diff --git a/analyzer/test-common.go b/analyzer/test-common.go
index 8d65be3..53ff4b7 100644
--- a/analyzer/test-common.go
+++ b/analyzer/test-common.go
@@ -37,7 +37,7 @@ func testReaderErr (
 			test.Error("lexer returned error:", err)
 			return
 		}
-		err = ast.Parse(lx)
+		err = ast.Parse(fsplParser.UnitInfo { }, lx)
 		if err != nil {
 			test.Error("parser returned error:", err)
 			return
@@ -81,7 +81,7 @@ func testReader (test *testing.T, inputs ...io.Reader) {
 			test.Error("lexer returned error:", err)
 			return
 		}
-		err = ast.Parse(lx)
+		err = ast.Parse(fsplParser.UnitInfo { }, lx)
 		if err != nil {
 			test.Error("parser returned error:", err)
 			return
diff --git a/generator/test-common.go b/generator/test-common.go
index a4eb521..f66472a 100644
--- a/generator/test-common.go
+++ b/generator/test-common.go
@@ -15,7 +15,7 @@ func testString (test *testing.T, correct string, input string) {
 		test.Error("lexer returned error:", err)
 		return
 	}
-	err = ast.Parse(lx)
+	err = ast.Parse(fsplParser.UnitInfo { }, lx)
 	if err != nil && err != io.EOF{
 		test.Error("parser returned error:", err)
 		return
diff --git a/parser/fspl/parser.go b/parser/fspl/parser.go
index 0687804..12e5fb0 100644
--- a/parser/fspl/parser.go
+++ b/parser/fspl/parser.go
@@ -9,7 +9,9 @@ import "git.tebibyte.media/sashakoshka/fspl/parser"
 // a tree.
 type treeParser struct {
 	parser.Parser
-	tree  *Tree
+	tree *Tree
+	info UnitInfo
+	skim bool
 }
 
 // newParser creates a new parser that parses the output of the given lexer.
diff --git a/parser/fspl/test-common.go b/parser/fspl/test-common.go
index 6406827..5c746d4 100644
--- a/parser/fspl/test-common.go
+++ b/parser/fspl/test-common.go
@@ -14,7 +14,7 @@ func testString (test *testing.T, correct string, input string) {
 		test.Error("lexer returned error:\n" + errors.Format(err))
 		return
 	}
-	err = ast.Parse(lx)
+	err = ast.Parse(UnitInfo { }, lx)
 	if err != nil && err != io.EOF{
 		test.Error("parser returned error:\n" + errors.Format(err))
 		return
diff --git a/parser/fspl/tree.go b/parser/fspl/tree.go
index d1f8341..644a0c3 100644
--- a/parser/fspl/tree.go
+++ b/parser/fspl/tree.go
@@ -1,9 +1,17 @@
 package fsplParser
 
 import "fmt"
+import "github.com/google/uuid"
 import "git.tebibyte.media/sashakoshka/fspl/lexer"
 import "git.tebibyte.media/sashakoshka/fspl/entity"
 
+// UnitInfo maps nicknames to unit UUIDs, and gives a UUID for the unit being
+// parsed.
+type UnitInfo struct {
+	UUID uuid.UUID
+	Dependencies map[string] uuid.UUID
+}
+
 // Tree represents a parsed abstract syntax tree. It has no constructor and its
 // zero value can be used safely.
 type Tree struct {
@@ -21,10 +29,20 @@ func (this *Tree) String () string {
 	return out
 }
 
-
 // Parse parses the output of the given lexer into the tree.
-func (this *Tree) Parse (lx lexer.Lexer) error {
+func (this *Tree) Parse (info UnitInfo, lx lexer.Lexer) error {
 	parser, err := newParser(lx)
+	parser.info = info
+	if err != nil { return err }
+	return parser.parseInto(this)
+}
+
+// ParseDependency is like Parse, but does not keep code within functions and
+// methods, instead marking them as external.
+func (this *Tree) ParseDependency (info UnitInfo, lx lexer.Lexer) error {
+	parser, err := newParser(lx)
+	parser.skim = true
+	parser.info = info
 	if err != nil { return err }
 	return parser.parseInto(this)
 }