cmd/compile/internal/syntax: expose additional information for gc

gc needs access to line offsets for Nodes. It also needs access to the
end line offset for function bodies so it knows what line number to
use for things like implicit returns and defer executions.

Lastly, include an extra bool to distinguish between simple and full
slice expressions. This is redundant in valid parse trees, but needed
by gc for producing complete warnings in invalid inputs.

Change-Id: I64baf334a35c72336d26fa6755c67eb9d6f4e93c
Reviewed-on: https://go-review.googlesource.com/27196
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/syntax/nodes.go

@@ -8,6 +8,7 @@ package syntax
 // Nodes
 
 type Node interface {
+	Line() uint32
 	aNode()
 }
 
@@ -19,6 +20,10 @@ type node struct {
 
 func (*node) aNode() {}
 
+func (n *node) Line() uint32 {
+	return n.line
+}
+
 func (n *node) init(p *parser) {
 	n.pos = uint32(p.pos)
 	n.line = uint32(p.line)
@@ -80,11 +85,12 @@ type (
 	}
 
 	FuncDecl struct {
-		Attr map[string]bool // go:attr map
-		Recv *Field          // nil means regular function
-		Name *Name
-		Type *FuncType
-		Body []Stmt // nil means no body (forward declaration)
+		Attr    map[string]bool // go:attr map
+		Recv    *Field          // nil means regular function
+		Name    *Name
+		Type    *FuncType
+		Body    []Stmt // nil means no body (forward declaration)
+		EndLine uint32 // TODO(mdempsky): Cleaner solution.
 		decl
 	}
 )
@@ -136,8 +142,9 @@ type (
 
 	// func Type { Body }
 	FuncLit struct {
-		Type *FuncType
-		Body []Stmt
+		Type    *FuncType
+		Body    []Stmt
+		EndLine uint32 // TODO(mdempsky): Cleaner solution.
 		expr
 	}
 
@@ -165,6 +172,11 @@ type (
 	SliceExpr struct {
 		X     Expr
 		Index [3]Expr
+		// Full indicates whether this is a simple or full slice expression.
+		// In a valid AST, this is equivalent to Index[2] != nil.
+		// TODO(mdempsky): This is only needed to report the "3-index
+		// slice of string" error when Index[2] is missing.
+		Full bool
 		expr
 	}