- Use "expected X" rather then "expecting X".
- Report a better error when a type argument list is expected.
- Adjust various tests.
For #54511.
Change-Id: I0c5ca66ecbbdcae1a8f67377682aae6b0b6ab89a
Reviewed-on: https://go-review.googlesource.com/c/go/+/425734
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
For syntax errors in various (syntactic) lists, instead of reporting
a set of "expected" tokens (which may be incomplete), provide context
and mention "possibly missing" tokens. The result is a friendlier and
more accurate error message.
Fixes#49205.
Change-Id: I38ae7bf62febfe790075e62deb33ec8c17d64476
Reviewed-on: https://go-review.googlesource.com/c/go/+/396914
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The exact same test case covered by this file is also in
fixedbugs/bug121.go. No need for duplication.
Also, the actual syntax error tested (multiple method names
with a single signature) is an unlikely syntax error, and
only here for historical reasons (in the very beginning, this
was actually possible to write). Now, virtually nobody is making
this mistake.
Change-Id: I9d68e0aee2a63025f44e6338647f8250ecc3077a
Reviewed-on: https://go-review.googlesource.com/c/go/+/307789
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The gofrontend code doesn't distinguish semicolon and newline,
and it doesn't have special treatment for EOF.
syntax/semi6.go:9:47: error: unexpected semicolon or newline in type declaration
syntax/semi6.go:11:62: error: unexpected semicolon or newline in type declaration
Change-Id: I9996b59a4fc78ad1935e779f354ddf75c0fb44e0
Reviewed-on: https://go-review.googlesource.com/c/go/+/274692
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
This matches the error messages after CL 273890.
syntax/semi4.go:11:9: error: unexpected semicolon or newline, expecting ‘{’ after for clause
syntax/semi4.go:10:13: error: reference to undefined name ‘x’
syntax/semi4.go:12:17: error: reference to undefined name ‘z’
Change-Id: Ic88ff6e27d50bf70f5b2114383b84c42c0682f39
Reviewed-on: https://go-review.googlesource.com/c/go/+/273891
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
These changes match the following gofrontend error messages:
blank1.go:16:1: error: may not define methods on non-local type
chan/perm.go:28:9: error: expected channel
chan/perm.go:29:11: error: left operand of ‘<-’ must be channel
chan/perm.go:69:9: error: argument must be channel
complit1.go:25:16: error: attempt to slice object that is not array, slice, or string
complit1.go:26:16: error: attempt to slice object that is not array, slice, or string
complit1.go:27:17: error: attempt to slice object that is not array, slice, or string
complit1.go:49:41: error: may only omit types within composite literals of slice, array, or map type
complit1.go:50:14: error: expected struct, slice, array, or map type for composite literal
convlit.go:24:9: error: invalid type conversion (cannot use type unsafe.Pointer as type string)
convlit.go:25:9: error: invalid type conversion (cannot use type unsafe.Pointer as type float64)
convlit.go:26:9: error: invalid type conversion (cannot use type unsafe.Pointer as type int)
ddd1.go:63:9: error: invalid use of ‘...’ calling non-variadic function
fixedbugs/bug176.go:12:18: error: index expression is not integer constant
fixedbugs/bug332.go:17:10: error: use of undefined type ‘T’
fixedbugs/issue4232.go:22:16: error: integer constant overflow
fixedbugs/issue4232.go:33:16: error: integer constant overflow
fixedbugs/issue4232.go:44:25: error: integer constant overflow
fixedbugs/issue4232.go:55:16: error: integer constant overflow
fixedbugs/issue4458.go:19:14: error: type has no method ‘foo’
fixedbugs/issue5172.go:24:14: error: too many expressions for struct
init.go:17:9: error: reference to undefined name ‘runtime’
initializerr.go:26:29: error: duplicate value for index 1
interface/explicit.go:60:14: error: type assertion only valid for interface types
label.go:64:9: error: reference to undefined label ‘go2’
label1.go:18:97: error: continue statement not within for
label1.go:22:97: error: continue statement not within for
label1.go:106:89: error: continue statement not within for
label1.go:108:26: error: invalid continue label ‘on’
label1.go:111:118: error: break statement not within for or switch or select
label1.go:113:23: error: invalid break label ‘dance’
map1.go:64:9: error: not enough arguments
map1.go:65:9: error: not enough arguments
map1.go:67:9: error: argument 1 must be a map
method2.go:36:11: error: reference to undefined field or method ‘val’
method2.go:37:11: error: reference to undefined field or method ‘val’
method2.go:41:12: error: method requires pointer (use ‘(*T).g’)
syntax/chan1.go:13:19: error: send statement used as value; use select for non-blocking send
syntax/chan1.go:17:11: error: send statement used as value; use select for non-blocking send
Change-Id: I98047b60a376e3d2788836300f7fcac3f2c285cb
Reviewed-on: https://go-review.googlesource.com/c/go/+/273527
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
The error message is now positioned at the statement position (which is
an identifing token, such as the '=' for assignments); and in case of
assignments it emphasizes the assignment by putting the Lhs and Rhs
in parentheses. Finally, the wording is changed from "use of * as value"
to the stronger "cannot use * as value" (for which there is precedent
elsewhere in the parser).
Fixes#36858.
Change-Id: Ic3f101bba50f58e3a1d9b29645066634631f2d61
Reviewed-on: https://go-review.googlesource.com/c/go/+/218337
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Don't report errors if we don't have a correct type switch
guard; instead ignore it and leave it to the type-checker
to report the error. This leads to better error messages
concentrating on the type switch guard rather than errors
around (confusing) syntactic details.
Also clean up some code setting up AssertExpr (they never
have a nil Type field) and remove some incorrect TODOs.
Fixes#24470.
Change-Id: I69512f36e0417e3b5ea9c8856768e04b19d654a8
Reviewed-on: https://go-review.googlesource.com/103615
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
The new syntax tree introduced with 1.8 represents send statements
(ch <- x) as statements; the old syntax tree represented them as
expressions (and parsed them as such) but complained if they were
used in expression context. As a consequence, some of the errors
that in the past were of the form "ch <- x used as value" now look
like "unexpected <- ..." because a "<-" is not valid according to
Go syntax in those situations. Accept the new error message.
Also: Fine-tune handling of misformed for loop headers.
Also: Minor cleanups/better comments.
Fixes#17590.
Change-Id: Ia541dea1f2f015c1b21f5b3ae44aacdec60a8aba
Reviewed-on: https://go-review.googlesource.com/37386
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Starting the error message with "expecting" rather than "missing"
causes the syntax error mechanism to add additional helpful info
(it recognizes "expecting" but not "missing").
Fixes#17328.
Change-Id: I8482ca5e5a6a6b22e0ed0d831b7328e264156334
Reviewed-on: https://go-review.googlesource.com/36637
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Towards better syntax error messages: With this change, the parser knows whether
a semicolon was an actual ';' in the source, or whether it was an automatically
inserted semicolon as result of a '\n' or EOF. Using this information in error
messages makes them more understandable.
For #17328.
Change-Id: I8cd9accee8681b62569d0ecef922d38682b401eb
Reviewed-on: https://go-review.googlesource.com/36636
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This makes a bunch of changes to package syntax to tweak line numbers
for AST nodes. For example, short variable declaration statements are
now associated with the location of the ":=" token, and function calls
are associated with the location of the final ")" token. These help
satisfy many unit tests that assume the old parser's behavior.
Because many of these changes are questionable, they're guarded behind
a new "gcCompat" const to make them easy to identify and revisit in
the future.
A handful of remaining tests are too difficult to make behave
identically. These have been updated to execute with -newparser=0 and
comments explaining why they need to be fixed.
all.bash now passes with both the old and new parsers.
Change-Id: Iab834b71ca8698d39269f261eb5c92a0d55a3bf4
Reviewed-on: https://go-review.googlesource.com/27199
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Removes an intermediate layer of functions that was clogging up a
corner of the compiler's profile graph.
I can't measure a performance improvement running a large build
like jujud, but the profile reports less total time spent in
gc.(*lexer).getr.
Change-Id: I3000585cfcb0f9729d3a3859e9023690a6528591
Reviewed-on: https://go-review.googlesource.com/20565
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Use a combination of follow- and stop-token lists and nesting levels
to better synchronize parser after a syntax error.
Fixes#13319.
Change-Id: I9592e0b5b3ba782fb9f9315fea16163328e204f7
Reviewed-on: https://go-review.googlesource.com/17080
Reviewed-by: Chris Manghane <cmang@golang.org>
This is a translation of the yacc-based parser with adjustements
to make the grammar work for a recursive-descent parser followed
by cleanups and simplifications.
The yacc actions were mostly literally copied for correctness
with better temporary names.
A few of the syntax tests were adjusted for slightly different
error messages (it is very difficult to match the yacc-based
error messages in all cases, and sometimes the new parser could
produce better errors).
The new parser is enabled by default.
To switch back to the yacc-based parser, set -oldparser.
To hardwire the switch back, uncomment "oldparser = 1" in lex.go.
- passes all.bash
- ~18% reduced parse time per file on average for make.bash
- ~3% reduced compile time for building cmd/compile
Change-Id: Icb5651bb9d8b9f66261762d2c94a03793050d4ce
Reviewed-on: https://go-review.googlesource.com/16665
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
const1.go:33: error: integer constant overflow
<similar errors omitted>
const1.go:64: error: division by zero
const1.go:67: error: floating point constant overflow
const1.go:68: error: floating point constant overflow
const1.go:69: error: floating point constant overflow
const1.go:70: error: division by zero
const1.go:71: error: expected integer type
const1.go:77: error: argument 1 has incompatible type (cannot use type int8 as type int)
const1.go:78: error: argument 1 has incompatible type (cannot use type int8 as type int)
const1.go:79: error: argument 1 has incompatible type (cannot use type uint8 as type int)
const1.go:81: error: argument 1 has incompatible type (cannot use type float32 as type int)
const1.go:82: error: argument 1 has incompatible type (cannot use type float64 as type int)
const1.go:83: error: floating point constant truncated to integer
const1.go:85: error: argument 1 has incompatible type (cannot use type float64 as type int)
const1.go:86: error: argument 1 has incompatible type (cannot use type string as type int)
const1.go:87: error: argument 1 has incompatible type (cannot use type bool as type int)
const1.go:90: error: const initializer cannot be nil
const1.go:91: error: expression is not constant
const1.go:92: error: expression is not constant
const1.go:93: error: invalid constant type
const1.go:94: error: invalid constant type
fixedbugs/bug462.go:17: error: unknown field 'os.File' in 'T'
fixedbugs/issue3705.go:9: error: cannot declare init - must be func
fixedbugs/issue4251.go:12: error: inverted slice range
fixedbugs/issue4251.go:16: error: inverted slice range
fixedbugs/issue4251.go:20: error: inverted slice range
fixedbugs/issue4405.go:11: error: invalid character 0x7 in identifier
fixedbugs/issue4405.go:12: error: invalid character 0x8 in identifier
fixedbugs/issue4405.go:13: error: invalid character 0xb in identifier
fixedbugs/issue4405.go:14: error: invalid character 0xc in identifier
fixedbugs/issue4429.go:15: error: expected pointer
fixedbugs/issue4517d.go:9: error: cannot import package as init
fixedbugs/issue4545.go:17: error: invalid context-determined non-integer type for left operand of shift
fixedbugs/issue4545.go:16: error: incompatible types in binary expression
fixedbugs/issue4610.go:15: error: expected ';' or '}' or newline
fixedbugs/issue4610.go:16: error: expected declaration
fixedbugs/issue4654.go:15: error: value computed is not used
<similar errors omitted>
fixedbugs/issue4776.go:9: error: program must start with package clause
fixedbugs/issue4776.go:9: error: expected ';' or newline after package clause
fixedbugs/issue4813.go:31: error: index must be integer
<similar errors omitted>
fixedbugs/issue4847.go:22: error: initialization expression for 'matchAny' depends upon itself
fixedbugs/issue5089.go:13: error: redefinition of 'bufio.Buffered': receiver name changed
fixedbugs/issue5089.go:11: note: previous definition of 'bufio.Buffered' was here
fixedbugs/issue5172.go:17: error: reference to undefined field or method 'bar'
fixedbugs/issue5172.go:18: error: reference to undefined field or method 'bar'
fixedbugs/issue5172.go:12: error: use of undefined type 'bar'
fixedbugs/issue5358.go:16: error: argument 2 has incompatible type
fixedbugs/issue5581.go:29: error: use of undefined type 'Blah'
funcdup.go:10: error: redefinition of 'i'
funcdup.go:10: note: previous definition of 'i' was here
<similar errors omitted>
funcdup2.go:10: error: redefinition of 'i'
funcdup2.go:10: note: previous definition of 'i' was here
<similar errors omitted>
slice3err.go:20: error: middle index required in 3-index slice
<similar errors omitted>
slice3err.go:20: error: final index required in 3-index slice
<similar errors omitted>
slice3err.go:21: error: final index required in 3-index slice
slice3err.go:46: error: invalid 3-index slice of string
<similar errors omitted>
slice3err.go:57: error: inverted slice range
<similar errors omitted>
slice3err.go:62: error: invalid slice index: capacity less than length
slice3err.go:64: error: invalid slice index: capacity less than start
slice3err.go:65: error: invalid slice index: capacity less than start
slice3err.go:66: error: invalid slice index: capacity less than start
slice3err.go:68: error: invalid slice index: capacity less than length
slice3err.go:70: error: invalid slice index: capacity less than start
slice3err.go:80: error: invalid slice index: capacity less than length
slice3err.go:82: error: invalid slice index: capacity less than start
slice3err.go:83: error: invalid slice index: capacity less than start
slice3err.go:84: error: invalid slice index: capacity less than start
slice3err.go:86: error: invalid slice index: capacity less than length
slice3err.go:88: error: invalid slice index: capacity less than start
slice3err.go:99: error: array index out of bounds
<similar errors omitted>
slice3err.go:106: error: invalid slice index: capacity less than length
slice3err.go:107: error: invalid slice index: capacity less than start
slice3err.go:118: error: invalid slice index: capacity less than length
slice3err.go:119: error: invalid slice index: capacity less than start
syntax/semi1.go:10: error: missing '{' after if clause
syntax/semi1.go:10: error: reference to undefined name 'x'
syntax/semi1.go:10: error: reference to undefined name 'y'
syntax/semi1.go:12: error: reference to undefined name 'z'
syntax/semi2.go:10: error: missing '{' after switch clause
syntax/semi2.go:10: error: reference to undefined name 'x'
syntax/semi3.go:10: error: missing '{' after for clause
syntax/semi3.go:10: error: reference to undefined name 'x'
syntax/semi3.go:10: error: reference to undefined name 'y'
syntax/semi3.go:10: error: reference to undefined name 'z'
syntax/semi3.go:12: error: reference to undefined name 'z'
syntax/semi4.go:11: error: missing '{' after for clause
syntax/semi4.go:10: error: reference to undefined name 'x'
syntax/semi4.go:12: error: reference to undefined name 'z'
typecheck.go:12: error: reference to undefined name 'b'
typecheck.go:17: error: reference to undefined name 'c'
typecheck.go:11: error: use of undefined type 'b'
typecheck.go:16: error: not enough arguments
typecheck.go:17: error: not enough arguments
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/41520044
syntax/*: update messages
sliceerr3.go: bizarre new error fixed by deleting a space.
I could have sworn I ran all.bash before submitting the CL that triggered these.
TBR=golang-dev@googlegroups.com
R=golang-dev
CC=golang-dev
https://golang.org/cl/12812044
complit1.go:37:34: error: may only omit types within composite literals of slice, array, or map type
complit1.go:38:19: error: may only omit types within composite literals of slice, array, or map type
complit1.go:18:21: error: slice of unaddressable value
complit1.go:19:10: error: slice of unaddressable value
complit1.go:20:9: error: slice of unaddressable value
convert1.go:28:13: error: invalid type conversion
convert1.go:32:12: error: invalid type conversion (cannot use type string as type Tint64)
convert1.go:36:12: error: invalid type conversion
convert1.go:37:13: error: invalid type conversion
convert1.go:40:11: error: invalid type conversion
convert1.go:41:12: error: invalid type conversion
convert1.go:44:12: error: invalid type conversion
convert1.go:46:13: error: invalid type conversion
convert1.go:48:11: error: invalid type conversion
convert1.go:50:12: error: invalid type conversion
convert1.go:52:6: error: invalid type conversion
convert1.go:53:12: error: invalid type conversion
convert1.go:54:12: error: invalid type conversion
convert1.go:56:13: error: invalid type conversion
convert1.go:57:11: error: invalid type conversion
convert1.go:58:11: error: invalid type conversion
convert1.go:64:13: error: invalid type conversion
convert1.go:68:12: error: invalid type conversion (cannot use type Tstring as type Tint64)
convert1.go:72:12: error: invalid type conversion
convert1.go:73:13: error: invalid type conversion
convert1.go:76:11: error: invalid type conversion (cannot use type Tbyte as type Trune)
convert1.go:77:12: error: invalid type conversion (cannot use type Tbyte as type Tint64)
convert1.go:80:12: error: invalid type conversion
convert1.go:82:13: error: invalid type conversion
convert1.go:84:11: error: invalid type conversion (cannot use type Trune as type Tbyte)
convert1.go:86:12: error: invalid type conversion (cannot use type Trune as type Tint64)
convert1.go:88:6: error: invalid type conversion (cannot use type Tint64 as type string)
convert1.go:89:12: error: invalid type conversion
convert1.go:90:12: error: invalid type conversion
convert1.go:92:13: error: invalid type conversion (cannot use type Tint64 as type Tstring)
convert1.go:93:11: error: invalid type conversion (cannot use type Tint64 as type Tbyte)
convert1.go:94:11: error: invalid type conversion (cannot use type Tint64 as type Trune)
fixedbugs/bug195.go:9:21: error: interface contains embedded non-interface
fixedbugs/bug195.go:12:21: error: interface contains embedded non-interface
fixedbugs/bug195.go:15:15: error: interface contains embedded non-interface
fixedbugs/bug195.go:18:2: error: invalid recursive interface
fixedbugs/bug195.go:26:2: error: invalid recursive interface
fixedbugs/bug195.go:22:2: error: invalid recursive interface
fixedbugs/bug251.go:15:2: error: invalid recursive interface
fixedbugs/bug251.go:11:2: error: invalid recursive interface
fixedbugs/bug374.go:18:34: error: use of undefined type ‘xxxx’
fixedbugs/bug374.go:16:5: error: incompatible type in initialization (incompatible type for method ‘m’ (different number of parameters))
fixedbugs/bug383.go:11:2: error: expected boolean expression
fixedbugs/bug383.go:12:2: error: expected boolean expression
fixedbugs/bug386.go:10:25: error: incompatible type for return value 1 (type has no methods)
fixedbugs/bug386.go:12:25: error: incompatible type for return value 1 (type has no methods)
fixedbugs/bug388.go:12:10: error: invalid named/anonymous mix
fixedbugs/bug388.go:17:19: error: non-name on left side of ‘:=’
fixedbugs/bug388.go:22:9: error: non-name on left side of ‘:=’
fixedbugs/bug388.go:27:10: error: expected type
fixedbugs/bug388.go:32:9: error: expected type
fixedbugs/bug388.go:23:14: error: reference to field ‘i’ in object which has no fields or methods
fixedbugs/bug388.go:18:18: error: invalid use of type
fixedbugs/bug389.go:12:5: error: incompatible type in initialization (different parameter types)
fixedbugs/bug390.go:15:24: error: expected integer, floating, or complex type
fixedbugs/bug394.go:10:1: error: expected declaration
fixedbugs/bug397.go:12:2: error: incompatible type for element 2 key in map construction
switch3.go:18:2: error: incompatible types in binary expression
switch3.go:22:2: error: incompatible types in binary expression
switch3.go:28:2: error: map can only be compared to nil
switch3.go:35:2: error: slice can only be compared to nil
switch3.go:42:2: error: func can only be compared to nil
syntax/else.go:11:9: error: expected ‘if’ or ‘{’
typeswitch2.go:15:2: error: duplicate type in switch
typeswitch2.go:19:2: error: duplicate type in switch
typeswitch2.go:26:2: error: duplicate type in switch
typeswitch2.go:40:9: error: ‘t’ declared and not used
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5573073
chan.go:11:1: error: unexpected ‘}’ in channel type
chan.go:13:16: error: unexpected ‘)’ in channel type
chan.go:16:16: error: unexpected comma in channel type
R=golang-dev, rsc1
CC=golang-dev
https://golang.org/cl/4313055
vareq.go:10:25: error: expected ';' or '}' or newline
vareq1.go:9:24: error: expected ';' or newline after top level declaration
R=rsc
CC=golang-dev
https://golang.org/cl/2132045
With the recursive descent parser that gccgo uses, I think
that it doesn't make sense to try to match a statement where a
statement is not expected. If the construct is not a
statement, you will just get bizarre error messages.
topexpr.go:9:1: error: expected declaration
topexpr.go:14:1: error: expected declaration
topexpr.go:19:1: error: expected declaration
R=rsc, r2
CC=golang-dev
https://golang.org/cl/2175041
bug121.go:12:3: error: name list not allowed in interface type
bug121.go:16:2: error: expected signature or type name
semi1.go:10:76: error: unexpected semicolon or newline before ‘{’
semi1.go:10:5: error: reference to undefined name ‘x’
semi1.go:10:8: error: reference to undefined name ‘y’
semi1.go:12:3: error: reference to undefined name ‘z’
semi2.go:10:79: error: unexpected semicolon or newline before ‘{’
semi2.go:10:9: error: reference to undefined name ‘x’
semi3.go:10:79: error: unexpected semicolon or newline before ‘{’
semi3.go:10:6: error: reference to undefined name ‘x’
semi3.go:10:9: error: reference to undefined name ‘y’
semi3.go:10:12: error: reference to undefined name ‘z’
semi3.go:12:3: error: reference to undefined name ‘z’
semi4.go:11:2: error: unexpected semicolon or newline before ‘{’
semi4.go:10:6: error: reference to undefined name ‘x’
semi4.go:12:3: error: reference to undefined name ‘z’
semi5.go:10:1: error: unexpected semicolon or newline before ‘{’
semi7.go:11:2: error: unexpected semicolon or newline before ‘else’
semi7.go:10:5: error: reference to undefined name ‘x’
slice.go:9:11: error: missing lower bound in slice expression
slice.go:9:9: error: reference to undefined name ‘y’
slice.go:9:12: error: reference to undefined name ‘z’
R=rsc
CC=golang-dev
https://golang.org/cl/201061
* 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
