Drop the kind discriminator from the CST: shapes discriminate structurally

kind carried zero information — a leaf always has tokenType and a node always
has rule + children, two disjoint field sets, so the tag was derivable from
property presence. A leaf is now {tokenType, offset, end} and a node
{rule, children, offset, end}; consumers discriminate with 'tokenType' in n /
'children' in n (TypeScript property-presence narrowing covers the union), and
the generated *.cst-types.ts drop the field. The cst-text-invariant gate now
pins the full shape on both sides: no kind, no text, leaf/node field sets
exact, sane spans.

In-engine reads (the no-unary-LHS head check, markup tag-name extraction, the
html/coverage tree walkers, exec-trace) switch to structural checks; the
emitted pratt path simplifies (head.tokenType === '$operator' alone — a node's
tokenType is undefined and never matches).

interp ≡ emit on the full 18,805-file corpus, reject messages identical,
27/27 gates. Serialized CSTs shrink by one field per object; bench:
+3.4..+6.7% aggregate, 4/4 runs positive (one fewer slot per object and one
fewer store per build).

Author: johnsoncodehk

html.cst-types.ts

@@ -30,13 +30,11 @@ export type TokenType =
 
 /** A terminal: one lexer token (or synthetic keyword/punct/operator leaf). */
 export interface CstLeaf extends CstPos {
-  kind: 'leaf';
   tokenType: TokenType;
 }
 
 /** `Element` node. Children (flattened, in source order) are drawn from: */
 export interface ElementNode extends CstPos {
-  kind: 'node';
   rule: 'Element';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -50,7 +48,6 @@ export interface ElementNode extends CstPos {
 
 /** `Attr` node. Children (flattened, in source order) are drawn from: */
 export interface AttrNode extends CstPos {
-  kind: 'node';
   rule: 'Attr';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -62,7 +59,6 @@ export interface AttrNode extends CstPos {
 
 /** `Node` node. Children (flattened, in source order) are drawn from: */
 export interface NodeNode extends CstPos {
-  kind: 'node';
   rule: 'Node';
   children: Array<
     | (CstLeaf & { tokenType: 'Comment' })
@@ -74,7 +70,6 @@ export interface NodeNode extends CstPos {
 
 /** `Document` node. Children (flattened, in source order) are drawn from: */
 export interface DocumentNode extends CstPos {
-  kind: 'node';
   rule: 'Document';
   children: Array<
     | (CstLeaf & { tokenType: 'Comment' })

javascript.cst-types.ts

@@ -39,20 +39,17 @@ export type TokenType =
 
 /** A terminal: one lexer token (or synthetic keyword/punct/operator leaf). */
 export interface CstLeaf extends CstPos {
-  kind: 'leaf';
   tokenType: TokenType;
 }
 
 /** Synthetic node the parser builds for an interpolated template literal. */
 export interface $templateNode extends CstPos {
-  kind: 'node';
   rule: '$template';
   children: CstChild[];
 }
 
 /** `DecoratorExpr` node. Children (flattened, in source order) are drawn from: */
 export interface DecoratorExprNode extends CstPos {
-  kind: 'node';
   rule: 'DecoratorExpr';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -63,7 +60,6 @@ export interface DecoratorExprNode extends CstPos {
 
 /** `Expr` node. Children (flattened, in source order) are drawn from: */
 export interface ExprNode extends CstPos {
-  kind: 'node';
   rule: 'Expr';
   children: Array<
     | $templateNode
@@ -94,7 +90,6 @@ export interface ExprNode extends CstPos {
 
 /** `Prop` node. Children (flattened, in source order) are drawn from: */
 export interface PropNode extends CstPos {
-  kind: 'node';
   rule: 'Prop';
   children: Array<
     | (CstLeaf & { tokenType: '$keyword' })
@@ -109,7 +104,6 @@ export interface PropNode extends CstPos {
 
 /** `MemberName` node. Children (flattened, in source order) are drawn from: */
 export interface MemberNameNode extends CstPos {
-  kind: 'node';
   rule: 'MemberName';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -127,7 +121,6 @@ export interface MemberNameNode extends CstPos {
 
 /** `NewTarget` node. Children (flattened, in source order) are drawn from: */
 export interface NewTargetNode extends CstPos {
-  kind: 'node';
   rule: 'NewTarget';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -139,7 +132,6 @@ export interface NewTargetNode extends CstPos {
 
 /** `ClassHeritage` node. Children (flattened, in source order) are drawn from: */
 export interface ClassHeritageNode extends CstPos {
-  kind: 'node';
   rule: 'ClassHeritage';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -151,7 +143,6 @@ export interface ClassHeritageNode extends CstPos {
 
 /** `Stmt` node. Children (flattened, in source order) are drawn from: */
 export interface StmtNode extends CstPos {
-  kind: 'node';
   rule: 'Stmt';
   children: Array<
     | (CstLeaf & { tokenType: '$keyword' })
@@ -171,7 +162,6 @@ export interface StmtNode extends CstPos {
 
 /** `Block` node. Children (flattened, in source order) are drawn from: */
 export interface BlockNode extends CstPos {
-  kind: 'node';
   rule: 'Block';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -181,7 +171,6 @@ export interface BlockNode extends CstPos {
 
 /** `BindingProperty` node. Children (flattened, in source order) are drawn from: */
 export interface BindingPropertyNode extends CstPos {
-  kind: 'node';
   rule: 'BindingProperty';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -196,7 +185,6 @@ export interface BindingPropertyNode extends CstPos {
 
 /** `BindingElement` node. Children (flattened, in source order) are drawn from: */
 export interface BindingElementNode extends CstPos {
-  kind: 'node';
   rule: 'BindingElement';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -208,7 +196,6 @@ export interface BindingElementNode extends CstPos {
 
 /** `ArrayBindingElement` node. Children (flattened, in source order) are drawn from: */
 export interface ArrayBindingElementNode extends CstPos {
-  kind: 'node';
   rule: 'ArrayBindingElement';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -220,7 +207,6 @@ export interface ArrayBindingElementNode extends CstPos {
 
 /** `BindingPattern` node. Children (flattened, in source order) are drawn from: */
 export interface BindingPatternNode extends CstPos {
-  kind: 'node';
   rule: 'BindingPattern';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -231,7 +217,6 @@ export interface BindingPatternNode extends CstPos {
 
 /** `Binding` node. Children (flattened, in source order) are drawn from: */
 export interface BindingNode extends CstPos {
-  kind: 'node';
   rule: 'Binding';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -243,7 +228,6 @@ export interface BindingNode extends CstPos {
 
 /** `ForBinding` node. Children (flattened, in source order) are drawn from: */
 export interface ForBindingNode extends CstPos {
-  kind: 'node';
   rule: 'ForBinding';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -255,7 +239,6 @@ export interface ForBindingNode extends CstPos {
 
 /** `Param` node. Children (flattened, in source order) are drawn from: */
 export interface ParamNode extends CstPos {
-  kind: 'node';
   rule: 'Param';
   children: Array<
     | (CstLeaf & { tokenType: '$punct' })
@@ -268,7 +251,6 @@ export interface ParamNode extends CstPos {
 
 /** `ForHead` node. Children (flattened, in source order) are drawn from: */
 export interface ForHeadNode extends CstPos {
-  kind: 'node';
   rule: 'ForHead';
   children: Array<
     | (CstLeaf & { tokenType: '$keyword' })
@@ -280,7 +262,6 @@ export interface ForHeadNode extends CstPos {
 
 /** `SwitchCase` node. Children (flattened, in source order) are drawn from: */
 export interface SwitchCaseNode extends CstPos {
-  kind: 'node';
   rule: 'SwitchCase';
   children: Array<
     | (CstLeaf & { tokenType: '$keyword' })
@@ -292,7 +273,6 @@ export interface SwitchCaseNode extends CstPos {
 
 /** `Decl` node. Children (flattened, in source order) are drawn from: */
 export interface DeclNode extends CstPos {
-  kind: 'node';
   rule: 'Decl';
   children: Array<
     | (CstLeaf & { tokenType: '$keyword' })
@@ -314,7 +294,6 @@ export interface DeclNode extends CstPos {
 
 /** `ClassMember` node. Children (flattened, in source order) are drawn from: */
 export interface ClassMemberNode extends CstPos {
-  kind: 'node';
   rule: 'ClassMember';
   children: Array<
     | (CstLeaf & { tokenType: '$keyword' })
@@ -329,7 +308,6 @@ export interface ClassMemberNode extends CstPos {
 
 /** `ImportClause` node. Children (flattened, in source order) are drawn from: */
 export interface ImportClauseNode extends CstPos {
-  kind: 'node';
   rule: 'ImportClause';
   children: Array<
     | (CstLeaf & { tokenType: '$keyword' })
@@ -341,7 +319,6 @@ export interface ImportClauseNode extends CstPos {
 
 /** `ImportSpecifier` node. Children (flattened, in source order) are drawn from: */
 export interface ImportSpecifierNode extends CstPos {
-  kind: 'node';
   rule: 'ImportSpecifier';
   children: Array<
     | (CstLeaf & { tokenType: '$keyword' })
@@ -351,7 +328,6 @@ export interface ImportSpecifierNode extends CstPos {
 
 /** `Program` node. Children (flattened, in source order) are drawn from: */
 export interface ProgramNode extends CstPos {
-  kind: 'node';
   rule: 'Program';
   children: Array<
     | DeclNode