impr: block externals

packages/typegpu/src/resolutionCtx.ts

@@ -163,6 +163,7 @@ class ItemStateStackImpl implements ItemStateStack {
     this._stack.push({
       type: 'blockScope',
       declarations: new Map(),
+      externals: new Map(),
     });
   }
 
@@ -232,7 +233,8 @@ class ItemStateStackImpl implements ItemStateStack {
       }
 
       if (layer?.type === 'blockScope') {
-        const snippet = layer.declarations.get(id);
+        // the order matters
+        const snippet = layer.declarations.get(id) ?? layer.externals.get(id);
         if (snippet !== undefined) {
           return snippet;
         }
@@ -260,6 +262,30 @@ class ItemStateStackImpl implements ItemStateStack {
 
     throw new Error('No block scope found to define a variable in.');
   }
+
+  setBlockExternals(externals: Record<string, Snippet>) {
+    for (let i = this._stack.length - 1; i >= 0; --i) {
+      const layer = this._stack[i];
+      if (layer?.type === 'blockScope') {
+        Object.entries(externals).forEach(([id, snippet]) => {
+          layer.externals.set(id, snippet);
+        });
+        return;
+      }
+    }
+    throw new Error('No block scope found to set externals in.');
+  }
+
+  clearBlockExternals() {
+    for (let i = this._stack.length - 1; i >= 0; --i) {
+      const layer = this._stack[i];
+      if (layer?.type === 'blockScope') {
+        layer.externals.clear();
+        return;
+      }
+    }
+    throw new Error('No block scope found to clear externals in.');
+  }
 }
 
 const INDENT = [
@@ -429,6 +455,14 @@ export class ResolutionCtxImpl implements ResolutionCtx {
     this._itemStateStack.pop('blockScope');
   }
 
+  setBlockExternals(externals: Record<string, Snippet>) {
+    this._itemStateStack.setBlockExternals(externals);
+  }
+
+  clearBlockExternals() {
+    this._itemStateStack.clearBlockExternals();
+  }
+
   generateLog(op: string, args: Snippet[]): Snippet {
     return this.#logGenerator.generateLog(this, op, args);
   }

packages/typegpu/src/tgsl/generationHelpers.ts

@@ -92,6 +92,8 @@ export type GenerationCtx = ResolutionCtx & {
   generateLog(op: string, args: Snippet[]): Snippet;
   getById(id: string): Snippet | null;
   defineVariable(id: string, snippet: Snippet): void;
+  setBlockExternals(externals: Record<string, Snippet>): void;
+  clearBlockExternals(): void;
 
   /**
    * Types that are used in `return` statements are

packages/typegpu/src/tgsl/shaderGenerator.ts

@@ -2,10 +2,11 @@ import type { Block, Expression, Statement } from 'tinyest';
 import type { Snippet } from '../data/snippet.ts';
 import type { GenerationCtx } from './generationHelpers.ts';
 import type { BaseData } from '../data/wgslTypes.ts';
+import type { ExternalMap } from '../core/resolve/externals.ts';
 
 export interface ShaderGenerator {
   initGenerator(ctx: GenerationCtx): void;
-  block(body: Block): string;
+  block(body: Block, externalMap?: ExternalMap): string;
   identifier(id: string): Snippet;
   typedExpression(expression: Expression, expectedType: BaseData): Snippet;
   expression(expression: Expression): Snippet;

packages/typegpu/src/tgsl/wgslGenerator.ts

@@ -36,6 +36,7 @@ import {
 } from './conversion.ts';
 import {
   ArrayExpression,
+  coerceToSnippet,
   concretize,
   type GenerationCtx,
   numericLiteralToSnippet,
@@ -51,6 +52,7 @@ import type { AnyFn } from '../core/function/fnTypes.ts';
 import { arrayLength } from '../std/array.ts';
 import { AutoStruct } from '../data/autoStruct.ts';
 import { mathToStd } from './math.ts';
+import type { ExternalMap } from '../core/resolve/externals.ts';
 
 const { NodeTypeCatalog: NODE } = tinyest;
 
@@ -200,8 +202,19 @@ class WgslGenerator implements ShaderGenerator {
 
   public block(
     [_, statements]: tinyest.Block,
+    externalMap?: ExternalMap,
   ): string {
     this.ctx.pushBlockScope();
+
+    if (externalMap) {
+      const externals = Object.fromEntries(
+        Object.entries(externalMap).map((
+          [id, value],
+        ) => [id, coerceToSnippet(value)]),
+      );
+      this.ctx.setBlockExternals(externals);
+    }
+
     try {
       this.ctx.indent();
       const body = statements.map((statement) => this.statement(statement))
@@ -1233,8 +1246,6 @@ ${this.ctx.pre}else ${alternate}`;
         // If it's ephemeral, it's a value that cannot change. If it's a reference, we take
         // an implicit pointer to it
         let loopVarKind = 'let';
-        const loopVarName = this.ctx.makeNameValid(loopVar[1]);
-
         if (!isEphemeralSnippet(elementSnippet)) {
           if (elementSnippet.origin === 'constant-tgpu-const-ref') {
             loopVarKind = 'const';
@@ -1260,21 +1271,13 @@ ${this.ctx.pre}else ${alternate}`;
           }
         }
 
-        const loopVarSnippet = snip(
-          loopVarName,
-          elementType,
-          elementSnippet.origin,
-        );
-
-        this.ctx.defineVariable(loopVar[1], loopVarSnippet);
-
         const forStr =
           stitch`${this.ctx.pre}for (var ${index} = 0u; ${index} < ${
             tryConvertSnippet(this.ctx, elementCountSnippet, u32, false)
           }; ${index}++) {`;
-
         this.ctx.indent();
 
+        const loopVarName = this.ctx.makeNameValid(loopVar[1]);
         const loopVarDeclStr =
           stitch`${this.ctx.pre}${loopVarKind} ${loopVarName} = ${
             tryConvertSnippet(
@@ -1286,7 +1289,9 @@ ${this.ctx.pre}else ${alternate}`;
           };`;
 
         const bodyStr = `${this.ctx.pre}${
-          this.block(blockifySingleStatement(body))
+          this.block(blockifySingleStatement(body), {
+            [loopVar[1]]: snip(loopVarName, elementType, elementSnippet.origin),
+          })
         }`;
 
         this.ctx.dedent();

packages/typegpu/src/types.ts

@@ -124,6 +124,7 @@ export type SlotBindingLayer = {
 export type BlockScopeLayer = {
   type: 'blockScope';
   declarations: Map<string, Snippet>;
+  externals: Map<string, Snippet>;
 };
 
 export type StackLayer =
@@ -151,6 +152,8 @@ export interface ItemStateStack {
     externalMap: Record<string, unknown>,
   ): FunctionScopeLayer;
   pushBlockScope(): void;
+  setBlockExternals(externals: Record<string, Snippet>): void;
+  clearBlockExternals(): void;
 
   pop<T extends StackLayer['type']>(type: T): Extract<StackLayer, { type: T }>;
   pop(): StackLayer | undefined;

packages/typegpu/tests/tgsl/wgslGenerator.test.ts

@@ -1740,4 +1740,109 @@ describe('wgslGenerator', () => {
       }"
     `);
   });
+
+  it('block externals do not override identifiers', () => {
+    const f = () => {
+      'use gpu';
+      const y = 100;
+      const x = y;
+      return x;
+    };
+
+    const parsed = getMetaData(f)?.ast?.body as tinyest.Block;
+
+    provideCtx(ctx, () => {
+      ctx[$internal].itemStateStack.pushFunctionScope(
+        'normal',
+        [],
+        {},
+        d.u32,
+        {},
+      );
+
+      const res = wgslGenerator.block(
+        parsed,
+        { x: 42 },
+      );
+
+      expect(res).toMatchInlineSnapshot(`
+          "{
+            const y = 100;
+            const x = y;
+            return u32(x);
+          }"
+        `);
+    });
+  });
+
+  it('block externals are injected correctly', () => {
+    const f = () => {
+      'use gpu';
+      for (const x of []) {
+        const y = x;
+      }
+    };
+
+    const parsed = getMetaData(f)?.ast?.body as tinyest.Block;
+
+    provideCtx(ctx, () => {
+      ctx[$internal].itemStateStack.pushFunctionScope(
+        'normal',
+        [],
+        {},
+        d.Void,
+        {},
+      );
+
+      const res = wgslGenerator.block(
+        (parsed[1][0] as tinyest.ForOf)[3] as tinyest.Block,
+        { x: 67 },
+      );
+
+      expect(res).toMatchInlineSnapshot(`
+          "{
+            const y = 67;
+          }"
+        `);
+    });
+  });
+
+  it('block externals are respected in nested blocks', () => {
+    const f = () => {
+      'use gpu';
+      let result = d.i32(0);
+      const list = d.arrayOf(d.i32, 3)([1, 2, 3]);
+      for (const elem of list) {
+        {
+          // We use the `elem` in a nested block
+          result += elem;
+        }
+      }
+    };
+
+    const parsed = getMetaData(f)?.ast?.body as tinyest.Block;
+
+    provideCtx(ctx, () => {
+      ctx[$internal].itemStateStack.pushFunctionScope(
+        'normal',
+        [],
+        {},
+        d.Void,
+        {},
+      );
+
+      const res = wgslGenerator.block(
+        (parsed[1][2] as tinyest.ForOf)[3] as tinyest.Block,
+        { result: snip('result', d.i32, 'function'), elem: 7 },
+      );
+
+      expect(res).toMatchInlineSnapshot(`
+        "{
+          {
+            result += 7i;
+          }
+        }"
+      `);
+    });
+  });
 });