internal/core/export: fix crash in dynamic fields

Silly alignment issue in comprehensions.

Fixes #1910

Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: Ie578d03978eac7ef4ccee164100ad5ef7a9b0095
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/543534
Unity-Result: CUEcueckoo <cueckoo@cuelang.org>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>

internal/core/export/adt.go

@@ -54,6 +54,9 @@ func (e *exporter) adt(env *adt.Environment, expr adt.Elem) ast.Expr {
 		// s := e.frame(0).scope
 
 		s := &ast.StructLit{}
+		// TODO: ensure e.node() is set in more cases. Right now it is not
+		// always set in mergeValues, even in cases where it could be. Better
+		// to be conservative for now, though.
 		env := &adt.Environment{Up: env, Vertex: e.node()}
 
 		for _, d := range x.Decls {
@@ -566,7 +569,7 @@ loop:
 	for {
 		switch x := y.(type) {
 		case *adt.ForClause:
-			env := &adt.Environment{Up: env, Vertex: empty}
+			env = &adt.Environment{Up: env, Vertex: empty}
 			value := e.ident(x.Value)
 			src := e.innerExpr(env, x.Src)
 			clause := &ast.ForClause{Value: value, Source: src}
@@ -592,7 +595,7 @@ loop:
 			y = x.Dst
 
 		case *adt.LetClause:
-			env := &adt.Environment{Up: env, Vertex: empty}
+			env = &adt.Environment{Up: env, Vertex: empty}
 			expr := e.innerExpr(env, x.Expr)
 			clause := &ast.LetClause{
 				Ident: e.ident(x.Label),
@@ -615,6 +618,12 @@ loop:
 		}
 	}
 
+	// If this is an "unwrapped" comprehension, we need to also
+	// account for the curly braces of the original comprehension.
+	if comp.Nest() > 0 {
+		env = &adt.Environment{Up: env, Vertex: empty}
+	}
+
 	v := e.expr(env, adt.ToExpr(comp.Value))
 	if _, ok := v.(*ast.StructLit); !ok {
 		v = ast.NewStruct(ast.Embed(v))

internal/core/export/testdata/main/adt.txtar

@@ -13,6 +13,16 @@ d2: C="foo\(bar)": {
 	foo:  C.name
 }
 
+// Issue #1910
+a: _
+comp: {
+	for k, v in [0]
+	let w = v {
+		"\(a)": w
+		"\(bar)": w
+	}
+}
+
 bytes: '\xeb \x1a\xf5\xaa\xf0\xd6\x06)'
 
 c1: mystrings.Contains("aa", "a")
@@ -141,6 +151,13 @@ d2: {
 		foo:  C.name
 	}
 }
+a: _
+comp: {
+	for k, v in [0] let w = v {
+		"\(a)": w
+		"bar":  w
+	}
+}
 bytes: '\xeb \x1a\xf5\xaa\xf0\xd6\x06)'
 c1:    mystrings.Contains("aa", "a")
 s1:    """
@@ -230,6 +247,11 @@ errorListDef: {
 [d2 foobar]
 [d2 foobar name]
 [d2 foobar foo]
+[a]
+- Issue #1910
+
+[comp]
+[comp bar]
 [bytes]
 [c1]
 [s1]
@@ -312,6 +334,15 @@ _|_ // e3: index out of range [2] with length 2
 			foo:  "xx"
 		}
 	}
+
+	// Issue #1910
+	a: _
+	comp: {
+		for k, v in [0] let w = v {
+			"\(a)": w
+			"bar":  w
+		}
+	}
 	bytes: '\xeb \x1a\xf5\xaa\xf0\xd6\x06)'
 	c1:    true
 	s1: """