cmd/compile/internal/syntax: start line offset (column) numbers at 1

We could leave it alone and fix line offset (column) numbers when
reporting errors, but that is likely to cause confusion (internal
numbers don't match reported numbers). Instead, switch to default
numbering starting at 1.

For package syntax-internal use only, introduced constants defining
the line and column bases, and use them throughout the code and its
tests. It is possible to change these constants and package syntax
will continue to work. But changing them is going to break any client
that makes explicit assumptions about line and column numbers (which
is "all of them").

Change-Id: Ia3d136a8ec8d9372ed9c05ca47d3dff222cf030e
Reviewed-on: https://go-review.googlesource.com/37996
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 65 insertions, 65 deletions

diff --git a/src/cmd/compile/internal/syntax/scanner_test.go b/src/cmd/compile/internal/syntax/scanner_test.go
index 4d04e62875..e434db9a91 100644
--- a/src/cmd/compile/internal/syntax/scanner_test.go
+++ b/src/cmd/compile/internal/syntax/scanner_test.go
@@ -56,8 +56,8 @@ func TestTokens(t *testing.T) {
 	for i, want := range sampleTokens {
 		nlsemi := false
 
-		if got.line != uint(i+1) {
-			t.Errorf("got line %d; want %d", got.line, i+1)
+		if got.line != uint(i+linebase) {
+			t.Errorf("got line %d; want %d", got.line, i+linebase)
 		}
 
 		if got.tok != want.tok {
@@ -264,75 +264,75 @@ var sampleTokens = [...]struct {
 func TestScanErrors(t *testing.T) {
 	for _, test := range []struct {
 		src, msg  string
-		line, col uint
+		line, col uint // 0-based
 	}{
 		// Note: Positions for lexical errors are the earliest position
 		// where the error is apparent, not the beginning of the respective
 		// token.
 
 		// rune-level errors
-		{"fo\x00o", "invalid NUL character", 1, 2},
-		{"foo\n\ufeff bar", "invalid BOM in the middle of the file", 2, 0},
-		{"foo\n\n\xff    ", "invalid UTF-8 encoding", 3, 0},
+		{"fo\x00o", "invalid NUL character", 0, 2},
+		{"foo\n\ufeff bar", "invalid BOM in the middle of the file", 1, 0},
+		{"foo\n\n\xff    ", "invalid UTF-8 encoding", 2, 0},
 
 		// token-level errors
-		{"\u00BD" /* ½ */, "invalid identifier character U+00BD '½'", 1, 0},
-		{"\U0001d736\U0001d737\U0001d738_½" /* 𝜶𝜷𝜸_½ */, "invalid identifier character U+00BD '½'", 1, 13 /* byte offset */},
-		{"\U0001d7d8" /* 𝟘 */, "identifier cannot begin with digit U+1D7D8 '𝟘'", 1, 0},
-		{"foo\U0001d7d8_½" /* foo𝟘_½ */, "invalid identifier character U+00BD '½'", 1, 8 /* byte offset */},
-
-		{"x + ~y", "bitwise complement operator is ^", 1, 4},
-		{"foo$bar = 0", "invalid character U+0024 '$'", 1, 3},
-		{"const x = 0xyz", "malformed hex constant", 1, 12},
-		{"0123456789", "malformed octal constant", 1, 10},
-		{"0123456789. /* foobar", "comment not terminated", 1, 12},   // valid float constant
-		{"0123456789e0 /*\nfoobar", "comment not terminated", 1, 13}, // valid float constant
-		{"var a, b = 08, 07\n", "malformed octal constant", 1, 13},
-		{"(x + 1.0e+x)", "malformed floating-point constant exponent", 1, 10},
-
-		{`''`, "empty character literal or unescaped ' in character literal", 1, 1},
-		{"'\n", "newline in character literal", 1, 1},
-		{`'\`, "invalid character literal (missing closing ')", 1, 0},
-		{`'\'`, "invalid character literal (missing closing ')", 1, 0},
-		{`'\x`, "invalid character literal (missing closing ')", 1, 0},
-		{`'\x'`, "non-hex character in escape sequence: '", 1, 3},
-		{`'\y'`, "unknown escape sequence", 1, 2},
-		{`'\x0'`, "non-hex character in escape sequence: '", 1, 4},
-		{`'\00'`, "non-octal character in escape sequence: '", 1, 4},
-		{`'\377' /*`, "comment not terminated", 1, 7}, // valid octal escape
-		{`'\378`, "non-octal character in escape sequence: 8", 1, 4},
-		{`'\400'`, "octal escape value > 255: 256", 1, 5},
-		{`'xx`, "invalid character literal (missing closing ')", 1, 0},
-		{`'xx'`, "invalid character literal (more than one character)", 1, 0},
-
-		{"\"\n", "newline in string", 1, 1},
-		{`"`, "string not terminated", 1, 0},
-		{`"foo`, "string not terminated", 1, 0},
-		{"`", "string not terminated", 1, 0},
-		{"`foo", "string not terminated", 1, 0},
-		{"/*/", "comment not terminated", 1, 0},
-		{"/*\n\nfoo", "comment not terminated", 1, 0},
-		{"/*\n\nfoo", "comment not terminated", 1, 0},
-		{`"\`, "string not terminated", 1, 0},
-		{`"\"`, "string not terminated", 1, 0},
-		{`"\x`, "string not terminated", 1, 0},
-		{`"\x"`, "non-hex character in escape sequence: \"", 1, 3},
-		{`"\y"`, "unknown escape sequence", 1, 2},
-		{`"\x0"`, "non-hex character in escape sequence: \"", 1, 4},
-		{`"\00"`, "non-octal character in escape sequence: \"", 1, 4},
-		{`"\377" /*`, "comment not terminated", 1, 7}, // valid octal escape
-		{`"\378"`, "non-octal character in escape sequence: 8", 1, 4},
-		{`"\400"`, "octal escape value > 255: 256", 1, 5},
-
-		{`s := "foo\z"`, "unknown escape sequence", 1, 10},
-		{`s := "foo\z00\nbar"`, "unknown escape sequence", 1, 10},
-		{`"\x`, "string not terminated", 1, 0},
-		{`"\x"`, "non-hex character in escape sequence: \"", 1, 3},
-		{`var s string = "\x"`, "non-hex character in escape sequence: \"", 1, 18},
-		{`return "\Uffffffff"`, "escape sequence is invalid Unicode code point", 1, 18},
+		{"\u00BD" /* ½ */, "invalid identifier character U+00BD '½'", 0, 0},
+		{"\U0001d736\U0001d737\U0001d738_½" /* 𝜶𝜷𝜸_½ */, "invalid identifier character U+00BD '½'", 0, 13 /* byte offset */},
+		{"\U0001d7d8" /* 𝟘 */, "identifier cannot begin with digit U+1D7D8 '𝟘'", 0, 0},
+		{"foo\U0001d7d8_½" /* foo𝟘_½ */, "invalid identifier character U+00BD '½'", 0, 8 /* byte offset */},
+
+		{"x + ~y", "bitwise complement operator is ^", 0, 4},
+		{"foo$bar = 0", "invalid character U+0024 '$'", 0, 3},
+		{"const x = 0xyz", "malformed hex constant", 0, 12},
+		{"0123456789", "malformed octal constant", 0, 10},
+		{"0123456789. /* foobar", "comment not terminated", 0, 12},   // valid float constant
+		{"0123456789e0 /*\nfoobar", "comment not terminated", 0, 13}, // valid float constant
+		{"var a, b = 08, 07\n", "malformed octal constant", 0, 13},
+		{"(x + 1.0e+x)", "malformed floating-point constant exponent", 0, 10},
+
+		{`''`, "empty character literal or unescaped ' in character literal", 0, 1},
+		{"'\n", "newline in character literal", 0, 1},
+		{`'\`, "invalid character literal (missing closing ')", 0, 0},
+		{`'\'`, "invalid character literal (missing closing ')", 0, 0},
+		{`'\x`, "invalid character literal (missing closing ')", 0, 0},
+		{`'\x'`, "non-hex character in escape sequence: '", 0, 3},
+		{`'\y'`, "unknown escape sequence", 0, 2},
+		{`'\x0'`, "non-hex character in escape sequence: '", 0, 4},
+		{`'\00'`, "non-octal character in escape sequence: '", 0, 4},
+		{`'\377' /*`, "comment not terminated", 0, 7}, // valid octal escape
+		{`'\378`, "non-octal character in escape sequence: 8", 0, 4},
+		{`'\400'`, "octal escape value > 255: 256", 0, 5},
+		{`'xx`, "invalid character literal (missing closing ')", 0, 0},
+		{`'xx'`, "invalid character literal (more than one character)", 0, 0},
+
+		{"\"\n", "newline in string", 0, 1},
+		{`"`, "string not terminated", 0, 0},
+		{`"foo`, "string not terminated", 0, 0},
+		{"`", "string not terminated", 0, 0},
+		{"`foo", "string not terminated", 0, 0},
+		{"/*/", "comment not terminated", 0, 0},
+		{"/*\n\nfoo", "comment not terminated", 0, 0},
+		{"/*\n\nfoo", "comment not terminated", 0, 0},
+		{`"\`, "string not terminated", 0, 0},
+		{`"\"`, "string not terminated", 0, 0},
+		{`"\x`, "string not terminated", 0, 0},
+		{`"\x"`, "non-hex character in escape sequence: \"", 0, 3},
+		{`"\y"`, "unknown escape sequence", 0, 2},
+		{`"\x0"`, "non-hex character in escape sequence: \"", 0, 4},
+		{`"\00"`, "non-octal character in escape sequence: \"", 0, 4},
+		{`"\377" /*`, "comment not terminated", 0, 7}, // valid octal escape
+		{`"\378"`, "non-octal character in escape sequence: 8", 0, 4},
+		{`"\400"`, "octal escape value > 255: 256", 0, 5},
+
+		{`s := "foo\z"`, "unknown escape sequence", 0, 10},
+		{`s := "foo\z00\nbar"`, "unknown escape sequence", 0, 10},
+		{`"\x`, "string not terminated", 0, 0},
+		{`"\x"`, "non-hex character in escape sequence: \"", 0, 3},
+		{`var s string = "\x"`, "non-hex character in escape sequence: \"", 0, 18},
+		{`return "\Uffffffff"`, "escape sequence is invalid Unicode code point", 0, 18},
 
 		// former problem cases
-		{"package p\n\n\xef", "invalid UTF-8 encoding", 3, 0},
+		{"package p\n\n\xef", "invalid UTF-8 encoding", 2, 0},
 	} {
 		var s scanner
 		nerrors := 0
@@ -343,11 +343,11 @@ func TestScanErrors(t *testing.T) {
 				if msg != test.msg {
 					t.Errorf("%q: got msg = %q; want %q", test.src, msg, test.msg)
 				}
-				if line != test.line {
-					t.Errorf("%q: got line = %d; want %d", test.src, line, test.line)
+				if line != test.line+linebase {
+					t.Errorf("%q: got line = %d; want %d", test.src, line, test.line+linebase)
 				}
-				if col != test.col {
-					t.Errorf("%q: got col = %d; want %d", test.src, col, test.col)
+				if col != test.col+colbase {
+					t.Errorf("%q: got col = %d; want %d", test.src, col, test.col+colbase)
 				}
 			} else if nerrors > 1 {
 				// TODO(gri) make this use position info