cmd/compile: initialize line number properly for temporaries

The expansion of structure, array, slice, and map literals
does not use the right line number in its introduced assignments
to temporaries, which leads to incorrect line number attribution
for expressions in those literals.

Inlining also incorrectly replaced the line numbers of args to
inlined functions.

This was revealed in CL 9721 because a now-avoided temporary
assignment introduced the correct line number.
I.e. before CL 9721
  "tmp_wrongline := expr"
was transformed to
  "tmp_rightline := expr; tmp_wrongline := tmp_rightline"

Also includes a repair to CL 10334 involving line numbers
where a spurious -1 remained (should have been 0, now is 0).

Fixes #11400.

Change-Id: I3a4687efe463977fa1e2c996606f4d91aaf22722
Reviewed-on: https://go-review.googlesource.com/11730
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Sameer Ajmani <sameer@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/compile/internal/gc/inl.go

@@ -787,8 +787,15 @@ func mkinlcall1(np **Node, fn *Node, isddd bool) {
 	call.Type = n.Type
 	call.Typecheck = 1
 
+	// Hide the args from setlno -- the parameters to the inlined
+	// call already have good line numbers that should be preserved.
+	args := as.Rlist
+	as.Rlist = nil
+
 	setlno(call, int(n.Lineno))
 
+	as.Rlist = args
+
 	//dumplist("call body", body);
 
 	*np = call

src/cmd/compile/internal/gc/sinit.go

@@ -380,6 +380,7 @@ func staticcopy(l *Node, r *Node, out **NodeList) bool {
 					rr.Orig = rr // completely separate copy
 					rr.Type = ll.Type
 					rr.Xoffset += e.Xoffset
+					setlineno(rr)
 					*out = list(*out, Nod(OAS, ll, rr))
 				}
 			}
@@ -484,6 +485,7 @@ func staticassign(l *Node, r *Node, out **NodeList) bool {
 			if e.Expr.Op == OLITERAL {
 				gdata(&n1, e.Expr, int(n1.Type.Width))
 			} else {
+				setlineno(e.Expr)
 				a = Nod(OXXX, nil, nil)
 				*a = n1
 				a.Orig = a // completely separate copy
@@ -636,6 +638,7 @@ func structlit(ctxt int, pass int, n *Node, var_ *Node, init **NodeList) {
 		}
 
 		// build list of var.field = expr
+		setlineno(value)
 		a = Nod(ODOT, var_, newname(index.Sym))
 
 		a = Nod(OAS, a, value)
@@ -703,6 +706,7 @@ func arraylit(ctxt int, pass int, n *Node, var_ *Node, init **NodeList) {
 		}
 
 		// build list of var[index] = value
+		setlineno(value)
 		a = Nod(OINDEX, var_, index)
 
 		a = Nod(OAS, a, value)
@@ -866,6 +870,7 @@ func slicelit(ctxt int, n *Node, var_ *Node, init **NodeList) {
 		}
 
 		// build list of var[c] = expr
+		setlineno(value)
 		a = Nod(OAS, a, value)
 
 		typecheck(&a, Etop)
@@ -954,6 +959,7 @@ func maplit(ctxt int, n *Node, var_ *Node, init **NodeList) {
 
 			if isliteral(index) && isliteral(value) {
 				// build vstat[b].a = key;
+				setlineno(index)
 				a = Nodintconst(b)
 
 				a = Nod(OINDEX, vstat, a)
@@ -965,6 +971,7 @@ func maplit(ctxt int, n *Node, var_ *Node, init **NodeList) {
 				*init = list(*init, a)
 
 				// build vstat[b].b = value;
+				setlineno(value)
 				a = Nodintconst(b)
 
 				a = Nod(OINDEX, vstat, a)
@@ -1032,15 +1039,18 @@ func maplit(ctxt int, n *Node, var_ *Node, init **NodeList) {
 			val = temp(var_.Type.Type)
 		}
 
+		setlineno(r.Left)
 		a = Nod(OAS, key, r.Left)
 		typecheck(&a, Etop)
 		walkstmt(&a)
 		*init = list(*init, a)
+		setlineno(r.Right)
 		a = Nod(OAS, val, r.Right)
 		typecheck(&a, Etop)
 		walkstmt(&a)
 		*init = list(*init, a)
 
+		setlineno(val)
 		a = Nod(OAS, Nod(OINDEX, var_, key), val)
 		typecheck(&a, Etop)
 		walkstmt(&a)

src/cmd/compile/internal/gc/subr.go

@@ -770,7 +770,7 @@ func treecopy(n *Node, lineno int32) *Node {
 		m.Left = treecopy(n.Left, lineno)
 		m.Right = treecopy(n.Right, lineno)
 		m.List = listtreecopy(n.List, lineno)
-		if lineno != -1 {
+		if lineno != 0 {
 			m.Lineno = lineno
 		}
 		if m.Name != nil && n.Op != ODCLFIELD {

src/runtime/symtab_test.go

@@ -45,3 +45,108 @@ func testCallerBar(t *testing.T) {
 		}
 	}
 }
+
+func lineNumber() int {
+	_, _, line, _ := runtime.Caller(1)
+	return line // return 0 for error
+}
+
+// Do not add/remove lines in this block without updating the line numbers.
+var firstLine = lineNumber() // 0
+var (                        // 1
+	lineVar1             = lineNumber()               // 2
+	lineVar2a, lineVar2b = lineNumber(), lineNumber() // 3
+)                        // 4
+var compLit = []struct { // 5
+	lineA, lineB int // 6
+}{ // 7
+	{ // 8
+		lineNumber(), lineNumber(), // 9
+	}, // 10
+	{ // 11
+		lineNumber(), // 12
+		lineNumber(), // 13
+	}, // 14
+	{ // 15
+		lineB: lineNumber(), // 16
+		lineA: lineNumber(), // 17
+	}, // 18
+}                                     // 19
+var arrayLit = [...]int{lineNumber(), // 20
+	lineNumber(), lineNumber(), // 21
+	lineNumber(), // 22
+}                                  // 23
+var sliceLit = []int{lineNumber(), // 24
+	lineNumber(), lineNumber(), // 25
+	lineNumber(), // 26
+}                         // 27
+var mapLit = map[int]int{ // 28
+	29:           lineNumber(), // 29
+	30:           lineNumber(), // 30
+	lineNumber(): 31,           // 31
+	lineNumber(): 32,           // 32
+}                           // 33
+var intLit = lineNumber() + // 34
+	lineNumber() + // 35
+			lineNumber() // 36
+func trythis() { // 37
+	recordLines(lineNumber(), // 38
+		lineNumber(), // 39
+		lineNumber()) // 40
+}
+
+// Modifications below this line are okay.
+
+var l38, l39, l40 int
+
+func recordLines(a, b, c int) {
+	l38 = a
+	l39 = b
+	l40 = c
+}
+
+func TestLineNumber(t *testing.T) {
+	trythis()
+	for _, test := range []struct {
+		name string
+		val  int
+		want int
+	}{
+		{"firstLine", firstLine, 0},
+		{"lineVar1", lineVar1, 2},
+		{"lineVar2a", lineVar2a, 3},
+		{"lineVar2b", lineVar2b, 3},
+		{"compLit[0].lineA", compLit[0].lineA, 9},
+		{"compLit[0].lineB", compLit[0].lineB, 9},
+		{"compLit[1].lineA", compLit[1].lineA, 12},
+		{"compLit[1].lineB", compLit[1].lineB, 13},
+		{"compLit[2].lineA", compLit[2].lineA, 17},
+		{"compLit[2].lineB", compLit[2].lineB, 16},
+
+		{"arrayLit[0]", arrayLit[0], 20},
+		{"arrayLit[1]", arrayLit[1], 21},
+		{"arrayLit[2]", arrayLit[2], 21},
+		{"arrayLit[3]", arrayLit[3], 22},
+
+		{"sliceLit[0]", sliceLit[0], 24},
+		{"sliceLit[1]", sliceLit[1], 25},
+		{"sliceLit[2]", sliceLit[2], 25},
+		{"sliceLit[3]", sliceLit[3], 26},
+
+		{"mapLit[29]", mapLit[29], 29},
+		{"mapLit[30]", mapLit[30], 30},
+		{"mapLit[31]", mapLit[31+firstLine] + firstLine, 31}, // nb it's the key not the value
+		{"mapLit[32]", mapLit[32+firstLine] + firstLine, 32}, // nb it's the key not the value
+
+		{"intLit", intLit - 2*firstLine, 34 + 35 + 36},
+
+		{"l38", l38, 38},
+		{"l39", l39, 39},
+		{"l40", l40, 40},
+	} {
+		if got := test.val - firstLine; got != test.want {
+			t.Errorf("%s on firstLine+%d want firstLine+%d (firstLine=%d, val=%d)",
+				test.name, got, test.want, firstLine, test.val)
+		}
+	}
+}