cmd/compile: track line directives w/ column information

Extend cmd/internal/src.PosBase to track column information,
and adjust the meaning of the PosBase position to mean the
position at which the PosBase's relative (line, col) position
starts (rather than indicating the position of the //line
directive). Because this semantic change is made in the
compiler's noder, it doesn't affect the logic of src.PosBase,
only its test setup (where PosBases are constructed with
corrected incomming positions). In short, src.PosBase now
matches syntax.PosBase with respect to the semantics of
src.PosBase.pos.

For #22662.

Change-Id: I5b1451cb88fff3f149920c2eec08b6167955ce27
Reviewed-on: https://go-review.googlesource.com/96535
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/test/fixedbugs/issue22662.go b/test/fixedbugs/issue22662.go
new file mode 100644
index 0000000000..a1f00bfac3
--- /dev/null
+++ b/test/fixedbugs/issue22662.go
@@ -0,0 +1,46 @@
+// run
+
+// Copyright 2018 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.
+
+// Verify effect of various line directives.
+// TODO: check columns
+
+package main
+
+import (
+	"fmt"
+	"runtime"
+)
+
+func check(file string, line int) {
+	_, f, l, ok := runtime.Caller(1)
+	if !ok {
+		panic("runtime.Caller(1) failed")
+	}
+	if f != file || l != line {
+		panic(fmt.Sprintf("got %s:%d; want %s:%d", f, l, file, line))
+	}
+}
+
+func main() {
+//-style line directives
+//line :1
+	check("??", 1) // no file specified
+//line foo.go:1
+	check("foo.go", 1)
+//line bar.go:10:20
+	check("bar.go", 10)
+//line :11:22
+	check("bar.go", 11) // no file, but column specified => keep old filename
+
+/*-style line directives */
+/*line :1*/ check("??", 1) // no file specified
+/*line foo.go:1*/ check("foo.go", 1)
+/*line bar.go:10:20*/ check("bar.go", 10)
+/*line :11:22*/ check("bar.go", 11) // no file, but column specified => keep old filename
+
+	/*line :10*/ check("??", 10); /*line foo.go:20*/ check("foo.go", 20); /*line :30:1*/ check("foo.go", 30)
+	check("foo.go", 31)
+}