diff --git a/src/ast.ts b/src/ast.ts
index 8f2d0f8..ea45c26 100644
--- a/src/ast.ts
+++ b/src/ast.ts
@@ -1,6 +1,7 @@
 import { ErrorEmitted, LoadedFile, Span, unreachable } from "./error";
 import { LitIntType } from "./lexer";
 import { ComplexMap } from "./utils";
+import { Instr, ValType } from "./wasm/defs";
 
 export type Phase = {
   res: unknown;
@@ -308,6 +309,12 @@ export type ExprTupleLiteral<P extends Phase> = {
   fields: Expr<P>[];
 };
 
+export type ExprInlineAsm = {
+  kind: "asm";
+  locals: ValType[];
+  instructions: Instr[];
+};
+
 export type ExprError = {
   kind: "error";
   err: ErrorEmitted;
@@ -330,6 +337,7 @@ export type ExprKind<P extends Phase> =
   | ExprBreak
   | ExprStructLiteral<P>
   | ExprTupleLiteral<P>
+  | ExprInlineAsm
   | ExprError;
 
 export type Expr<P extends Phase> = ExprKind<P> & {
@@ -485,6 +493,8 @@ export const BUILTINS = [
   "__memory_grow",
   "__i32_extend_to_i64_u",
   "___transmute",
+  "___asm",
+  "__locals",
 ] as const;
 
 export type BuiltinName = (typeof BUILTINS)[number];
@@ -920,6 +930,9 @@ export function superFoldExpr<From extends Phase, To extends Phase>(
         fields: expr.fields.map(folder.expr.bind(folder)),
       };
     }
+    case "asm": {
+      return { ...expr };
+    }
     case "error": {
       return { ...expr };
     }
diff --git a/src/codegen.ts b/src/codegen.ts
index 499a48c..d16bcf6 100644
--- a/src/codegen.ts
+++ b/src/codegen.ts
@@ -118,9 +118,7 @@ function appendData(cx: Context, newData: Uint8Array): number {
 
 const KNOWN_DEF_PATHS = [ALLOCATE_ITEM, DEALLOCATE_ITEM];
 
-function getKnownDefPaths(
-  pkgs: Pkg<Typecked>[],
-): ComplexMap<string[], ItemId> {
+function getKnownDefPaths(pkgs: Pkg<Typecked>[]): ComplexMap<string[], ItemId> {
   const knows = new ComplexMap<string[], ItemId>();
 
   const folder: Folder<Typecked, Typecked> = {
@@ -145,9 +143,7 @@ function getKnownDefPaths(
     },
   };
 
-  pkgs.forEach((pkg) =>
-    pkg.rootItems.forEach((item) => folder.item(item)),
-  );
+  pkgs.forEach((pkg) => pkg.rootItems.forEach((item) => folder.item(item)));
 
   return knows;
 }
@@ -380,16 +376,22 @@ function lowerFunc(cx: Context, func: ItemFunction<Typecked>) {
     scratchLocals: new Map(),
   };
 
-  lowerExpr(fcx, wasmFunc.body, fcx.func.body);
+  const body = fcx.func.body;
+  if (body.kind === "asm") {
+    fcx.wasm.locals = body.locals;
+    fcx.wasm.body = body.instructions;
+  } else {
+    lowerExpr(fcx, wasmFunc.body, body);
 
-  paramLocations.forEach((local) => {
-    const refcount = needsRefcount(local.ty);
-    if (refcount !== undefined) {
-      // TODO: correctly deal with tuples
-      loadVariable(wasmFunc.body, local);
-      subRefcount(fcx, wasmFunc.body, refcount);
-    }
-  });
+    paramLocations.forEach((local) => {
+      const refcount = needsRefcount(local.ty);
+      if (refcount !== undefined) {
+        // TODO: correctly deal with tuples
+        loadVariable(wasmFunc.body, local);
+        subRefcount(fcx, wasmFunc.body, refcount);
+      }
+    });
+  }
 
   const idx = fcx.cx.mod.funcs.length;
   fcx.cx.mod.funcs.push(wasmFunc);
@@ -1084,6 +1086,9 @@ function lowerExpr(
       expr.fields.forEach((field) => lowerExpr(fcx, instrs, field));
       break;
     }
+    case "asm": {
+      unreachable("asm");
+    }
     case "error":
       unreachable("codegen should never see errors");
     default: {
diff --git a/src/printer.ts b/src/printer.ts
index 9209a60..408dafc 100644
--- a/src/printer.ts
+++ b/src/printer.ts
@@ -211,6 +211,12 @@ function printExpr(expr: Expr<AnyPhase>, indent: number): string {
         .map((expr) => printExpr(expr, indent))
         .join(", ")})`;
     }
+    case "asm": {
+      return `___asm(___locals(${expr.locals
+        .map((valty) => `"${valty}"`)
+        // object object
+        .join(", ")}), ${expr.instructions.join(", ")})`;
+    }
     case "error":
       return "<ERROR>";
   }
diff --git a/src/typeck/expr.ts b/src/typeck/expr.ts
index 34ab9c3..a9eb8cc 100644
--- a/src/typeck/expr.ts
+++ b/src/typeck/expr.ts
@@ -28,12 +28,10 @@ import {
 } from "../ast";
 import { CompilerError, ErrorEmitted, Span, unreachable } from "../error";
 import { printTy } from "../printer";
+import { INSTRS, Instr, VALTYPES, ValType } from "../wasm/defs";
 import { TypeckCtx, emitError, mkTyFn, tyError, tyErrorFrom } from "./base";
 import { InferContext } from "./infer";
-import {
-  lowerAstTy,
-  typeOfItem,
-} from "./item";
+import { lowerAstTy, typeOfItem } from "./item";
 
 export function exprError(err: ErrorEmitted, span: Span): Expr<Typecked> {
   return {
@@ -129,6 +127,15 @@ export function checkBody(
     checkExpr: () => unreachable(),
   };
 
+  if (
+    body.kind === "call" &&
+    body.lhs.kind === "ident" &&
+    body.lhs.value.res.kind === "builtin" &&
+    body.lhs.value.res.name === "___asm"
+  ) {
+    return checkInlineAsm(cx, body, fnTy.returnTy);
+  }
+
   const checker: Folder<Resolved, Typecked> = {
     ...mkDefaultFolder(),
     expr(expr): Expr<Typecked> {
@@ -503,6 +510,9 @@ export function checkBody(
 
           return { ...expr, fields, ty };
         }
+        case "asm": {
+          unreachable("asm expression doesn't exist before type checking");
+        }
         case "error": {
           return { ...expr, ty: tyErrorFrom(expr) };
         }
@@ -530,6 +540,90 @@ export function checkBody(
   return resolved;
 }
 
+function checkInlineAsm(
+  cx: TypeckCtx,
+  body: Expr<Resolved> & ExprCall<Resolved>,
+  retTy: Ty,
+): Expr<Typecked> {
+  const err = (msg: string, span: Span): Expr<Typecked> =>
+    exprError(emitError(cx, new CompilerError(msg, span)), span);
+
+  const args = body.args;
+
+  if (
+    args.length < 1 ||
+    args[0].kind !== "call" ||
+    args[0].lhs.kind !== "ident" ||
+    args[0].lhs.value.res.kind !== "builtin" ||
+    args[0].lhs.value.res.name !== "__locals"
+  ) {
+    return err(
+      "inline assembly must have __locals() as first argument",
+      body.span,
+    );
+  }
+
+  const locals: ValType[] = [];
+  for (const local of args[0].args) {
+    const isValtype = (s: string): s is ValType =>
+      VALTYPES.includes(s as ValType);
+    if (
+      local.kind !== "literal" ||
+      local.value.kind !== "str" ||
+      !isValtype(local.value.value)
+    ) {
+      return err(
+        "inline assembly local must be string literal of value type",
+        local.span,
+      );
+    }
+    locals.push(local.value.value);
+  }
+
+  const instructions: Instr[] = [];
+  for (const expr of args.slice(1)) {
+    if (expr.kind !== "literal" || expr.value.kind !== "str") {
+      return err(
+        "inline assembly instruction must be string literal with instruction",
+        expr.span,
+      );
+    }
+    const text = expr.value.value;
+    const parts = text.split(" ");
+    const imms = parts.slice(1);
+    const wasmInstr = INSTRS.find((instrVal) => instrVal.name === parts[0]);
+    if (!wasmInstr) {
+      return err(`unknown instruction: ${parts[0]}`, expr.span);
+    }
+    if (wasmInstr.immediates === "select") {
+      throw new Error("todo: select");
+    } else if (wasmInstr.immediates === "memarg") {
+      throw new Error("todo: memarg");
+    } else {
+      if (imms.length !== wasmInstr.immediates.length) {
+        return err(
+          `mismatched immediate lengths, expected ${wasmInstr.immediates.length}, got ${imms.length}`,
+          expr.span,
+        );
+      }
+      if (wasmInstr.immediates.length > 1) {
+        throw new Error("todo: immediates");
+      }
+
+      if (wasmInstr.immediates.length === 0) {
+        instructions.push({ kind: wasmInstr.name } as Instr);
+      } else {
+        instructions.push({
+          kind: wasmInstr.name,
+          imm: Number(imms[0]),
+        } as Instr);
+      }
+    }
+  }
+
+  return { kind: "asm", locals, ty: retTy, instructions, span: body.span };
+}
+
 function checkLValue(cx: TypeckCtx, expr: Expr<Typecked>) {
   switch (expr.kind) {
     case "ident":
@@ -641,21 +735,19 @@ function checkCall(
   fcx: FuncCtx,
   expr: ExprCall<Resolved> & Expr<Resolved>,
 ): Expr<Typecked> {
-  if (
-    expr.lhs.kind === "ident" &&
-    expr.lhs.value.res.kind === "builtin" &&
-    expr.lhs.value.res.name === "___transmute"
-  ) {
-    const ty = fcx.infcx.newVar();
-    const args = expr.args.map((arg) => fcx.checkExpr(arg));
-    const ret: Expr<Typecked> = {
-      ...expr,
-      lhs: { ...expr.lhs, ty: TY_UNIT },
-      args,
-      ty,
-    };
+  if (expr.lhs.kind === "ident" && expr.lhs.value.res.kind === "builtin") {
+    if (expr.lhs.value.res.name === "___transmute") {
+      const ty = fcx.infcx.newVar();
+      const args = expr.args.map((arg) => fcx.checkExpr(arg));
+      const ret: Expr<Typecked> = {
+        ...expr,
+        lhs: { ...expr.lhs, ty: TY_UNIT },
+        args,
+        ty,
+      };
 
-    return ret;
+      return ret;
+    }
   }
 
   const lhs = fcx.checkExpr(expr.lhs);
diff --git a/src/wasm/defs.ts b/src/wasm/defs.ts
index 1cb8fcd..aa917ca 100644
--- a/src/wasm/defs.ts
+++ b/src/wasm/defs.ts
@@ -19,6 +19,15 @@ export type Vectype = "v128";
 export type Reftype = "funcref" | "externref";
 
 export type ValType = Numtype | Vectype | Reftype;
+export const VALTYPES: ValType[] = [
+  "i32",
+  "i64",
+  "f32",
+  "f64",
+  "v128",
+  "funcref",
+  "externref",
+];
 
 export type ResultType = ValType[];
 
@@ -66,11 +75,25 @@ export type Externtype =
 
 // instructions
 
+// Value representations of the types for the assembler
+export type InstrValue = {
+  name: Instr["kind"];
+  immediates: ImmediateValue[] | "select" | "memarg";
+};
+type ImmediateValue = "i32" | "i64" | "f32" | "f64" | "refkind";
+
+const ins = (name: Instr["kind"], immediates: InstrValue["immediates"]) => ({
+  name,
+  immediates,
+});
+
 // . numeric
 
 export type BitWidth = "32" | "64";
+const BIT_WIDTHS: BitWidth[] = ["32", "64"];
 
 export type Sign = "u" | "s";
+const SIGNS: Sign[] = ["u", "s"];
 
 export type NumericInstr =
   | { kind: "i32.const"; imm: bigint }
@@ -86,7 +109,7 @@ export type NumericInstr =
   | { kind: `f${BitWidth}.${FRelOp}` }
   | { kind: `i${BitWidth}.extend8_s` }
   | { kind: `i${BitWidth}.extend16_s` }
-  | { kind: `i64.extend32_s` }
+  | { kind: "i64.extend32_s" }
   | { kind: "i32.wrap_i64" }
   | { kind: `i64.extend_i32_${Sign}` }
   | { kind: `i${BitWidth}.trunc_f${BitWidth}_${Sign}` }
@@ -98,6 +121,7 @@ export type NumericInstr =
   | { kind: "f32.reinterpret_i32" | "f64.reinterpret_i64" };
 
 export type IUnOp = "clz" | "ctz" | "popcnt";
+const I_UN_OPS: IUnOp[] = ["clz", "ctz", "popcnt"];
 
 export type IBinOp =
   | "add"
@@ -112,19 +136,47 @@ export type IBinOp =
   | `shr_${Sign}`
   | "rotl"
   | "rotr";
+const I_BIN_OPS: IBinOp[] = [
+  "add",
+  "sub",
+  "mul",
+  "and",
+  "or",
+  "xor",
+  "shl",
+  "rotl",
+  "rotr",
+  ...SIGNS.flatMap((sign): IBinOp[] => [
+    `div_${sign}`,
+    `rem_${sign}`,
+    `shr_${sign}`,
+  ]),
+];
 
-export type FUnOp =
-  | "abs"
-  | "neg"
-  | "sqrt"
-  | "ceil"
-  | "floor"
-  | "trunc"
-  | "nearest";
+const F_UN_OPS = [
+  "abs",
+  "neg",
+  "sqrt",
+  "ceil",
+  "floor",
+  "trunc",
+  "nearest",
+] as const;
+export type FUnOp = (typeof F_UN_OPS)[number];
 
-export type FBinOp = "add" | "sub" | "mul" | "div" | "min" | "max" | "copysign";
+const F_BIN_OPS = [
+  "add",
+  "sub",
+  "mul",
+  "div",
+  "min",
+  "max",
+  "copysign",
+] as const;
+export type FBinOp = (typeof F_BIN_OPS)[number];
 
-export type ITestOp = "eqz";
+const I_TEST_OPS = ["eqz"] as const;
+export type ITestOp = (typeof I_TEST_OPS)[number];
 
 export type IRelOp =
   | "eq"
@@ -133,12 +185,62 @@ export type IRelOp =
   | `gt_${Sign}`
   | `le_${Sign}`
   | `ge_${Sign}`;
+const I_REL_OPS: IRelOp[] = [
+  "eq",
+  "ne",
+  ...SIGNS.flatMap((sign): IRelOp[] => [
+    `lt_${sign}`,
+    `gt_${sign}`,
+    `le_${sign}`,
+    `ge_${sign}`,
+  ]),
+];
 
-export type FRelOp = "eq" | "ne" | "lt" | "gt" | "le" | "ge";
+const F_REL_OPS = ["eq", "ne", "lt", "gt", "le", "ge"] as const;
+export type FRelOp = (typeof F_REL_OPS)[number];
+
+const NO_IMM_NUMERIC_INSTRS: NumericInstr["kind"][] = [
+  ...BIT_WIDTHS.flatMap((bitWidth): NumericInstr["kind"][] => [
+    ...I_UN_OPS.map((op): NumericInstr["kind"] => `i${bitWidth}.${op}`),
+    ...F_UN_OPS.map((op): NumericInstr["kind"] => `f${bitWidth}.${op}`),
+    ...I_BIN_OPS.map((op): NumericInstr["kind"] => `i${bitWidth}.${op}`),
+    ...F_BIN_OPS.map((op): NumericInstr["kind"] => `f${bitWidth}.${op}`),
+    ...I_TEST_OPS.map((op): NumericInstr["kind"] => `i${bitWidth}.${op}`),
+    ...I_REL_OPS.map((op): NumericInstr["kind"] => `i${bitWidth}.${op}`),
+    ...F_REL_OPS.map((op): NumericInstr["kind"] => `f${bitWidth}.${op}`),
+    `i${bitWidth}.extend8_s`,
+    `i${bitWidth}.extend16_s`,
+    ...BIT_WIDTHS.flatMap((bitWidth2): NumericInstr["kind"][] =>
+      SIGNS.flatMap((sign): NumericInstr["kind"][] => [
+        `i${bitWidth}.trunc_f${bitWidth2}_${sign}`,
+        `i${bitWidth}.trunc_sat_f${bitWidth2}_${sign}`,
+        `f${bitWidth}.convert_i${bitWidth2}_${sign}`,
+      ]),
+    ),
+  ]),
+  "i64.extend32_s",
+  "i32.wrap_i64",
+  ...SIGNS.flatMap((sign): NumericInstr["kind"] => `i64.extend_i32_${sign}`),
+  "f32.demote_f64",
+  "f64.promote_f32",
+  "i32.reinterpret_f32",
+  "i64.reinterpret_f64",
+  "f32.reinterpret_i32",
+  "f64.reinterpret_i64",
+];
+const IMM_NUMERIC_INSTRS: InstrValue[] = (
+  ["i32", "i64", "f32", "f64"] as const
+).map((type) => ins(`${type}.const`, [type]));
+
+const NUMERIC_INSTRS: InstrValue[] = [
+  ...NO_IMM_NUMERIC_INSTRS.map((instr) => ins(instr, [])),
+  ...IMM_NUMERIC_INSTRS,
+];
 
 // . vectors
 
 export type VectorInstr = never;
+const VECTOR_INSTRS: InstrValue[] = [];
 
 // . reference
 
@@ -146,12 +248,21 @@ export type ReferenceInstr =
   | { kind: "ref.null"; imm: Reftype }
   | { kind: "ref.is_null" }
   | { kind: "ref.func"; imm: FuncIdx };
+const REFERENCE_INSTRS: InstrValue[] = [
+  ins("ref.null", ["refkind"]),
+  ins("ref.is_null", []),
+  ins("ref.func", ["i32"]),
+];
 
 // . parametric
 
 export type ParametricInstr =
   | { kind: "drop" }
   | { kind: "select"; type?: ValType[] };
+const PARAMETRIC_INSTRS: InstrValue[] = [
+  ins("drop", []),
+  ins("select", "select"),
+];
 
 // . variable
 
@@ -164,6 +275,12 @@ export type VariableInstr =
       kind: `global.${"get" | "set"}`;
       imm: LocalIdx;
     };
+const VARIABLE_INSTR: InstrValue[] = [
+  ...(["get", "set", "tee"] as const).map((kind) =>
+    ins(`local.${kind}`, ["i32"]),
+  ),
+  ...(["get", "set"] as const).map((kind) => ins(`global.${kind}`, ["i32"])),
+];
 
 // . table
 
@@ -186,6 +303,14 @@ export type TableInstr =
       kind: "elem.drop";
       imm: ElemIdx;
     };
+const TABLE_INSTRS: InstrValue[] = [
+  ...(["get", "set", "size", "grow", "fill"] as const).map((kind) =>
+    ins(`table.${kind}`, ["i32"]),
+  ),
+  ins("table.copy", ["i32", "i32"]),
+  ins("table.init", ["i32", "i32"]),
+  ins("elem.drop", ["i32"]),
+];
 
 // . memory
 
@@ -197,6 +322,18 @@ export type MemArg = {
 export type SimpleStoreKind = `${`${"i" | "f"}${BitWidth}` | "v128"}.${
   | "load"
   | "store"}`;
+const SIMPLE_STORES: SimpleStoreKind[] = [
+  "i32.load",
+  "i32.store",
+  "f32.load",
+  "f32.store",
+  "i64.load",
+  "i64.store",
+  "f64.load",
+  "f64.store",
+  "v128.load",
+  "v128.store",
+];
 
 export type MemoryInstr =
   | {
@@ -221,6 +358,35 @@ export type MemoryInstr =
       imm: DataIdx;
     }
   | { kind: "data.drop"; imm: DataIdx };
+const MEMORY_INSTRS_WITH_MEMARG: MemoryInstr["kind"][] = [
+  ...SIMPLE_STORES,
+  "i32.load8_u",
+  "i32.load8_s",
+  "i32.load16_u",
+  "i32.load16_s",
+  "i64.load8_u",
+  "i64.load8_s",
+  "i64.load16_u",
+  "i64.load16_s",
+  //
+  "i64.load32_u",
+  "i64.load32_s",
+  //
+  "i32.store8",
+  "i32.store16",
+  "i64.store8",
+  "i64.store16",
+  "i64.store32",
+];
+const MEMORY_INSTRS: InstrValue[] = [
+  ...MEMORY_INSTRS_WITH_MEMARG.map((kind) => ins(kind, "memarg")),
+  ins("memory.size", []),
+  ins("memory.grow", []),
+  ins("memory.fill", []),
+  ins("memory.copy", []),
+  ins("memory.init", ["i32"]),
+  ins("data.drop", ["i32"]),
+];
 
 // . control
 
@@ -278,6 +444,16 @@ export type Instr =
   | MemoryInstr
   | ControlInstr;
 
+export const INSTRS: InstrValue[] = [
+  ...NUMERIC_INSTRS,
+  ...VECTOR_INSTRS,
+  ...REFERENCE_INSTRS,
+  ...PARAMETRIC_INSTRS,
+  ...VARIABLE_INSTR,
+  ...TABLE_INSTRS,
+  ...MEMORY_INSTRS,
+];
+
 export type Expr = Instr[];
 
 // Modules
diff --git a/ui-tests/asm/drop.nil b/ui-tests/asm/drop.nil
new file mode 100644
index 0000000..6025e29
--- /dev/null
+++ b/ui-tests/asm/drop.nil
@@ -0,0 +1,10 @@
+//@check-pass
+
+function dropping(a: I32) =
+    ___asm(
+        __locals(),
+        "local.get 0",
+        "drop",
+    );
+
+function main() = ;
diff --git a/ui-tests/asm/instr_not_string.nil b/ui-tests/asm/instr_not_string.nil
new file mode 100644
index 0000000..2ac1287
--- /dev/null
+++ b/ui-tests/asm/instr_not_string.nil
@@ -0,0 +1,7 @@
+function a(a: I32) =
+    ___asm(
+        __locals(),
+        0,
+    );
+
+function main() = ;
diff --git a/ui-tests/asm/instr_not_string.stderr b/ui-tests/asm/instr_not_string.stderr
new file mode 100644
index 0000000..1a146bd
--- /dev/null
+++ b/ui-tests/asm/instr_not_string.stderr
@@ -0,0 +1,4 @@
+error: inline assembly instruction must be string literal with instruction
+ --> $DIR/instr_not_string.nil:4
+4 |         0,
+            ^
diff --git a/ui-tests/asm/invalid_instr.nil b/ui-tests/asm/invalid_instr.nil
new file mode 100644
index 0000000..c6a1ed0
--- /dev/null
+++ b/ui-tests/asm/invalid_instr.nil
@@ -0,0 +1,9 @@
+//@check-pass
+
+function dropping(a: I32) =
+    ___asm(
+        __locals(),
+        "meow meow",
+    );
+
+function main() = ;
diff --git a/ui-tests/asm/invalid_instr.stderr b/ui-tests/asm/invalid_instr.stderr
new file mode 100644
index 0000000..d2345d7
--- /dev/null
+++ b/ui-tests/asm/invalid_instr.stderr
@@ -0,0 +1,4 @@
+error: unknown instruction: meow
+ --> $DIR/invalid_instr.nil:6
+6 |         "meow meow",
+            ^^^^^^^^^^^
diff --git a/ui-tests/asm/missing_locals.nil b/ui-tests/asm/missing_locals.nil
new file mode 100644
index 0000000..20eef07
--- /dev/null
+++ b/ui-tests/asm/missing_locals.nil
@@ -0,0 +1,9 @@
+//@check-pass
+
+function dropping(a: I32) =
+    ___asm(
+        "local.get 0",
+        "drop",
+    );
+
+function main() = ;
diff --git a/ui-tests/asm/missing_locals.stderr b/ui-tests/asm/missing_locals.stderr
new file mode 100644
index 0000000..2d91691
--- /dev/null
+++ b/ui-tests/asm/missing_locals.stderr
@@ -0,0 +1,4 @@
+error: inline assembly must have __locals() as first argument
+ --> $DIR/missing_locals.nil:4
+4 |     ___asm(
+              ^
diff --git a/ui-tests/asm/not_toplevel.nil b/ui-tests/asm/not_toplevel.nil
new file mode 100644
index 0000000..438304e
--- /dev/null
+++ b/ui-tests/asm/not_toplevel.nil
@@ -0,0 +1,6 @@
+function dropping(a: I32) = (
+    1;
+    ___asm(__locals(), "drop");
+);
+
+function main() = ;
diff --git a/ui-tests/asm/not_toplevel.stderr b/ui-tests/asm/not_toplevel.stderr
new file mode 100644
index 0000000..d6f6444
--- /dev/null
+++ b/ui-tests/asm/not_toplevel.stderr
@@ -0,0 +1,16 @@
+error: `___asm` cannot be used as a value
+ --> $DIR/not_toplevel.nil:3
+3 |     ___asm(__locals(), "drop");
+        ^^^^^^
+error: `__locals` cannot be used as a value
+ --> $DIR/not_toplevel.nil:3
+3 |     ___asm(__locals(), "drop");
+               ^^^^^^^^
+error: expression of type <ERROR> is not callable
+ --> $DIR/not_toplevel.nil:3
+3 |     ___asm(__locals(), "drop");
+               ^^^^^^^^
+error: expression of type <ERROR> is not callable
+ --> $DIR/not_toplevel.nil:3
+3 |     ___asm(__locals(), "drop");
+        ^^^^^^
diff --git a/ui-tests/asm/wrong_imm.nil b/ui-tests/asm/wrong_imm.nil
new file mode 100644
index 0000000..7a4dc80
--- /dev/null
+++ b/ui-tests/asm/wrong_imm.nil
@@ -0,0 +1,17 @@
+//@check-pass
+
+function a(a: I32) =
+    ___asm(
+        __locals(),
+        "local.get 0 0",
+        "drop",
+    );
+
+function b(a: I32) =
+    ___asm(
+        __locals(),
+        "local.get",
+        "drop",
+    );
+
+function main() = ;
diff --git a/ui-tests/asm/wrong_imm.stderr b/ui-tests/asm/wrong_imm.stderr
new file mode 100644
index 0000000..c94c14f
--- /dev/null
+++ b/ui-tests/asm/wrong_imm.stderr
@@ -0,0 +1,8 @@
+error: mismatched immediate lengths, expected 1, got 2
+ --> $DIR/wrong_imm.nil:6
+6 |         "local.get 0 0",
+            ^^^^^^^^^^^^^^^
+error: mismatched immediate lengths, expected 1, got 0
+ --> $DIR/wrong_imm.nil:13
+13 |         "local.get",
+             ^^^^^^^^^^^
diff --git a/ui-tests/type/generics/generics_structs_in_args.stderr b/ui-tests/type/generics/generics_structs_in_args.stderr
new file mode 100644
index 0000000..f4499a9
--- /dev/null
+++ b/ui-tests/type/generics/generics_structs_in_args.stderr
@@ -0,0 +1,17 @@
+/home/nils/projects/riverdelta/target/ast.js:110
+                throw new Error(`substitution out of range, param index ${ty.idx} of param ${ty.name} out of range for length ${genericArgs.length}`);
+                ^
+
+Error: substitution out of range, param index 0 of param T out of range for length 0
+    at substituteTy (/home/nils/projects/riverdelta/target/ast.js:110:23)
+    at subst (/home/nils/projects/riverdelta/target/ast.js:106:27)
+    at Array.map (<anonymous>)
+    at substituteTy (/home/nils/projects/riverdelta/target/ast.js:125:45)
+    at typeOfItem (/home/nils/projects/riverdelta/target/typeck/item.js:193:33)
+    at Object.itemInner (/home/nils/projects/riverdelta/target/typeck/index.js:63:54)
+    at Object.item (/home/nils/projects/riverdelta/target/ast.js:146:34)
+    at /home/nils/projects/riverdelta/target/ast.js:164:55
+    at Array.map (<anonymous>)
+    at foldAst (/home/nils/projects/riverdelta/target/ast.js:164:34)
+
+Node.js v18.18.2