Skip inlining and emit a warning when trying to inline a function into itself

src/builtins.ts

@@ -54,7 +54,6 @@ import {
 import {
   ReportMode
 } from "./resolver";
-import { CommonFlags } from "./common";
 
 /** Compiles a call to a built-in function. */
 export function compileCall(
@@ -73,7 +72,7 @@ export function compileCall(
       ret: ExpressionRef;
 
   // NOTE that some implementations below make use of the select expression where straight-forward.
-  // whether worth or not should probably be tested once/ it's known if/how embedders handle it.
+  // whether worth or not should probably be tested once it's known if/how embedders handle it.
   // search: createSelect
 
   switch (prototype.internalName) {

src/compiler.ts

@@ -265,6 +265,8 @@ export class Compiler extends DiagnosticEmitter {
   currentFunction: Function;
   /** Current outer function in compilation, if compiling a function expression. */
   currentOuterFunction: Function | null = null;
+  /** Current inline function in compilation. */
+  currentInlineFunction: Function | null = null;
   /** Current enum in compilation. */
   currentEnum: Enum | null = null;
   /** Current type in compilation. */
@@ -5257,7 +5259,21 @@ export class Compiler extends DiagnosticEmitter {
     // Inline if explicitly requested
     if (inline) {
       assert(!instance.is(CommonFlags.TRAMPOLINE)); // doesn't make sense
-      return this.compileCallInlineUnchecked(instance, argumentExpressions, reportNode, thisArg);
+      if (instance === this.currentInlineFunction) {
+        // skip inlining when trying to inline a function into itself and print a warning when
+        // instead compiling the function the normal way.
+        if (instance === this.currentFunction) {
+          this.warning(
+            DiagnosticCode.Function_0_cannot_be_inlined_into_itself,
+            reportNode.range, instance.internalName
+          );
+        }
+      } else {
+        this.currentInlineFunction = instance;
+        let ret = this.compileCallInlineUnchecked(instance, argumentExpressions, reportNode, thisArg);
+        this.currentInlineFunction = null;
+        return ret;
+      }
     }
 
     // Otherwise compile to just a call

src/diagnosticMessages.generated.ts

@@ -26,6 +26,7 @@ export enum DiagnosticCode {
   An_allocator_must_be_declared_to_allocate_memory_Try_importing_allocator_arena_or_allocator_tlsf = 214,
   Optional_parameter_must_have_an_initializer = 215,
   Constructor_of_class_0_must_not_require_any_arguments = 216,
+  Function_0_cannot_be_inlined_into_itself = 217,
   Unterminated_string_literal = 1002,
   Identifier_expected = 1003,
   _0_expected = 1005,
@@ -142,6 +143,7 @@ export function diagnosticCodeToString(code: DiagnosticCode): string {
     case 214: return "An allocator must be declared to allocate memory. Try importing allocator/arena or allocator/tlsf.";
     case 215: return "Optional parameter must have an initializer.";
     case 216: return "Constructor of class '{0}' must not require any arguments.";
+    case 217: return "Function '{0}' cannot be inlined into itself.";
     case 1002: return "Unterminated string literal.";
     case 1003: return "Identifier expected.";
     case 1005: return "'{0}' expected.";

src/diagnosticMessages.json

@@ -18,6 +18,7 @@
   "An allocator must be declared to allocate memory. Try importing allocator/arena or allocator/tlsf.": 214,
   "Optional parameter must have an initializer.": 215,
   "Constructor of class '{0}' must not require any arguments.": 216,
+  "Function '{0}' cannot be inlined into itself.": 217,
 
   "Unterminated string literal.": 1002,
   "Identifier expected.": 1003,