Merge pull request #1008 from WalterSmuts/exhaustive-branch-returns

Exhaustive branch returns
hylo-lang · Sep 15, 2023 · 4304044 · 4304044
2 parents d04d402 + b076201
commit 4304044
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Showing 3 changed files with 27 additions and 9 deletions.
diff --git a/Sources/IR/Analysis/Module+NormalizeObjectStates.swift b/Sources/IR/Analysis/Module+NormalizeObjectStates.swift
@@ -534,6 +534,16 @@ extension Module {
         if o.value == .full(.initialized) { return }
 
         if k == .set {
+          // If the parameter is a return value (index == 0) we emit specialized diagnostics.
+          if case .parameter(_, 0) = p {
+            let t = self[f].output
+            if !t.isVoidOrNever {
+              diagnostics.insert(
+                .missingFunctionReturn(expectedReturnType: t, at: site)
+              )
+              return
+            }
+          }
           diagnostics.insert(
             .uninitializedSetParameter(beforeReturningFrom: f, in: self, at: site))
           return
@@ -991,4 +1001,11 @@ extension Diagnostic {
     .error("use of uninitialized object", at: site)
   }
 
+  fileprivate static func missingFunctionReturn(
+    expectedReturnType: AnyType,
+    at site: SourceRange
+  ) -> Diagnostic {
+    .error("missing return in function expected to return '\(expectedReturnType)'", at: site)
+  }
+
 }
diff --git a/Sources/IR/Emitter.swift b/Sources/IR/Emitter.swift
@@ -233,9 +233,7 @@ struct Emitter {
   ) -> SourceRange {
     switch emit(braceStmt: b) {
     case .next:
-      if !canonical(returnType).isVoidOrNever {
-        report(.error(missingReturn: returnType, at: .empty(atEndOf: ast[b].site)))
-      } else {
+      if canonical(returnType).isVoidOrNever {
         emitStore(value: .void, to: returnValue!, at: .empty(atEndOf: ast[b].site))
       }
       return ast[b].site
@@ -2609,12 +2607,6 @@ extension Diagnostic {
     .error("integer literal '\(s)' overflows when stored into '\(t)'", at: site)
   }
 
-  fileprivate static func error(
-    missingReturn returnType: AnyType, at site: SourceRange
-  ) -> Diagnostic {
-    .error("missing return in function expected to return '\(returnType)'", at: site)
-  }
-
   fileprivate static func warning(unreachableStatement s: AnyStmtID, in ast: AST) -> Diagnostic {
     .error("statement will never be executed", at: .empty(at: ast[s].site.first()))
   }

diff --git a/Tests/EndToEndTests/TestCases/ExhaustiveBranchReturns.hylo b/Tests/EndToEndTests/TestCases/ExhaustiveBranchReturns.hylo
@@ -0,0 +1,9 @@
+//- compileAndRun expecting: success
+
+public fun main() {
+  let _ = f()
+}
+
+public fun f() -> Int {
+  if true { return 0 } else { return 1 }
+}