4 files changed, 137 insertions, 7 deletions
diff --git a/src/cmd/compile/internal/escape/escape.go b/src/cmd/compile/internal/escape/escape.go
index 06dee7ec41..a39d6b49a6 100644
--- a/src/cmd/compile/internal/escape/escape.go
+++ b/src/cmd/compile/internal/escape/escape.go
@@ -545,6 +545,14 @@ func (b *batch) rewriteWithLiterals(n ir.Node, fn *ir.Func) {
 		base.Fatalf("no ReassignOracle for function %v with closure parent %v", fn, fn.ClosureParent)
 	}
 
+	assignTemp := func(n ir.Node, init *ir.Nodes) {
+		// Preserve any side effects of n by assigning it to an otherwise unused temp.
+		pos := n.Pos()
+		tmp := typecheck.TempAt(pos, fn, n.Type())
+		init.Append(typecheck.Stmt(ir.NewDecl(pos, ir.ODCL, tmp)))
+		init.Append(typecheck.Stmt(ir.NewAssignStmt(pos, tmp, n)))
+	}
+
 	switch n.Op() {
 	case ir.OMAKESLICE:
 		// Check if we can replace a non-constant argument to make with
@@ -556,13 +564,17 @@ func (b *batch) rewriteWithLiterals(n ir.Node, fn *ir.Func) {
 			r = &n.Len
 		}
 
-		if s := ro.StaticValue(*r); s.Op() == ir.OLITERAL {
-			lit, ok := s.(*ir.BasicLit)
-			if !ok || lit.Val().Kind() != constant.Int {
-				base.Fatalf("unexpected BasicLit Kind")
-			}
-			if constant.Compare(lit.Val(), token.GEQ, constant.MakeInt64(0)) {
-				*r = lit
+		if (*r).Op() != ir.OLITERAL {
+			if s := ro.StaticValue(*r); s.Op() == ir.OLITERAL {
+				lit, ok := s.(*ir.BasicLit)
+				if !ok || lit.Val().Kind() != constant.Int {
+					base.Fatalf("unexpected BasicLit Kind")
+				}
+				if constant.Compare(lit.Val(), token.GEQ, constant.MakeInt64(0)) {
+					// Preserve any side effects of the original expression, then replace it.
+					assignTemp(*r, n.PtrInit())
+					*r = lit
+				}
 			}
 		}
 	case ir.OCONVIFACE:
@@ -575,6 +587,8 @@ func (b *batch) rewriteWithLiterals(n ir.Node, fn *ir.Func) {
 				if base.Debug.EscapeDebug >= 3 {
 					base.WarnfAt(n.Pos(), "rewriting OCONVIFACE value from %v (%v) to %v (%v)", conv.X, conv.X.Type(), v, v.Type())
 				}
+				// Preserve any side effects of the original expression, then replace it.
+				assignTemp(conv.X, conv.PtrInit())
 				v := v.(*ir.BasicLit)
 				conv.X = ir.NewBasicLit(conv.X.Pos(), conv.X.Type(), v.Val())
 				typecheck.Expr(conv)
diff --git a/test/fixedbugs/issue74379.go b/test/fixedbugs/issue74379.go
new file mode 100644
index 0000000000..e516505fbe
--- /dev/null
+++ b/test/fixedbugs/issue74379.go
@@ -0,0 +1,30 @@
+// run
+
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+)
+
+func crashOnErr(err error) bool {
+	if err != nil {
+		panic(err)
+	}
+	return false
+}
+
+func main() {
+	defer func() {
+		if recover() == nil {
+			fmt.Println("failed to have expected panic")
+			os.Exit(1)
+		}
+	}()
+	fmt.Println(crashOnErr(errors.New("test error")))
+}
diff --git a/test/fixedbugs/issue74379b.go b/test/fixedbugs/issue74379b.go
new file mode 100644
index 0000000000..2603587914
--- /dev/null
+++ b/test/fixedbugs/issue74379b.go
@@ -0,0 +1,32 @@
+// run
+
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+)
+
+func crashOnErr(err error) int {
+	if err != nil {
+		panic(err)
+	}
+	return 10
+}
+
+func main() {
+	defer func() {
+		if recover() == nil {
+			fmt.Println("failed to have expected panic")
+			os.Exit(1)
+		}
+	}()
+
+	s := make([]int, crashOnErr(errors.New("test error")))
+	println("unreachable: len(s) =", len(s))
+}
diff --git a/test/fixedbugs/issue74379c.go b/test/fixedbugs/issue74379c.go
new file mode 100644
index 0000000000..871307bf89
--- /dev/null
+++ b/test/fixedbugs/issue74379c.go
@@ -0,0 +1,54 @@
+// run
+
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+)
+
+type S struct{ a, b int }
+
+func crashOnErr1(err error) S {
+	if err != nil {
+		panic(err)
+	}
+	return S{} // zero value struct
+}
+
+func f1() {
+	defer func() {
+		if recover() == nil {
+			fmt.Println("failed to have expected panic")
+			os.Exit(1)
+		}
+	}()
+	fmt.Println(crashOnErr1(errors.New("test error")))
+}
+
+func crashOnErr2(err error) S {
+	if err != nil {
+		panic(err)
+	}
+	return S{1, 2} // not zero value struct
+}
+
+func f2() {
+	defer func() {
+		if recover() == nil {
+			fmt.Println("failed to have expected panic")
+			os.Exit(1)
+		}
+	}()
+	fmt.Println(crashOnErr2(errors.New("test error")))
+}
+
+func main() {
+	f1()
+	f2()
+}