH
%token <sym> LTYPE LVAR
%token LANDAND LANDNOT LBODY LCOMM LDEC LEQ LGE LGT
%token LIGNORE LINC LLE LLSH LLT LNE LOROR LRSH
-%token LSEMIBRACE
%type <lint> lbrace import_here
%type <sym> sym packname
@@ -112,6 +111,8 @@
%left ')'
%left PreferToRightParen
+%error-verbose
+
%%
file:
loadsys
@@ -800,12 +801,12 @@
{
$$ = nod(OINDEX, $1, $3);
}
-| pexpr '[' expr ':' ']'
+| pexpr '[' oexpr ':' oexpr ']'
{
- $$ = nod(OSLICE, $1, nod(OKEY, $3, N));
- }
-| pexpr '[' expr ':' expr ']'
- {
+ if($3 == N) {
+ yyerror("missing lower bound in slice expression");
+ $3 = nodintconst(0);
+ }
$$ = nod(OSLICE, $1, nod(OKEY, $3, $5));
}
| pseudocall
diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index 8d67b8b..4d74bb9 100644
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -9,6 +9,8 @@
extern int yychar;
void lexfini(void);
+void yytinit(void);
+
static char *goos, *goarch, *goroot;
#define DBG if(!debug['x']);else print
@@ -92,6 +94,7 @@
lexinit();
typeinit();
+ yytinit();
blockgen = 1;
dclcontext = PEXTERN;
@@ -1469,6 +1472,87 @@
return buf;
}
+struct
+{
+ char *have;
+ char *want;
+} yytfix[] =
+{
+ "$end", "EOF",
+ "LLITERAL", "literal",
+ "LASOP", "op=",
+ "LBREAK", "break",
+ "LCASE", "case",
+ "LCOLAS", ":=",
+ "LCONST", "const",
+ "LCONTINUE", "continue",
+ "LDDD", "...",
+ "LDEFAULT", "default",
+ "LDEFER", "defer",
+ "LELSE", "else",
+ "LFALL", "fallthrough",
+ "LFOR", "for",
+ "LFUNC", "func",
+ "LGO", "go",
+ "LGOTO", "goto",
+ "LIF", "if",
+ "LIMPORT", "import",
+ "LINTERFACE", "interface",
+ "LMAP", "map",
+ "LNAME", "name",
+ "LPACKAGE", "package",
+ "LRANGE", "range",
+ "LRETURN", "return",
+ "LSELECT", "select",
+ "LSTRUCT", "struct",
+ "LSWITCH", "switch",
+ "LTYPE", "type",
+ "LVAR", "var",
+ "LANDAND", "&&",
+ "LANDNOT", "&^",
+ "LBODY", "{",
+ "LCOMM", "<-",
+ "LDEC", "--",
+ "LINC", "++",
+ "LEQ", "==",
+ "LGE", ">=",
+ "LGT", ">",
+ "LLE", "<=",
+ "LLT", "<",
+ "LLSH", "<<",
+ "LRSH", ">>",
+ "LOROR", "||",
+ "LNE", "!=",
+};
+
+void
+yytinit(void)
+{
+ int i, j;
+ extern char *yytname[];
+ char *s, *t;
+
+ for(i=0; yytname[i] != nil; i++) {
+ s = yytname[i];
+
+ // turn 'x' into x.
+ if(s[0] == '\'') {
+ t = strdup(s+1);
+ t[strlen(t)-1] = '\0';
+ yytname[i] = t;
+ continue;
+ }
+
+ // apply yytfix to the rest
+ for(j=0; j<nelem(yytfix); j++) {
+ if(strcmp(s, yytfix[j].have) == 0) {
+ yytname[i] = yytfix[j].want;
+ break;
+ }
+ }
+ }
+}
+
void
mkpackage(char* pkgname)
{
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index 74ca4cc..9d0c84a 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -6,6 +6,7 @@
#include "md5.h"
#include "y.tab.h"
#include "opnames.h"
+#include "yerr.h"
typedef struct Error Error;
struct Error
@@ -120,14 +121,47 @@
fatal("too many errors");
}
+extern int yystate, yychar;
+
void
yyerror(char *fmt, ...)
{
+ int i;
+ static int lastsyntax;
va_list arg;
- if(strcmp(fmt, "syntax error") == 0) {
- yyerrorl(lexlineno, "syntax error near %s", lexbuf);
+ if(strncmp(fmt, "syntax error", 12) == 0) {
nsyntaxerrors++;
+
+ if(debug['x'])
+ print("yyerror: yystate=%d yychar=%d\n", yystate, yychar);
+
+ // only one syntax error per line
+ if(lastsyntax == lexlineno)
+ return;
+ lastsyntax = lexlineno;
+
+ // look for parse state-specific errors in list (see go.errors).
+ for(i=0; i<nelem(yymsg); i++) {
+ if(yymsg[i].yystate == yystate && yymsg[i].yychar == yychar) {
+ yyerrorl(lexlineno, "syntax error: %s", yymsg[i].msg);
+ return;
+ }
+ }
+
+ // plain "syntax error" gets "near foo" added
+ if(strcmp(fmt, "syntax error") == 0) {
+ yyerrorl(lexlineno, "syntax error near %s", lexbuf);
+ return;
+ }
+
+ // if bison says "syntax error, more info"; print "syntax error: more info".
+ if(fmt[12] == ',') {
+ yyerrorl(lexlineno, "syntax error:%s", fmt+13);
+ return;
+ }
+
+ yyerrorl(lexlineno, "%s", fmt);
return;
}
diff --git a/test/golden.out b/test/golden.out
index d87842e..59a83e7 100644
--- a/test/golden.out
+++ b/test/golden.out
@@ -97,6 +97,8 @@
== nilptr/
+== syntax/
+
== fixedbugs/
=========== fixedbugs/bug016.go
diff --git a/test/run b/test/run
index b9bc5da0..6d9a71f 100755
--- a/test/run
+++ b/test/run
@@ -48,7 +48,7 @@
true >pass.out >times.out
-for dir in . ken chan interface nilptr fixedbugs bugs
+for dir in . ken chan interface nilptr syntax fixedbugs bugs
do
echo
echo '==' $dir'/'
diff --git a/test/syntax/forvar.go b/test/syntax/forvar.go
new file mode 100644
index 0000000..f12ce55
--- /dev/null
+++ b/test/syntax/forvar.go
@@ -0,0 +1,10 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+ for var x = 0; x < 10; x++ { // ERROR "var declaration not allowed in for initializer"
diff --git a/test/syntax/import.go b/test/syntax/import.go
new file mode 100644
index 0000000..90e7df0
--- /dev/null
+++ b/test/syntax/import.go
@@ -0,0 +1,14 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+ "io", // ERROR "unexpected ,"
+ "os"
+)
+
+
diff --git a/test/syntax/interface.go b/test/syntax/interface.go
new file mode 100644
index 0000000..a7f4353
--- /dev/null
+++ b/test/syntax/interface.go
@@ -0,0 +1,14 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type T interface {
+ f, g () // ERROR "name list not allowed in interface type"
+}
+
+
+
diff --git a/test/syntax/semi1.go b/test/syntax/semi1.go
new file mode 100644
index 0000000..c805bb0
--- /dev/null
+++ b/test/syntax/semi1.go
@@ -0,0 +1,14 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+ if x; y // ERROR "unexpected ; or newline before {"
+ {
+ z
+
+
diff --git a/test/syntax/semi2.go b/test/syntax/semi2.go
new file mode 100644
index 0000000..237fac8
--- /dev/null
+++ b/test/syntax/semi2.go
@@ -0,0 +1,14 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+ switch x; y // ERROR "unexpected ; or newline before {"
+ {
+ z
+
+
diff --git a/test/syntax/semi3.go b/test/syntax/semi3.go
new file mode 100644
index 0000000..2dbcb59
--- /dev/null
+++ b/test/syntax/semi3.go
@@ -0,0 +1,14 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+ for x; y; z // ERROR "unexpected ; or newline before {"
+ {
+ z
+
+
diff --git a/test/syntax/semi4.go b/test/syntax/semi4.go
new file mode 100644
index 0000000..2268cf7
--- /dev/null
+++ b/test/syntax/semi4.go
@@ -0,0 +1,14 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+ for x
+ { // ERROR "unexpected ; or newline before {"
+ z
+
+
diff --git a/test/syntax/semi5.go b/test/syntax/semi5.go
new file mode 100644
index 0000000..7f907fb
--- /dev/null
+++ b/test/syntax/semi5.go
@@ -0,0 +1,13 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main()
+{ // ERROR "unexpected ; or newline before {"
+
+
+
diff --git a/test/syntax/semi6.go b/test/syntax/semi6.go
new file mode 100644
index 0000000..75de3e0
--- /dev/null
+++ b/test/syntax/semi6.go
@@ -0,0 +1,13 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type T // ERROR "unexpected ; or newline in type declaration"
+{
+
+
+
diff --git a/test/syntax/semi7.go b/test/syntax/semi7.go
new file mode 100644
index 0000000..4589043
--- /dev/null
+++ b/test/syntax/semi7.go
@@ -0,0 +1,14 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+ if x { }
+ else { } // ERROR "unexpected ; or newline before else"
+}
+
+
diff --git a/test/syntax/slice.go b/test/syntax/slice.go
new file mode 100644
index 0000000..4bc5d4d
--- /dev/null
+++ b/test/syntax/slice.go
@@ -0,0 +1,9 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var x = y[:z] // ERROR "missing lower bound in slice expression"
