Fix type confusion when resolving nested generics

src/compiler.ts

@@ -6438,7 +6438,7 @@ export class Compiler extends DiagnosticEmitter {
         assert(typeParameterNodes),
         typeArgumentNodes,
         this.currentFlow.actualFunction.parent,
-        uniqueMap<string,Type>(this.currentFlow.contextualTypeArguments),
+        uniqueMap<string,Type>(this.currentFlow.contextualTypeArguments), // don't update
         expression
       );
     }

src/resolver.ts

@@ -306,7 +306,7 @@ export class Resolver extends DiagnosticEmitter {
           typeParameterNodes,
           typeArgumentNodes,
           ctxElement,
-          ctxTypes = uniqueMap(ctxTypes), // inherit
+          ctxTypes = uniqueMap(ctxTypes), // update
           node,
           reportMode
         );
@@ -644,7 +644,7 @@ export class Resolver extends DiagnosticEmitter {
     typeArgumentNodes: TypeNode[] | null,
     /** Contextual element. */
     ctxElement: Element,
-    /** Contextual types, i.e. `T`. */
+    /** Contextual types, i.e. `T`. Updated in place with the new set of contextual types. */
     ctxTypes: Map<string,Type> = uniqueMap<string,Type>(),
     /** Alternative report node in case of empty type arguments. */
     alternativeReportNode: Node | null = null,
@@ -675,18 +675,20 @@ export class Resolver extends DiagnosticEmitter {
       return null;
     }
     var typeArguments = new Array<Type>(maxParameterCount);
+    var oldCtxTypes = uniqueMap<string,Type>(ctxTypes);
+    ctxTypes.clear();
     for (let i = 0; i < maxParameterCount; ++i) {
       let type = i < argumentCount
         ? this.resolveType( // reports
             typeArgumentNodes![i],
             ctxElement,
-            ctxTypes,
+            oldCtxTypes, // update
             reportMode
           )
         : this.resolveType( // reports
             assert(typeParameters[i].defaultType),
             ctxElement,
-            ctxTypes,
+            uniqueMap<string,Type>(ctxTypes), // don't update
             reportMode
           );
       if (!type) return null;
@@ -2796,7 +2798,7 @@ export class Resolver extends DiagnosticEmitter {
         assert(prototype.typeParameterNodes),
         typeArgumentNodes,
         ctxElement,
-        ctxTypes,
+        ctxTypes, // update
         reportNode,
         reportMode
       );
@@ -3272,7 +3274,7 @@ export class Resolver extends DiagnosticEmitter {
         assert(prototype.typeParameterNodes), // must be present if generic
         typeArgumentNodes,
         ctxElement,
-        ctxTypes,
+        ctxTypes, // update
         reportNode,
         reportMode
       );

tests/compiler/issues/1714.optimized.wat

@@ -0,0 +1,8 @@
+(module
+ (memory $0 1)
+ (data (i32.const 1036) ",")
+ (data (i32.const 1048) "\01\00\00\00\1c\00\00\00i\00s\00s\00u\00e\00s\00/\001\007\001\004\00.\00t\00s")
+ (data (i32.const 1084) "\1c")
+ (data (i32.const 1096) "\01\00\00\00\06\00\00\00i\003\002")
+ (export "memory" (memory $0))
+)

tests/compiler/issues/1714.ts

@@ -0,0 +1,18 @@
+function a_i64_i32<T,U>(): bool { // T'=U=i64, U'=T=i32
+  return sizeof<T>() == sizeof<U>();
+}
+
+function foo<T,U>(): bool { // T=i32, U=i64
+  return a_i64_i32<U,T>() == true;
+}
+
+assert(foo<i32, i64>() == false);
+
+function bar<T1,T2>(): string { // T1=f64, T2=i32
+  if (isInteger<T2>()) {
+    return bar<T2,T1>(); // T2'=T1=f64, T2'=T1=i32
+  }
+  return nameof<T1>(); // iff T1 == i32
+}
+
+assert(bar<f64, i32>() === "i32");

tests/compiler/issues/1714.untouched.wat

@@ -0,0 +1,65 @@
+(module
+ (type $none_=>_i32 (func (result i32)))
+ (type $none_=>_none (func))
+ (type $i32_i32_i32_i32_=>_none (func (param i32 i32 i32 i32)))
+ (import "env" "abort" (func $~lib/builtins/abort (param i32 i32 i32 i32)))
+ (memory $0 1)
+ (data (i32.const 12) ",\00\00\00\00\00\00\00\00\00\00\00\01\00\00\00\1c\00\00\00i\00s\00s\00u\00e\00s\00/\001\007\001\004\00.\00t\00s\00")
+ (data (i32.const 60) "\1c\00\00\00\00\00\00\00\00\00\00\00\01\00\00\00\06\00\00\00i\003\002\00\00\00\00\00\00\00")
+ (table $0 1 funcref)
+ (global $~lib/memory/__data_end i32 (i32.const 92))
+ (global $~lib/memory/__stack_pointer (mut i32) (i32.const 16476))
+ (global $~lib/memory/__heap_base i32 (i32.const 16476))
+ (export "memory" (memory $0))
+ (start $~start)
+ (func $issues/1714/a_i64_i32<i64,i32> (result i32)
+  i32.const 8
+  i32.const 4
+  i32.eq
+ )
+ (func $issues/1714/foo<i32,i64> (result i32)
+  call $issues/1714/a_i64_i32<i64,i32>
+  i32.const 1
+  i32.eq
+ )
+ (func $issues/1714/bar<i32,f64> (result i32)
+  i32.const 0
+  drop
+  i32.const 80
+ )
+ (func $issues/1714/bar<f64,i32> (result i32)
+  i32.const 1
+  drop
+  call $issues/1714/bar<i32,f64>
+  return
+ )
+ (func $start:issues/1714
+  call $issues/1714/foo<i32,i64>
+  i32.const 0
+  i32.eq
+  i32.eqz
+  if
+   i32.const 0
+   i32.const 32
+   i32.const 9
+   i32.const 1
+   call $~lib/builtins/abort
+   unreachable
+  end
+  call $issues/1714/bar<f64,i32>
+  i32.const 80
+  i32.eq
+  i32.eqz
+  if
+   i32.const 0
+   i32.const 32
+   i32.const 18
+   i32.const 1
+   call $~lib/builtins/abort
+   unreachable
+  end
+ )
+ (func $~start
+  call $start:issues/1714
+ )
+)